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{{short description|'''Climate change and agriculture'''s effectsmay onrefer agriculture}}to:
{{Use British English|date=November 2012}}
{{Use dmy dates|date=September 2021}}
[[File:Greenhouse Gas Emissions by Economic Sector.svg|thumb|upright=1.5|right|Global [[greenhouse gas emissions]] attributed to different economic sectors as per the IPCC AR5 report. 3/4ths of emissions are directly produced, while 1/4th are produced by electricity and heat production that supports the sector.]]
 
* [[Effects of climate change on agriculture]]
'''Climate change and agriculture''' are interrelated processes, both of which take place on a global scale, with the adverse effects of [[climate change]] affecting [[agriculture]] both directly and indirectly. This can take place through changes in [[instrumental temperature record|average temperatures]], [[rain]]fall, and climate [[extreme weather|extremes]] (e.g., [[heat wave]]s); changes in [[pest (organism)|pests]] and [[disease]]s;<ref name="Luck-et-al-2011">{{cite journal | last1=Luck | first1=J. | last2=Spackman | first2=M. | last3=Freeman | first3=A. | last4=Tre˛bicki | first4=P. | last5=Griffiths | first5=W. | last6=Finlay | first6=K. | last7=Chakraborty | first7=S. | title=Climate change and diseases of food crops | journal=[[Plant Pathology (journal)|Plant Pathology]] | publisher=[[British Society for Plant Pathology]] ([[Wiley-Blackwell]]) | volume=60 | issue=1 | date=10 January 2011 | issn=0032-0862 | doi=10.1111/j.1365-3059.2010.02414.x | pages=113–121}}</ref> changes in atmospheric [[carbon dioxide]] and ground-level [[ozone]] concentrations; changes in the [[nutrition]]al quality of some foods;<ref name=science-news>{{cite news |first=Susan |last=Milius | name-list-style = vanc |url= https://www.sciencenews.org/article/nutrition-climate-change-top-science-stories-2017-yir |title=Worries grow that climate change will quietly steal nutrients from major food crops|date=13 December 2017|work=[[Science News]]|access-date=21 January 2018}}</ref> and changes in [[current sea level rise|sea level]].<ref>Hoffmann, U., Section B: Agriculture - a key driver and a major victim of global warming, in: Lead Article, in: Chapter 1, in {{harvnb|Hoffmann|2013|pp=3, 5}}</ref>
* [[Greenhouse gas emissions from agriculture]]
 
{{disambiguation|geo}}
Climate change is already affecting agriculture, with effects unevenly distributed across the world.<ref name="porter summary">Porter, J.R., ''et al''., Executive summary, in: [http://ipcc-wg2.gov/AR5/images/uploads/WGIIAR5-Chap7_FINAL.pdf Chapter 7: Food security and food production systems] (archived [https://web.archive.org/web/20141105164634/https://ipcc-wg2.gov/AR5/images/uploads/WGIIAR5-Chap7_FINAL.pdf 5 November 2014]), in {{harvnb|IPCC AR5 WG2 A|2014|pp=488–489}}
</ref> Future climate changes will most likely affect [[crop yield|crop production]] in [[low latitude]] countries negatively, while effects in northern [[latitude]]s may be positive or negative.<ref name="porter summary" /> [[Animal husbandry]] also contributes towards climate change through [[Greenhouse gas|greenhouse gas emissions]].
 
Agriculture contributes towards global warming through [[Human impact on the environment|anthropogenic]] greenhouse gas emissions and by the conversion of non-agricultural land such as [[forest]]s into agricultural land.<ref>Section 4.2: Agriculture's current contribution to greenhouse gas emissions, in: {{harvnb|HLPE|2012|pp=67–69}}
</ref><ref>{{Cite journal|last1=Sarkodie|first1=Samuel A.|last2=Ntiamoah|first2=Evans B.|last3=Li|first3=Dongmei|date=2019|title=Panel heterogeneous distribution analysis of trade and modernized agriculture on CO2 emissions: The role of renewable and fossil fuel energy consumption|journal=Natural Resources Forum|language=en|volume=43|issue=3|pages=135–153|doi=10.1111/1477-8947.12183|issn=1477-8947|doi-access=free}}</ref> In 2010, agriculture, forestry and land-use change were estimated to contribute 20–25% of global annual emissions.<ref>Blanco, G., ''et al''., Section 5.3.5.4: Agriculture, Forestry, Other Land Use, in: [http://report.mitigation2014.org/report/ipcc_wg3_ar5_chapter5.pdf Chapter 5: Drivers, Trends and Mitigation] (archived [https://web.archive.org/web/20141230092610/http://report.mitigation2014.org/report/ipcc_wg3_ar5_chapter5.pdf 30 December 2014)], in: {{harvnb|IPCC AR5 WG3|2014|p=383}} Emissions aggregated using 100-year [[global warming potential]]s from the [[IPCC Second Assessment Report]]</ref> In 2020, the [[European Union]]'s [[Scientific Advice Mechanism]] estimated that the [[food system]] as a whole contributed 37% of total greenhouse gas emissions, and that this figure was on course to increase by 30–40% by 2050 due to population growth and dietary change.<ref>{{Cite book|last=Science Advice for Policy by European Academies|url=https://www.sapea.info/wp-content/uploads/sustainable-food-system-report.pdf|title=A sustainable food system for the European Union|publisher=SAPEA|year=2020|isbn=978-3-9820301-7-3|location=Berlin|pages=39|doi=10.26356/sustainablefood|access-date=14 April 2020|archive-url=https://web.archive.org/web/20200418105107/https://www.sapea.info/wp-content/uploads/sustainable-food-system-report.pdf|archive-date=18 April 2020|url-status=dead}}</ref>
 
A range of policies can reduce the risk of negative climate change impacts on agriculture<ref>Porter, J.R., ''et al''., Section 7.5: Adaptation and Managing Risks in Agriculture and Other Food System Activities, in [http://ipcc-wg2.gov/AR5/images/uploads/WGIIAR5-Chap7_FINAL.pdf Chapter 7: Food security and food production systems] (archived [https://web.archive.org/web/20141105164634/https://ipcc-wg2.gov/AR5/images/uploads/WGIIAR5-Chap7_FINAL.pdf 5 November 2014]), in {{harvnb|IPCC AR5 WG2 A|2014|pp=513–520}}</ref><ref>Oppenheimer, M., ''et al''., Section 19.7. Assessment of Response Strategies to Manage Risks, in: [http://ipcc-wg2.gov/AR5/images/uploads/WGIIAR5-Chap19_FINAL.pdf Chapter 19: Emergent risks and key vulnerabilities] (archived [https://web.archive.org/web/20141105164634/https://ipcc-wg2.gov/AR5/images/uploads/WGIIAR5-Chap19_FINAL.pdf 5 November 2014]), in {{harvnb|IPCC AR5 WG2 A|2014|p=1080}}</ref> and greenhouse gas emissions from the agriculture sector for a more [[sustainable food system]].<ref>SUMMARY AND RECOMMENDATIONS, in: {{harvnb|HLPE|2012|pp=12–23}}</ref><ref>Current climate change policies are described in {{harvnb|Annex I NC|2014}} and {{harvnb|Non-Annex I NC|2014}}</ref><ref>Smith, P., ''et al''., Executive summary, in: [http://report.mitigation2014.org/report/ipcc_wg3_ar5_chapter5.pdf Chapter 5: Drivers, Trends and Mitigation] (archived [https://web.archive.org/web/20141230092610/http://report.mitigation2014.org/report/ipcc_wg3_ar5_chapter5.pdf 30 December 2014)], in: {{harvnb|IPCC AR5 WG3|2014|pp=816–817}}
</ref>
 
{{TOC level|3}}
 
== Greenhouse gas emissions from agriculture ==
{{update section|reason=it needs more recent info e.g. on plowing and soil|date=July 2019}}
[[File:Greenhouse gas emissions from agriculture, by region, 1990-2010.png|thumb|right|upright=2|alt=refer to caption and image description|Greenhouse gas emissions from agriculture, by region, 1990-2010]]
The agricultural sector is a driving force in the gas emissions and land use effects thought to cause climate change. In addition to being a significant user of [[land use|land]] and consumer of [[fossil fuel]], agriculture contributes directly to [[greenhouse gas emissions]] through practices such as rice production and the raising of livestock;<ref>{{cite book|url=http://www.virtualcentre.org/en/library/key_pub/longshad/A0701E00.pdf|title=Livestock's long shadow: environmental issues and options|vauthors=Steinfeld H, Gerber P, Wassenaar T, Castel V, Rosales M, de Haan C|date=2006|publisher=Food and Agriculture Organization of the UN|isbn=978-92-5-105571-7|archive-url=https://web.archive.org/web/20080625012113/http://www.virtualcentre.org/en/library/key_pub/longshad/A0701E00.pdf|archive-date=25 June 2008}}</ref> according to the [[Intergovernmental Panel on Climate Change]], the three main causes of the increase in greenhouse gases observed over the past 250 years have been fossil fuels, land use, and agriculture.<ref>[http://ipcc-wg1.ucar.edu/wg1/wg1-report.html Intergovernmental Panel on Climate Change] {{webarchive|url=https://web.archive.org/web/20070501031449/http://ipcc-wg1.ucar.edu/wg1/wg1-report.html|date=1 May 2007}} ([[Intergovernmental Panel on Climate Change|IPCC]])</ref>
 
The agricultural food system is responsible for a significant amount of greenhouse gas emissions.<ref>{{cite web|date=2011|title=The Food Gap: The Impacts of Climate Change on Food Production: a 2020 Perspective|url=http://www.feu-us.org/images/The_Food_Gap.pdf|url-status=dead|archive-url=https://web.archive.org/web/20120416214231/http://www.feu-us.org/images/The_Food_Gap.pdf|archive-date=16 April 2012}}</ref><ref name="strategies">{{Cite journal|last1=Friel|first1=Sharon|last2=Dangour|first2=Alan D.|last3=Garnett|first3=Tara|last4=Lock|first4=Karen|last5=Chalabi|first5=Zaid|last6=Roberts|first6=Ian|last7=Butler|first7=Ainslie|last8=Butler|first8=Colin D.|last9=Waage|first9=Jeff|last10=McMichael|first10=Anthony J.|last11=Haines|first11=Andy|display-authors=3|year=2009|title=Public health benefits of strategies to reduce greenhouse-gas emissions: food and agriculture|journal=The Lancet|volume=374|issue=9706|pages=2016–2025|doi=10.1016/S0140-6736(09)61753-0|pmid=19942280|s2cid=6318195}}</ref>
 
According to the [[IPCC]], it makes up at least 10-12% of emissions, and when there are changes in land due to the agriculture, it can rise as high as 17%. Emissions from farms of [[nitrous oxide]], [[methane]] and [[carbon dioxide]] are the main culprits; being up to half of the greenhouse-gases produced by the overall food industry, or 80% of agricultural emissions.<ref name="strategies" />
 
The types of farm animals can be put into two categories: [[monogastric]] and [[ruminant]]. Typically, beef and dairy, in other words, ruminant products, rank high in greenhouse-gas emissions; monogastric, or pigs and poultry-related foods, are low. The consumption of the monogastric types, therefore, yield less emissions. This is due to the fact that these types of animals have a higher feed-conversion efficiency, and also do not produce any methane.<ref name="strategies" />
 
There are many strategies that can be used to help soften the effects, and the further production of greenhouse gas emissions. Some of these strategies include a higher efficiency in livestock farming, which includes management, as well as technology; a more effective process of managing manure; a lower dependence upon fossil-fuels and nonrenewable resources; a variation in the animals' eating and drinking duration, time and location; and a cutback in both the production and consumption of animal-sourced foods.<ref name="strategies" /><ref name="impact">{{Cite journal|last1=Thornton|first1=P.K.|last2=van de Steeg|first2=J.|last3=Notenbaert|first3=A.|last4=Herrero|first4=M.|year=2009|title=The impacts of climate change on livestock and livestock systems in developing countries: A review of what we know and what we need to know|journal=Agricultural Systems|volume=101|issue=3|pages=113–127|doi=10.1016/j.agsy.2009.05.002}}</ref><ref>{{cite report|url=http://www.uoguelph.ca/~c-ciarn/documents/World_Bank_Paper.pdf|title=Climate Change and Agriculture: A Review of Impacts and Adaptions|last1=Kurukulasuriya|first1=Pradeep|last2=Rosenthal|first2=Shane|date=June 2003|publisher=[[World Bank]]}}</ref><ref name="who">{{cite report|url=https://www.who.int/globalchange/publications/climchange.pdf|title=Climate Change and Human Health: Risks and Responses|last1=McMichael|first1=A.J.|last2=Campbell-Lendrum|first2=D.H.|date=2003|publisher=World Health Organization|isbn=92-4-156248-X|last3=Corvalán|first3=C.F.|last4=Ebi|first4=K.L.|last5=Githeko|first5=A.K.|last6=Scheraga|first6=J.D.|last7=Woodward|first7=A.|display-authors=3}}</ref>
 
===Land use===
 
Agriculture contributes to greenhouse gas increases through land use in four main ways:
* CO<sub>2</sub> releases linked to [[deforestation]]
* Methane releases from [[rice|rice cultivation]]
* Methane releases from [[enteric fermentation]] in cattle
* [[Nitrous oxide]] releases from [[fertilizer]] application
 
Together, these agricultural processes comprise 54% of [[methane emissions]], roughly 80% of nitrous oxide emissions, and virtually all carbon dioxide emissions tied to land use.<ref>[http://www.grida.no/climate/ipcc/emission/076.htm Intergovernmental Panel on Climate Change Special Report on Emissions Scenarios] retrieved 26 June 2007</ref>
 
The planet's major changes to [[land cover]] since 1750 have resulted from [[deforestation]] in [[temperate region]]s: when forests and woodlands are cleared to make room for fields and [[pasture]]s, the [[albedo]] of the affected area increases, which can result in either warming or cooling effects, depending on local conditions.<ref>{{cite web|title=Intergovernmental Panel on Climate Change|url=http://www.ipcc.ch/pdf/assessment-report/ar4/wg1/ar4-wg1-chapter2.pdf}}</ref> Deforestation also affects regional [[RuBisCO|carbon reuptake]], which can result in increased concentrations of [[carbon dioxide|CO<sub>2</sub>]], the dominant greenhouse gas.<ref>[http://www.ipcc.ch/pdf/assessment-report/ar4/wg1/ar4-wg1-ts.pdf IPCC Technical Summary] retrieved 25 June 2007</ref> Land-clearing methods such as [[slash and burn]] compound these effects by burning [[biomatter]], which directly releases greenhouse gases and particulate matter such as [[soot]] into the air.
 
=== Livestock ===
 
Livestock and livestock-related activities such as deforestation and increasingly fuel-intensive farming practices are responsible for over 18%<ref name="lls">{{Cite book|last1=Steinfeld|first1=Henning|url=https://books.google.com/books?id=1B9LQQkm_qMC|title=Livestock's Long Shadow: Environmental Issues and Options|last2=Gerber|first2=Pierre|last3=Wassenaar|first3=T. D.|last4=Castel|first4=Vincent|last5=de Haan|first5=Cees|date=1 January 2006|publisher=Food & Agriculture Org.|isbn=9789251055717|archive-url=https://web.archive.org/web/20080625012113/http://www.virtualcentre.org/en/library/key_pub/longshad/A0701E00.pdf|archive-date=25 June 2008|url-status=dead|via=Google Books|name-list-style=vanc}},</ref> of human-made greenhouse gas emissions, including:
* 9% of global [[carbon dioxide]] emissions
* 35–40% of global [[methane]] emissions (chiefly due to [[enteric fermentation]] and [[manure]])
* 64% of global nitrous oxide emissions (chiefly due to [[fertilizer]] use.<ref name="lls" />)
[[File:Livestock market in Mali.jpg|thumb]]
Livestock activities also contribute disproportionately to land-use effects, since crops such as [[Maize|corn]] and [[alfalfa]] are cultivated in order to feed the animals.
 
In 2010, [[enteric fermentation]] accounted for 43% of the total greenhouse gas emissions from all agricultural activity in the world.<ref>Food and Agriculture Organization of the United Nations (2013) [http://www.fao.org/docrep/018/i3107e/i3107e00.htm "FAO STATISTICAL YEARBOOK 2013 World Food and Agriculture"]. See data in Table 49.</ref> The meat from ruminants has a higher carbon equivalent footprint than other meats or vegetarian sources of protein based on a global meta-analysis of lifecycle assessment studies.<ref>{{cite journal|last1=Ripple|first1=William J.|last2=Smith|first2=Pete|last3=Haberl|first3=Helmut|last4=Montzka|first4=Stephen A.|last5=McAlpine|first5=Clive|last6=Boucher|first6=Douglas H.|date=20 December 2013|title=Ruminants, climate change and climate policy|journal=Nature Climate Change|volume=4|issue=1|pages=2–5|bibcode=2014NatCC...4....2R|doi=10.1038/nclimate2081|name-list-style=vanc}}</ref> Methane production by animals, principally ruminants, is estimated 15-20% global production of methane.<ref>{{cite journal|author2-link=Ronald Oremland|vauthors=Cicerone RJ, Oremland RS|date=December 1988|title=Biogeochemical aspects of atmospheric methane.|url=http://www.escholarship.org/uc/item/3xq3t703|journal=Global Biogeochemical Cycles|volume=2|issue=4|pages=299–327|bibcode=1988GBioC...2..299C|doi=10.1029/GB002i004p00299}}</ref><ref>{{cite journal|vauthors=Yavitt JB|date=1992|title=Methane, biogeochemical cycle.|journal=Encyclopedia of Earth System Science|location=London, England|publisher=Academic Press|volume=3|pages=197–207}}</ref>
 
Worldwide, livestock production occupies 70% of all land used for agriculture, or 30% of the land surface of the Earth.<ref name="lls" /> The way livestock is grazed also decides the fertility of the land in the future, not circulating grazing can lead to unhealthy soil and the [[agricultural expansion|expansion]] of livestock farms affects the habitats of local animals and has led to the drop in population of many local species from being displaced.
 
===Fertilizer production===
{{Excerpt|Fertilizer|Contribution to climate change}}
 
===Soil erosion===
[[File:Occurrences_of_Soil_erosion.jpg|thumb]]
Large scale farming can cause large amounts of soil erosion, causing between 25 and 40 percent of soil to reach water sources, with it carrying the pesticides and fertilizers used by farmers, thus polluting bodies of water further.<ref>{{cite journal|vauthors=Ruhl, JB|date=2000|title=Farms, Their Environmental Harms, and Environmental Law.|url=https://www.jstor.org/stable/24113926|journal=Ecology Law Quarterly|volume=27|issue=2|pages=263–349|jstor=24113926}}</ref> The trend to constantly bigger farms has been highest in [[United States]] and [[Europe]], due to financial arrangements, contract farming. Bigger farms tend to favour monocultures, overuse water resources, accelerate the [[deforestation]] and a decline in [[soil quality]]. A study from 2020 by the [[International Land Coalition]], together with [[Oxfam]] and World Inequality Lab found that 1% of the land owners manage 70% of the world's farmland. The highest discrepance can be found in [[Latin America]]: The poorest 50% own just 1% of the land. Small landowners, as individuals or families, tend to be more cautious in land use. As of 2020, however, the proportion of small landowners has been decreasing since the 1980s. Currently, the largest share of smallholdings can be found in [[Asia]] and [[Africa]].<ref>{{Cite web|date=24 November 2020|title=1% of farms operate 70% of world's farmland|url=http://www.theguardian.com/environment/2020/nov/24/farmland-inequality-is-rising-around-the-world-finds-report|access-date=25 November 2020|website=the Guardian|language=en}}</ref>
 
== Impact of climate change on agriculture ==
[[File:Net crops tropicalvsworld.png|thumb|upright=1.5|Graph of net crop production worldwide and in selected tropical countries. Raw data from the United Nations.<ref name="fao.org">{{Cite web|url=http://www.fao.org/faostat/en/|title=FAOSTAT|website=www.fao.org}}</ref>]]
[[File:Corn and soybean temperature response (ARS USDA).png|thumb|upright=2|right|alt=refer to caption and image description|For each plant variety, there is an optimal temperature for vegetative growth, with growth dropping off as temperatures increase or decrease. Similarly, there is a range of temperatures at which a plant will produce seed. Outside of this range, the plant will not reproduce. As the graphs show, [[maize]] will fail to reproduce at temperatures above 95&nbsp;°F (35&nbsp;°C) and [[soybean]] above 102&nbsp;°F (38.8&nbsp;°C).<ref>{{Include-USGov
| agency=US Global Change Research Program ([[USGCRP]])
| source={{cite web |title=Corn and Soybean Temperature Response |url=http://nca2009.globalchange.gov/corn-and-soybean-temperature-response |access-date=30 May 2013 |url-status=dead |archive-url=https://web.archive.org/web/20130512133320/http://nca2009.globalchange.gov/corn-and-soybean-temperature-response |archive-date=12 May 2013}}, in: {{citation
|year = 2017
|title = Global Climate Change Impacts in the United States
|editor = Karl, T.R.
|publisher = Cambridge University Press
|isbn = 978-0-521-14407-0
|url = http://nca2009.globalchange.gov/
|display-editors = etal
}}
}}
</ref>]]
Despite technological advances, such as [[crop breeding|improved varieties]], [[GMO|genetically modified organisms]], and [[irrigation]] systems, climate is still a key factor in agricultural productivity, as well as [[soil]] properties and [[Biota (ecology)|natural communities]]. The effect of climate on agriculture is related to variabilities in local climates rather than in global climate patterns. Consequently, in making an assessment, [[agronomist]]s must consider each [[ecoregion|local area]].
 
Since the formation of the [[World Trade Organization]] in 1995, global agricultural trade has increased. 'Global agricultural exports have more than tripled in value and more than doubled in volume since 1995, exceeding US $1.8 trillion in 2018'.<ref>{{Cite web|date=29 July 2020|title=The current state of agricultural trade and the World Trade Organization|url=https://www.ifpri.org/news-release/current-state-agricultural-trade-and-world-trade-organization|website=International Food Policy Research Institute}}</ref> [[agricultural economics|Agricultural trade]] provides significant amounts of food for major importing countries, and is a source of [[gross domestic product|income]] for exporting countries. The international aspect of trade and security in terms of food implies the need to also consider the [[effects of global warming|effects of climate change]] on a global scale.
 
The [[Intergovernmental Panel on Climate Change]] (IPCC) has produced several reports that have assessed the [[scientific literature]] on climate change. The [[IPCC Third Assessment Report]], published in 2001, concluded that the poorest countries would be hardest hit, with reductions in crop yields in most tropical and sub-tropical regions due to decreased water availability, and new or changed insect pest incidence. In Africa and Latin America many rainfed crops are near their maximum temperature tolerance, so that yields are likely to fall sharply for even small climate changes; falls in agricultural productivity of up to 30% over the 21st century are projected. Marine life and the [[Fisheries and climate change|fishing industry]] will also be severely affected in some places.
 
In the report published in 2014 the [[Intergovernmental Panel on Climate Change]] says that the world may reach "a threshold of global warming beyond which current agricultural practices can no longer support large human civilizations." by the middle of the 21st century. In 2019 it published reports in which it says that millions already suffer from food insecurity due to climate change and predicted decline in global crop production of 2% - 6% by decade.<ref>{{cite web |last1=Smith |first1=K.R. |last2=Woodward |first2=A. |last3=Campbell-Lendrum |first3=D. |last4=Chadee |first4=D.D. |last5=Honda |first5=Y. |last6=Liu |first6=Q. |last7=Olwoch |first7=J.M. |last8=Revich |first8=B. |last9=Sauerborn |first9=R. |title=Climate Change 2014: Impacts, Adaptation, and Vulnerability. Part A: Global and Sectoral Aspects. Contribution of Working Group II to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. Chapter11: : Human health: impacts, adaptation, and co-benefits. Section: 11.8.2 (Limits to Food Production and Human Nutrition). Page 736. |url=https://www.ipcc.ch/site/assets/uploads/2018/02/WGIIAR5-Chap11_FINAL.pdf |website=Intergovernmental Panel on Climate Change |publisher=Intergovernmental Panel on Climate Change |access-date=29 October 2019}}</ref><ref>{{cite news |last1=Little |first1=Amanda |title=Climate Change Is Likely to Devastate the Global Food Supply. But There's Still Reason to Be Hopeful |url=https://time.com/5663621/climate-change-food-supply/ |access-date=30 August 2019 |agency=Time |date=28 August 2019}}</ref> A 2021 study estimates that the severity of heatwave and drought impacts on crop production tripled over the last 50 years in Europe – from losses of -2.2 during 1964-1990 to -7.3% in 1991-2015.<ref>{{cite news |title=Europe's heat and drought crop losses tripled in 50 years: study |url=https://phys.org/news/2021-04-europe-drought-crop-losses-tripled.html |access-date=19 April 2021 |work=phys.org |language=en}}</ref><ref>{{cite journal |last1=Brás |first1=Teresa Armada |last2=Seixas |first2=Júlia |last3=Carvalhais |first3=Nuno |last4=Jägermeyr |first4=Jonas |title=Severity of drought and heatwave crop losses tripled over the last five decades in Europe |journal=Environmental Research Letters |date=18 March 2021 |volume=16 |issue=6 |page=065012 |doi=10.1088/1748-9326/abf004 |bibcode=2021ERL....16f5012B |language=en |issn=1748-9326|doi-access=free }} [[File:CC-BY icon.svg|50px]] Available under [https://creativecommons.org/licenses/by/4.0/ CC BY 4.0].</ref>
 
Climate change can reduce yields by the amplification of [[rossby wave]]s. There is a possibility that the effects are already existing.<ref>{{cite news |last1=Rosane |first1=Olivia |title=Study Finds 'Underexplored Vulnerability in the Food System': Jet Stream-Fueled Global Heat Waves |url=https://www.ecowatch.com/food-system-climate-change-2641559399.html |access-date=11 December 2019 |agency=Ecowatch |date=10 December 2019}}</ref>
 
Climate change induced by increasing [[greenhouse gas]]es is likely to affect crops differently from region to region. For example, average crop yield is expected to drop down to 50% in Pakistan according to the [[Met Office]] scenario whereas corn production in Europe is expected to grow up to 25% in optimum [[hydrologic]] conditions.
 
More favorable effects on yield tend to depend to a large extent on realization of the potentially [[beneficial effects of global warming|beneficial effects of carbon dioxide on crop growth]] and increase of efficiency in [[water use]]. Decrease in potential yields is likely to be caused by shortening of the growing period, decrease in water availability and poor [[vernalization]].
 
In the long run, the climatic change could affect agriculture in several ways:
* ''productivity'', in terms of [[quantity]] and [[Quality (business)|quality]] of crops
* ''agricultural practices'', through changes of water use (irrigation) and agricultural inputs such as [[herbicide]]s, [[insecticide]]s and [[fertilizer]]s
* ''environmental effects'', in particular in relation of frequency and intensity of soil [[drainage]] (leading to nitrogen leaching), [[soil erosion]], reduction of [[biodiversity|crop diversity]]
* ''rural space'', through the loss and gain of cultivated lands, land [[speculation]], land renunciation, and hydraulic amenities.
* ''adaptation'', organisms may become more or less competitive, as well as humans may develop urgency to develop more competitive organisms, such as flood resistant or [[Crop tolerance to seawater|salt resistant]] varieties of rice.
 
They are large uncertainties to uncover, particularly because there is lack of information on many specific local regions, and include the uncertainties on magnitude of climate change, the effects of technological changes on productivity, global food demands, and the numerous possibilities of adaptation.
 
Most agronomists believe that agricultural production will be mostly affected by the severity and pace of climate change, not so much by gradual trends in climate. If change is gradual, there may be enough time for [[biota (ecology)|biota]] adjustment. Rapid climate change, however, could harm agriculture in many countries, especially those that are already suffering from rather poor soil and climate conditions, because there is less time for optimum [[natural selection]] and adaption.
 
But much remains unknown about exactly how [[climate change]] may affect farming and [[food security]], in part because the role of farmer behaviour is poorly captured by crop-climate models. For instance, Evan Fraser, a geographer at the [[University of Guelph]] in [[Ontario]] [[Canada]], has conducted a number of studies that show that the socio-economic context of farming may play a huge role in determining whether a [[drought]] has a major, or an insignificant impact on crop production.<ref>{{cite journal | last1 = Fraser | first1 = E | year = 2007a | title = Travelling in antique lands: Studying past famines to understand present vulnerabilities to climate change | journal = Climate Change | volume = 83 | issue = 4| pages = 495–514 | doi=10.1007/s10584-007-9240-9 | bibcode = 2007ClCh...83..495F| s2cid = 154404797 }}</ref><ref name="Simelton, E. 2009">{{cite journal | vauthors = Simelton E, Fraser E, Termansen M | year = 2009 | title = Typologies of crop-drought vulnerability: an empirical analysis of the socio-economic factors that influence the sensitivity and resilience to drought of three major food crops in China (1961–2001) | journal = Environmental Science & Policy | volume = 12 | issue = 4| pages = 438–452 | doi=10.1016/j.envsci.2008.11.005}}</ref> In some cases, it seems that even minor droughts have big impacts on food security (such as happened in [[Ethiopia]] in the early 1980s where a minor drought triggered a massive [[famine]]), versus cases where even relatively large weather-related problems were adapted to without much hardship.<ref>{{cite journal | vauthors = Fraser ED, Termansen M, Sun N, Guan D, Simelton E, Dodds P, Feng K, Yu Y | year = 2008 | title = Quantifying socio economic characteristics of drought sensitive regions: evidence from Chinese provincial agricultural data | journal = Comptes Rendus Geoscience | volume = 340 | issue = 9–10| pages = 679–688 | doi=10.1016/j.crte.2008.07.004| bibcode = 2008CRGeo.340..679F }}</ref> Evan Fraser combines socio-economic models along with climatic models to identify "vulnerability hotspots"<ref name="Simelton, E. 2009"/> One such study has identified [[Corn production in the United States|US maize (corn) production]] as particularly [[Climate change vulnerability|vulnerable to climate change]] because it is expected to be exposed to worse droughts, but it does not have the socio-economic conditions that suggest farmers will adapt to these changing conditions.<ref>{{cite journal | vauthors = Fraser ED, Simelton E, Termansen M, Gosling SN, South A | year = 2013 | title = 'Vulnerability hotspots': integrating socio-economic and hydrological models to identify where cereal production may decline due to climate change induced drought | journal = Agricultural and Forest Meteorology | volume = 170 | pages = 195–205 | doi=10.1016/j.agrformet.2012.04.008 | bibcode = 2013AgFM..170..195F}}</ref> Other studies rely instead on projections of key agro-meteorological or agro-climate indices, such as growing season length, plant heat stress, or start of field operations, identified by land management stakeholders and that provide useful information on mechanisms driving climate change impact on agriculture.<ref>{{cite journal | vauthors = Harding AE, Rivington M, Mineter MJ, Tett SF | year = 2015 | title = Agro-meteorological indices and climate model uncertainty over the UK | journal = Climatic Change | volume = 128 | issue =1 | pages = 113–126 | doi=10.1007/s10584-014-1296-8| bibcode = 2015ClCh..128..113H | doi-access = free }}</ref><ref>{{cite journal | vauthors =Monier E, Xu L, Snyder R | year = 2016 | title = Uncertainty in future agro-climate projections in the United States and benefits of greenhouse gas mitigation | journal = Environmental Research Letters | volume = 11 | issue = 5 | pages = 055001 | doi=10.1088/1748-9326/11/5/055001| bibcode = 2016ERL....11e5001M | doi-access = free }}</ref>
 
=== Pest insects ===
Global warming could lead to an increase in pest insect populations, harming yields of staple crops like [[wheat]], [[soybean]]s, and corn.<ref name="Live Science">{{Cite news|url=http://www.livescience.com/4296-global-warming-trigger-insect-population-boom.html|title=Global Warming Could Trigger Insect Population Boom|work=Live Science|access-date=2 May 2017}}</ref> While warmer temperatures create longer growing seasons, and faster growth rates for plants, it also increases the metabolic rate and number of breeding cycles of insect populations.<ref name="Live Science"/> Insects that previously had only two breeding cycles per year could gain an additional cycle if warm growing seasons extend, causing a population boom. Temperate places and higher [[latitude]]s are more likely to experience a dramatic change in insect populations.<ref>{{Cite journal|last=Stange|first=Erik| name-list-style = vanc |date=November 2010|title=Climate Change Impact: Insects|url=http://www.els.net/WileyCDA/ElsArticle/refId-a0022555.html|publisher=[[Norwegian Institute for Nature Research]]}}</ref>
 
The [[University of Illinois at Urbana–Champaign|University of Illinois]] conducted studies to measure the effect of warmer temperatures on soybean plant growth and Japanese beetle populations.<ref name="Union of Concerned Scientists">{{Cite news|url=http://www.ucsusa.org/global_warming/science_and_impacts/impacts/Global-warming-insects.html#.WOwzzDvy|title=Crops, Beetles, and Carbon Dioxide|work=Union of Concerned Scientists|access-date=2 May 2017|language=en}}</ref> Warmer temperatures and elevated CO<sub>2</sub> levels were simulated for one field of soybeans, while the other was left as a control. These studies found that the soybeans with elevated CO<sub>2</sub> levels grew much faster and had higher yields, but attracted [[Japanese beetle]]s at a significantly higher rate than the control field.<ref name="Union of Concerned Scientists"/> The beetles in the field with increased CO<sub>2</sub> also laid more eggs on the soybean plants and had longer lifespans, indicating the possibility of a rapidly expanding population. DeLucia projected that if the project were to continue, the field with elevated CO<sub>2</sub> levels would eventually show lower yields than that of the control field.<ref name="Union of Concerned Scientists"/>
 
The increased CO<sub>2</sub> levels deactivated three genes within the soybean plant that normally create chemical defences against pest insects. One of these defences is a protein that blocks digestion of the soy leaves in insects. Since this gene was deactivated, the beetles were able to digest a much higher amount of plant matter than the beetles in the control field. This led to the observed longer lifespans and higher egg-laying rates in the experimental field.<ref name="Union of Concerned Scientists"/>
[[File:Desert Locust swarm.jpg|thumb|Desert locust swarms linked to climate change]]
 
There are a few proposed solutions to the issue of expanding pest populations. One proposed solution is to increase the number of pesticides used on future crops.<ref name="agadapt.ucdavis.edu">{{Cite web|url=http://agadapt.ucdavis.edu/pestsdiseases/|title=Agricultural Adaptation to Climate Change|access-date=2 May 2017|archive-url=https://web.archive.org/web/20170504021853/http://agadapt.ucdavis.edu/pestsdiseases/|archive-date=4 May 2017|url-status=dead}}</ref> This has the benefit of being relatively cost effective and simple, but may be ineffective. Many pest insects have been building up an [[Pesticide resistance|immunity]] to these pesticides. Another proposed solution is to utilize [[Biological pest control|biological control agents]].<ref name="agadapt.ucdavis.edu" /> This includes things like planting rows of native vegetation in between rows of crops. This solution is beneficial in its overall environmental impact. Not only are more native plants getting planted, but pest insects are no longer building up an immunity to pesticides. However, planting additional native plants requires more room, which destroys additional acres of public land. The cost is also much higher than simply using pesticides.<ref>{{Cite journal|last=Stange|first=Erik| name-list-style = vanc |date=November 2010|title=Climate Change Impact: Insects|publisher=[[Norwegian Institute for Nature Research]]}}</ref>
 
Studies have shown that when {{CO2}} levels rise, [[soybean]] leaves are less nutritious; therefore plant-eating beetles have to eat more to get their required [[nutrients]].<ref name="Ferber & Epstein">{{cite book|last1=Epstein|first1=Paul R.|url=https://archive.org/details/unset0000unse_c1j4|title=Changing Planet, Changing Health: How the Climate Crisis Threatens Our Health and what We Can Do about it|last2=Ferber|first2=Dan|publisher=University of California Press|year=2011|isbn=978-0-520-26909-5|url-access=registration}}{{page needed|date=August 2016}}</ref> In addition, soybeans are less capable of defending themselves against the predatory insects under high {{CO2}}. The {{CO2}} diminishes the plant's [[jasmonic acid]] production, an insect-killing poison that is excreted when the plant senses it's being attacked. Without this protection, beetles are able to eat the soybean leaves freely, resulting in a lower crop yield.<ref name="Ferber & Epstein" /> This is not a problem unique to soybeans, and many plant species’ defense mechanisms are impaired in a high {{CO2}} environment.<ref name="Chakra" />
 
Currently, pathogens take 10-16% of the global harvest and this level is likely to rise as plants are at an ever-increasing risk of exposure to pests and pathogens.<ref name="Chakra" /> Historically, cold temperatures at night and in the winter months would kill off [[insects]], [[bacteria]] and [[fungi]]. The warmer, wetter winters are promoting fungal plant diseases like wheat rusts ([[stripe rust|stripe]] and [[wheat brown rust|brown/leaf]]) and [[soybean rust]] to travel northward.<ref name="Luck-et-al-2011" /> Soybean rust is a vicious plant pathogen that can kill off entire fields in a matter of days, devastating farmers and costing billions in agricultural losses. Another example is the [[Mountain Pine Beetle]] epidemic in [[BC, Canada]] which killed millions of pine trees because the winters were not cold enough to slow or kill the growing beetle larvae.<ref name="Ferber & Epstein" /> The increasing incidence of flooding and heavy rains also promotes the growth of various other plant pests and diseases.<ref name="Rod112">{{cite journal|last1=Rodenburg|first1=J.|last2=Meinke|first2=H.|last3=Johnson|first3=D. E.|date=August 2011|title=Challenges for weed management in African rice systems in a changing climate|url=http://ecite.utas.edu.au/69596|journal=[[The Journal of Agricultural Science]]|type=Submitted manuscript|volume=149|issue=4|pages=427–435|doi=10.1017/S0021859611000207|s2cid=5336023}}</ref> On the opposite end of the spectrum, drought conditions favour different kinds of pests like [[aphids]], [[whiteflies]] and [[locusts]].<ref name="Ferber & Epstein" />
 
The competitive balance between plants and pests has been relatively stable for the past century, but with the rapidly shifting climate, there is a change in this balance which often favours the more biologically diverse [[weed]]s over the [[Monocropping|monocrops]] most farms consist of.<ref name="Rod112" /> Currently, weeds claim about one tenth of global crop yields annually as there are about eight to ten weed species in a field competing with crops.<ref name="Ferber & Epstein" /> Characteristics of weeds such as their [[genetic diversity]], cross-breeding ability, and fast-growth rates put them at an advantage in changing climates as these characteristics allow them to adapt readily in comparison to most farm's uniform crops, and give them a biological advantage.<ref name="Ferber & Epstein" /> There is also a shift in the distribution of pests as the altered climate makes areas previously uninhabitable more uninviting.<ref name="Thomson">{{cite journal|last1=Thomson|first1=Linda J.|last2=Macfadyen|first2=Sarina|last3=Hoffmann|first3=Ary A.|date=March 2010|title=Predicting the effects of climate change on natural enemies of agricultural pests|journal=Biological Control|volume=52|issue=3|pages=296–306|doi=10.1016/j.biocontrol.2009.01.022}}</ref> Finally, with the increased {{CO2}} levels, [[herbicides]] will lose their efficiency which in turn increases the tolerance of weeds to herbicides.<ref name="Rod112" />
 
==== Locusts ====
When climate change leads to hotter weather, coupled with wetter conditions, this can result in more damaging [[locust]] swarms.<ref name=":7">{{Cite web|date=6 February 2020|title=Locust swarms and climate change|url=http://www.unenvironment.org/news-and-stories/story/locust-swarms-and-climate-change|access-date=29 November 2020|website=UN Environment|language=en}}</ref> This occurred for example in some East African nations in the beginning of 2020.<ref name=":7" />
 
==== Fall armyworms ====
The [[fall armyworm]], ''Spodoptera frugiperda'', is a highly invasive plant pest that has in the recent years spread to countries in Sub-Saharan African. The spread of this plant pest is linked to climate change as experts confirm that climate change is bringing more crop pests to Africa and it is expected that these highly invasive crop pests will spread to other parts of the planet since they have a high capacity to adapt to different environments. The fall armyworm can have massive damage to crops, especially [[maize]], which affects agricultural productivity.<ref>{{Cite journal|last=Zacarias|first=Daniel Augusta|date=1 August 2020|title=Global bioclimatic suitability for the fall armyworm, Spodoptera frugiperda (Lepidoptera: Noctuidae), and potential co-occurrence with major host crops under climate change scenarios|url=https://doi.org/10.1007/s10584-020-02722-5|journal=Climatic Change|language=en|volume=161|issue=4|pages=555–566|doi=10.1007/s10584-020-02722-5|bibcode=2020ClCh..161..555Z|s2cid=218573386|issn=1573-1480}}</ref>
 
=== Diseases and weeds ===
A very important point to consider is that weeds would undergo the same acceleration of cycle as cultivated crops, and would also benefit from carbonaceous fertilization. Since most weeds are C3 plants, they are likely to compete even more than now against C4 crops such as corn. However, on the other hand, some results make it possible to think that [[weedkiller]]s could increase in effectiveness with the temperature increase.<ref>{{cite web|title=Early Summer Weed Control|url=http://extension.unl.edu/statewide/sw3/6.17.15%20Early%20Summer%20Weed%20Control.pdf}}</ref>
 
Global warming would cause an increase in rainfall in some areas, which would lead to an increase of atmospheric humidity and the duration of the [[wet season]]s. Combined with higher temperatures, these could favour the development of [[fungi|fungal]] diseases.<ref name="Luck-et-al-2011" /> Similarly, because of higher temperatures and humidity, there could be an increased pressure from insects and [[Vector (epidemiology)|disease vectors]].<ref name="Luck-et-al-2011" />
 
Research has shown that climate change may alter the developmental stages of [[Plant pathology#Plant pathogens|plant pathogens]] that can affect crops.<ref name=":0">{{cite journal | vauthors = Coakley SM, Scherm H, Chakraborty S | title = Climate change and plant disease management | journal = Annual Review of Phytopathology | volume = 37 | pages = 399–426 | date = September 1999 | pmid = 11701829 | doi = 10.1146/annurev.phyto.37.1.399 }}</ref> Change in weather patterns and temperature due to climate change leads to dispersal of plant pathogens as hosts migrate to areas with more favourable conditions. This results to increased more crop losses due to diseases.<ref name=":0" /><ref name="Luck-et-al-2011" /> It has been predicted that the effect of climate change will add a level of complexity to figuring out how to maintain sustainable agriculture.<ref name=":0" /> Unless farmers and potato cultivars can adapt to the new environment, the worldwide potato yield will be 18-32% lower than currently.<ref name="Luck-et-al-2011" />
 
===Observed impacts===
Effects of regional climate change on agriculture have been limited.<ref name=rosen>{{cite book | vauthors = Rosenzweig C | contribution = Executive summary | title = Chapter 1: Assessment of Observed Changes and Responses in Natural and Managed Systems | series = Climate change 2007: impacts, adaptation and vulnerability: contribution of Working Group II to the fourth assessment report of the Intergovernmental Panel on Climate Change | publisher = Print version: CUP. This version: IPCC website | year = 2007 | location = Cambridge University Press (CUP): Cambridge, UK | isbn = 978-0-521-88010-7 | url = http://www.ipcc.ch/publications_and_data/ar4/wg2/en/ch1s1-es.html | veditors = Parry MC | access-date = 25 June 2011 | display-editors = etal | archive-url = https://web.archive.org/web/20181102223808/http://www.ipcc.ch/publications_and_data/ar4/wg2/en/ch1s1-es.html | archive-date = 2 November 2018 | url-status = dead }}</ref> Changes in crop [[phenology]] provide important evidence of the response to recent regional climate change.<ref>{{cite book | vauthors = Rosenzweig C | contribution = 1.3.6.1 Crops and livestock | title = Chapter 1: Assessment of Observed Changes and Responses in Natural and Managed Systems | series = Climate change 2007: impacts, adaptation and vulnerability: contribution of Working Group II to the fourth assessment report of the Intergovernmental Panel on Climate Change | url = http://www.ipcc.ch/publications_and_data/ar4/wg2/en/ch1s1-3-6-1.html | veditors = Parry ML | publisher = Print version: CUP. This version: IPCC website | year = 2007 | location = Cambridge University Press (CUP): Cambridge, UK | isbn = 978-0-521-88010-7 | access-date = 25 June 2011 | display-editors = etal | archive-url = https://web.archive.org/web/20181103092229/http://www.ipcc.ch/publications_and_data/ar4/wg2/en/ch1s1-3-6-1.html | archive-date = 3 November 2018 | url-status = dead }}</ref> Phenology is the study of natural phenomena that recur periodically, and how these phenomena relate to climate and seasonal changes.<ref>{{cite book | contribution = Definition of "phenology" | title = Appendix I: Glossary | series = Climate change 2007: impacts, adaptation and vulnerability: contribution of Working Group II to the fourth assessment report of the Intergovernmental Panel on Climate Change | url = http://www.ipcc.ch/publications_and_data/ar4/wg2/en/annexessglossary-p-z.html | veditors = Parry ML | publisher = Print version: CUP. This version: IPCC website | year = 2007 | location = Cambridge University Press (CUP): Cambridge, UK | isbn = 978-0-521-88010-7 | access-date = 25 June 2011 | display-editors = etal | archive-url = https://web.archive.org/web/20111108191024/http://www.ipcc.ch/publications_and_data/ar4/wg2/en/annexessglossary-p-z.html | archive-date = 8 November 2011 | url-status = dead }}</ref> A significant advance in phenology has been observed for agriculture and forestry in large parts of the Northern Hemisphere.<ref name=rosen/>
 
[[Drought]]s have been occurring more frequently because of global warming and they are expected to become more frequent and intense in Africa, southern Europe, the Middle East, most of the Americas, Australia, and Southeast Asia.<ref>{{Cite journal | last1 = Dai | first1 = A. | doi = 10.1002/wcc.81 | title = Drought under global warming: A review | journal = Wiley Interdisciplinary Reviews: Climate Change | volume = 2 | pages = 45–65 | year = 2011 | url = https://zenodo.org/record/1229380 | bibcode = 2011AGUFM.H42G..01D }}</ref> Their impacts are aggravated because of increased water demand, [[population growth]], [[urban expansion]], and environmental protection efforts in many areas.<ref>{{Cite journal | vauthors = Mishra AK, Singh VP | doi = 10.1016/j.jhydrol.2011.03.049 | title = Drought modeling – A review | journal = Journal of Hydrology | volume = 403 | issue = 1–2 | pages = 157–175 | year = 2011 | bibcode = 2011JHyd..403..157M }}</ref> Droughts result in crop failures and the loss of pasture grazing land for livestock.<ref>{{Cite journal | vauthors = Ding Y, Hayes MJ, Widhalm M | doi = 10.1108/09653561111161752 | title = Measuring economic impacts of drought: A review and discussion | journal = Disaster Prevention and Management | volume = 20 | issue = 4 | pages = 434–446 | year = 2011 | url = http://digitalcommons.unl.edu/natrespapers/196 }}</ref> Some farmers may choose to permanently stop farming a drought-affected area and go elsewhere.<ref>{{Cite news|last=Gale|first=Jordan|last2=Olmos|first2=Sergio|date=4 September 2021|title=When Hard Jobs Turn Hazardous|language=en-US|work=The New York Times|url=https://www.nytimes.com/2021/09/04/business/economy/when-hard-jobs-turn-hazardous.html|access-date=4 September 2021|issn=0362-4331}}</ref>
 
Most observed impacts:
 
* Shifting in precipitation patterns; longer periods of both heavy rain and dryness.
* Increase in temperature average levels; hotter summers and warmer winters can affect plants cycles, and lead to early blooming,<ref>{{Cite journal|last=Wolfe|first=David W.|last2=Schwartz|first2=Mark D.|last3=Lakso|first3=Alan N.|last4=Otsuki|first4=Yuka|last5=Pool|first5=Robert M.|last6=Shaulis|first6=Nelson J.|date=2004|title=Climate change and shifts in spring phenology of three horticultural woody perennials in northeastern USA|url=http://dx.doi.org/10.1007/s00484-004-0248-9|journal=International Journal of Biometeorology|volume=49|issue=5|pages=303–309|doi=10.1007/s00484-004-0248-9|issn=0020-7128}}</ref><ref>{{Cite journal|last=Grab|first=Stefan|last2=Craparo|first2=Alessandro|date=2011|title=Advance of apple and pear tree full bloom dates in response to climate change in the southwestern Cape, South Africa: 1973–2009|url=https://linkinghub.elsevier.com/retrieve/pii/S0168192310002893|journal=Agricultural and Forest Meteorology|language=en|volume=151|issue=3|pages=406–413|doi=10.1016/j.agrformet.2010.11.001}}</ref><ref>{{Cite journal|last=Martin|first=Phillip L.|last2=Krawczyk|first2=Teresa|last3=Khodadadi|first3=Fatemeh|last4=Aćimović|first4=Srđan G.|last5=Peter|first5=Kari A.|date=2021|title=Bitter Rot of Apple in the Mid-Atlantic United States: Causal Species and Evaluation of the Impacts of Regional Weather Patterns and Cultivar Susceptibility|url=http://dx.doi.org/10.1094/phyto-09-20-0432-r|journal=Phytopathology|pages=PHYTO–09-20-043|doi=10.1094/phyto-09-20-0432-r|issn=0031-949X}}</ref> lesser pollination, and frost damage.
* Increase in flooding; causes crop damaging, water pollution, soil erosion.
* Increase in drought levels; affects plants survival and increase the risk of wildfires.
* Degraded soils; monoculture cropping systems turns soil into less organic rich environment, and more prone to erosion and water pollution.
* Crop factories; industrial agriculture lacks biodiversity, which affects plants viability.
* Heavy fertilizers and pesticides; cause water pollution, exposure to chemicals and higher costs for farmers.<ref>{{Cite web|title=Climate Change and Agriculture {{!}} Union of Concerned Scientists|url=https://www.ucsusa.org/resources/climate-change-and-agriculture|access-date=30 November 2020|website=www.ucsusa.org|language=en}}</ref>
 
==== Examples ====
[[File:Banana farm Chinawal.jpg|thumb|upright|Banana farm at [[Chinawal]] village in [[Jalgaon district|Jalgaon district, India]]]]
In the summer of 2018, heat waves probably linked to climate change cause much lower than average yield in many parts of the world, especially in Europe. Depending on conditions during August, more crop failures could rise global [[food prices]].<ref name="This Summer's Heat Waves Could Be the Strongest Climate Signal Yet">{{cite news |last1=BERWYN |first1=BOB |title=This Summer's Heat Waves Could Be the Strongest Climate Signal Yet |url=https://insideclimatenews.org/news/27072018/summer-2018-heat-wave-wildfires-climate-change-evidence-crops-flooding-deaths-records-broken |access-date=9 August 2018 |agency=Inside Climate News |issue=Climate change |date=28 July 1018}}</ref> losses are compared to those of 1945, the worst harvest in memory. 2018 was the third time in four years that global wheat, rice and maize production failed to meet demand, forcing governments and food companies to release stocks from storage.
 
According to the UN report [[Special Report on Climate Change and Land|"Climate Change and Land: an IPCC special report on climate change, desertification, land degradation, sustainable land management, food security, and greenhouse gas fluxes in terrestrial ecosystems"]],<ref>{{Cite web|url=https://www.ipcc.ch/srccl/|title=Special Report on Climate Change and Land — IPCC site}}</ref><ref>{{Cite news|url=https://www.nytimes.com/2019/08/08/climate/climate-change-food-supply.html|title=Climate Change Threatens the World's Food Supply, United Nations Warns|first=Christopher|last=Flavelle|newspaper=The New York Times|date=8 August 2019}}</ref> food prices will rise by 80% by 2050 which will likely lead to food shortages. Some authors also suggest that the food shortages will probably affect poorer parts of the world far more than richer ones.
 
To prevent hunger, instability, new waves of [[climate refugee]]s, international help will be needed to countries who will miss the money to buy enough food and for also for stopping conflicts.<ref name="Heatwave devastates Europe's crops">{{cite news |last1=Vidal |first1=John |last2=Stewart |first2=Heather | name-list-style = vanc |title=Heatwave devastates Europe's crops |url= https://www.theguardian.com/guardianweekly/story/0,12674,1039838,00.html |access-date=9 August 2018 |agency=The Guardian |issue=Climate Change}}</ref><ref name="Conference Fortieth Session">{{cite web |last1=Graziano da Silva |first1=FAO Director-General José |title=Conference Fortieth Session |url=http://www.fao.org/about/who-we-are/director-gen/faodg-statements/detail/en/c/902584/ |website=Food and Agriculture Organization of the United Nations |access-date=9 August 2018}}</ref>(see also [[Climate change adaptation]]).
 
At the beginning of the 21 century, floods probably linked to climate change shortened the planting season in the Midwest region in [[United States]], causing damage to the agriculture sector. In May 2019 the floods reduced the projected [[maize|corn]] yield from 15 billion bushels to 14.2.<ref>{{cite news |last1=Higgins |first1=Eoin |title=Climate Crisis Brings Historic Delay to Planting Season, Pressuring Farmers and Food Prices |url=https://www.ecowatch.com/climate-crisis-farmers-planting-season-2638398287.html |access-date=30 May 2019 |agency=Ecowatch |date=29 May 2019}}</ref>
 
==== Early blooms ====
As a result of global warming, flowering times have come earlier, and early blooms can threaten the agriculture field because it threatens the plants survival and reproduction. Early flowering increases the risk of frost damage in some plant species and lead to ‘mismatches’ between plant flowering and pollinators interaction. "Around 70% of the world's most produced crop species rely to some extent on insect pollination, contributing an estimated €153 billion to the global economy and accounting for approximately 9% of agricultural production".<ref>{{Cite web|title=ECPA|url=https://www.ecpa.eu/|access-date=28 November 2020|website=www.ecpa.eu}}</ref> In addition to that, warmer temperatures in winter trigger many flowering plants to blossom, because plants need stimulation to flower, which is normally a long winter chill. And if a plant doesn't flower it can't reproduce. "But if winters keep getting milder, plants may not get cold enough to realize the difference when warmer springtime temperatures start" noted Syndonia Bret-Harte, a plant ecologist at the [[University of Alaska, Fairbanks]].<ref>{{Cite web|date=17 January 2013|title=Earliest Blooms Recorded in U.S. Due to Global Warming|url=https://www.nationalgeographic.com/news/2013/1/130116-spring-earlier-global-warming-plants-trees-blooming-science/|access-date=28 November 2020|website=National Geographic News|language=en}}</ref>
 
==== Effect on growing period ====
 
Duration of crop [[cell growth|growth]] [[biological life cycle|cycles]] are above all, related to temperature. An increase in temperature will speed up development.<ref>{{Cite book|last=Haldar|first=Ishita|url=https://books.google.com/books?id=2qR8Jdrd4EQC&q=Duration+of+crop+growth+cycles+are+above+all,+related+to+temperature.+An+increase+in+temperature+will+speed+up+development.&pg=PT33|title=Global Warming: The Causes and Consequences|date=23 December 2010|publisher=Mind Melodies|isbn=9789380302812|language=en|name-list-style=vanc}}</ref> In the case of an annual crop, the duration between [[sowing]] and [[harvesting]] will shorten (for example, the duration in order to harvest corn could shorten between one and four weeks). The shortening of such a cycle could have an adverse effect on productivity because [[senescence]] would occur sooner.<ref>{{Cite book|last=Bhattacharya|first=Amitav|url=https://books.google.com/books?id=94qdDwAAQBAJ&q=The+shortening+of+such+a+cycle+could+have+an+adverse+effect+on+productivity+because+senescence+would+occur&pg=PA119|title=Effect of High Temperature on Crop Productivity and Metabolism of Macro Molecules|date=14 June 2019|publisher=Academic Press|isbn=9780128176054|language=en|name-list-style=vanc}}</ref>
 
==== Effect of elevated carbon dioxide on crops ====
Elevated atmospheric carbon dioxide affects plants in a variety of ways. Elevated [[Carbon dioxide|CO<sub>2</sub>]] increases crop yields and growth through an increase in photosynthetic rate, and it also decreases water loss as a result of stomatal closing.<ref>{{Cite news|last=Hille|first=Karl|date=3 May 2016|title=Rising Carbon Dioxide Levels Will Help and Hurt Crops|language=en|work=NASA|url=https://www.nasa.gov/feature/goddard/2016/nasa-study-rising-carbon-dioxide-levels-will-help-and-hurt-crops|access-date=29 November 2018|name-list-style=vanc}}</ref> It limits the [[vaporization]] of water reaching the stem of the plant. [[Crassulacean acid metabolism|"Crassulacean Acid Metabolism"]] oxygen is all along the layer of the leaves for each plant leaves taking in CO<sub>2</sub>and release O<sub>2</sub>. The growth response is greatest in [[C3 carbon fixation|C<sub>3</sub> plants]], [[C4 carbon fixation|C<sub>4</sub> plants]], are also enhanced but to a lesser extent, and [[Crassulacean acid metabolism|CAM Plants]] are the least enhanced species.<ref>{{Cite journal|vauthors=Jongen M, Jones MB|date=1998|title=Effects of Elevated Carbon Dioxide on Plant Biomass Production and Competition in a Simulated Neutral Grassland Community|journal=Annals of Botany|volume=82|issue=1|pages=111–123|doi=10.1006/anbo.1998.0654|jstor=42765089|doi-access=free}}</ref> The stoma in these "CAM plant" stores remain shut all day to reduce exposure. rapidly rising levels of carbon dioxide in the atmosphere affect plants' absorption of nitrogen, which is the nutrient that restricts crop growth in most terrestrial ecosystems. Today's concentration of 400 ppm plants are relatively starved for nutrition. The optimum level of {{CO2}} for plant growth is about 5 times higher. Increased mass of {{CO2}} increases [[photosynthesis]], this {{CO2}} potentially stunts the growth of the plant. It limits the [[Reduction potential|reduction]] that crops lose through [[transpiration]].
 
Increase in global temperatures will cause an increase in evaporation rates and annual evaporation levels. Increased evaporation will lead to an increase in storms in some areas, while leading to accelerated drying of other areas. These storm impacted areas will likely experience increased levels of precipitation and increased flood risks, while areas outside of the storm track will experience less precipitation and increased risk of droughts.<ref>{{Cite web|title=How does climate change affect precipitation? {{!}} Precipitation Measurement Missions|url=https://pmm.nasa.gov/resources/faq/how-does-climate-change-affect-precipitation|access-date=29 November 2018|website=pmm.nasa.gov|language=en}}</ref> Water stress affects plant development and quality in a variety of ways first off drought can cause poor germination and impaired seedling development in plants.<ref>{{cite journal|vauthors=Farooq M, Wahid A, Kobayashi N, Fujita D, Basra SM|date=March 2009|title=Plant drought stress: effects, mechanisms and management|url=https://www.agronomy-journal.org/articles/agro/abs/2009/01/a7175/a7175.html|journal=Agronomy for Sustainable Development|language=en|volume=29|issue=1|pages=185–212|doi=10.1051/agro:2008021|s2cid=12066792}}</ref> At the same time plant growth relies on cellular division, cell enlargement, and differentiation. Drought stress impairs mitosis and cell elongation via loss of [[turgor pressure]] which results in poor growth.<ref name=":1">{{cite journal|display-authors=6|vauthors=Fahad S, Bajwa AA, Nazir U, Anjum SA, Farooq A, Zohaib A, Sadia S, Nasim W, Adkins S, Saud S, Ihsan MZ, Alharby H, Wu C, Wang D, Huang J|date=29 June 2017|title=Crop Production under Drought and Heat Stress: Plant Responses and Management Options|journal=Frontiers in Plant Science|volume=8|pages=1147|doi=10.3389/fpls.2017.01147|pmc=5489704|pmid=28706531|doi-access=free}}</ref> Development of leaves is also dependent upon turgor pressure, concentration of nutrients, and carbon assimilates all of which are reduced by drought conditions, thus drought stress lead to a decrease in leaf size and number.<ref name=":1" /> Plant height, biomass, leaf size and stem girth has been shown to decrease in Maize under water limiting conditions.<ref name=":1" /> Crop yield is also negatively effected by drought stress, the reduction in crop yield results from a decrease in photosynthetic rate, changes in leaf development, and altered allocation of resources all due to drought stress.<ref name=":1" /> Crop plants exposed to drought stress suffer from reductions in leaf water potential and transpiration rate, however [[water-use efficiency]] has been shown to increase in some crop plants such as wheat while decreasing in others such as potatoes.<ref>{{cite journal|display-authors=6|vauthors=Kahiluoto H, Kaseva J, Balek J, Olesen JE, Ruiz-Ramos M, Gobin A, Kersebaum KC, Takáč J, Ruget F, Ferrise R, Bezak P, Capellades G, Dibari C, Mäkinen H, Nendel C, Ventrella D, Rodríguez A, Bindi M, Trnka M|date=January 2019|title=Decline in climate resilience of European wheat|journal=Proceedings of the National Academy of Sciences of the United States of America|volume=116|issue=1|pages=123–128|doi=10.1073/pnas.1804387115|pmc=6320549|pmid=30584094|doi-access=free}}</ref><ref>{{cite journal|vauthors=Abbate PE, Dardanelli JL, Cantarero MG, Maturano M, Melchiori RJ, Suero EE|date=2004|title=Climatic and Water Availability Effects on Water-Use Efficiency in Wheat|journal=Crop Science|volume=44|issue=2|pages=474–483|doi=10.2135/cropsci2004.4740}}</ref><ref name=":1" /> Plants need water for the uptake of nutrients from the soil, and for the transport of nutrients throughout the plant, drought conditions limit these functions leading to stunted growth. Drought stress also causes a decrease in photosynthetic activity in plants due to the reduction of photosynthetic tissues, stomatal closure, and reduced performance of photosynthetic machinery. This reduction in photosynthetic activity contributes to the reduction in plant growth and yields.<ref name=":1" /> Another factor influencing reduced plant growth and yields include the allocation of resources; following drought stress plants will allocate more resources to roots to aid in water uptake increasing root growth and reducing the growth of other plant parts while decreasing yields.<ref name=":1" />
 
==== Effect on quality ====
According to the IPCC's TAR, "The importance of climate change impacts on grain and forage quality emerges from new research. Climate change can alter the adequacy ratios for specific macronutrients, carbohydrates and protein.<ref>{{Cite journal|last=Leisner|first=Courtney P.|date=2020-04-01|title=Review: Climate change impacts on food security- focus on perennial cropping systems and nutritional value|journal=Plant Science|language=en|volume=293|pages=110412|doi=10.1016/j.plantsci.2020.110412|issn=0168-9452|pmid=32081261|doi-access=free}}</ref> For rice, the amylose content of the grain—a major determinant of cooking quality—is increased under elevated CO<sub>2</sub>" (Conroy et al., 1994). Cooked rice grain from plants grown in high-{{CO2}} environments would be firmer than that from today's plants. However, concentrations of iron and zinc, which are important for human nutrition, would be lower (Seneweera and Conroy, 1997). Moreover, the protein content of the grain decreases under combined increases of temperature and CO<sub>2</sub> (Ziska et al., 1997).<ref>[http://www.grida.no/climate/ipcc_tar/wg2/208.htm "Climate Change 2001: Working Group II: Impacts, Adaptation and Vulnerability"] {{webarchive|url=https://web.archive.org/web/20090805194046/http://www.grida.no/climate/ipcc_tar/wg2/208.htm|date=5 August 2009}} IPCC</ref> Studies using [[Free-Air Concentration Enrichment|FACE]] have shown that increases in CO<sub>2</sub> lead to decreased concentrations of micronutrients in crop and non-crop plants with negative consequences for human nutrition,<ref>{{cite journal|vauthors=Loladze I|year=2002|title=Rising atmospheric CO2 and human nutrition: toward globally imbalanced plant stoichiometry?|journal=Trends in Ecology & Evolution|volume=17|issue=10|pages=457–461|doi=10.1016/S0169-5347(02)02587-9}}</ref><ref name="eLife 2014" /> including decreased B vitamins in rice.<ref name="Zhu2018">{{cite journal|display-authors=6|vauthors=Zhu C, Kobayashi K, Loladze I, Zhu J, Jiang Q, Xu X, Liu G, Seneweera S, Ebi KL, Drewnowski A, Fukagawa NK, Ziska LH|date=May 2018|title=2) levels this century will alter the protein, micronutrients, and vitamin content of rice grains with potential health consequences for the poorest rice-dependent countries|journal=Science Advances|volume=4|issue=5|pages=eaaq1012|doi=10.1126/sciadv.aaq1012|pmc=5966189|pmid=29806023}}</ref><ref>{{cite web|last=Milius|first=Susan|date=23 May 2018|title=As CO2 increases, rice loses B vitamins and other nutrients|url=https://www.sciencenews.org/article/carbon-dioxide-increases-rice-loses-b-vitamins-nutrients|access-date=2 July 2018|website=[[Sciencenews.org]]|name-list-style=vanc}}</ref> This may have knock-on effects on other parts of [[ecosystem]]s as herbivores will need to eat more food to gain the same amount of protein.<ref>{{cite journal|last1=Coviella|first1=Carlos E.|last2=Trumble|first2=John T.|year=1999|title=Effects of Elevated Atmospheric Carbon Dioxide on Insect-Plant Interactions|journal=Conservation Biology|volume=13|issue=4|pages=700–712|doi=10.1046/j.1523-1739.1999.98267.x|jstor=2641685|name-list-style=vanc}}</ref>
 
Climate change induced drought stress in Africa will likely lead to a reduction in the nutritional quality (lower micronutrient and higher anti-nutritional levels) of common bean<ref>{{Cite journal|last=Hummel|first=Marijke|last2=Hallahan|first2=Brendan F.|last3=Brychkova|first3=Galina|last4=Ramirez-Villegas|first4=Julian|last5=Guwela|first5=Veronica|last6=Chataika|first6=Bartholomew|last7=Curley|first7=Edna|last8=McKeown|first8=Peter C.|last9=Morrison|first9=Liam|last10=Talsma|first10=Elise F.|last11=Beebe|first11=Steve|date=2018-11-01|title=Reduction in nutritional quality and growing area suitability of common bean under climate change induced drought stress in Africa|url=https://www.nature.com/articles/s41598-018-33952-4|journal=Scientific Reports|language=en|volume=8|issue=1|pages=16187|doi=10.1038/s41598-018-33952-4|issn=2045-2322|pmc=PMC6212502|pmid=30385766}}</ref>. Studies have also shown that higher CO<sub>2</sub> levels lead to reduced plant uptake of nitrogen (and a smaller number showing the same for trace elements such as zinc) resulting in crops with lower nutritional value.<ref name="The Food, the Bad, and the Ugly">[http://www.grist.org/news/maindish/2005/07/12/scherer-plantchem/ The Food, the Bad, and the Ugly] ''Scherer, Glenn'' Grist July 2005</ref><ref>[https://www.newscientist.com/article/mg17623715-200-plague-of-plenty/ Plague of Plenty] New Scientist Archive</ref><ref>[https://www.politico.com/agenda/story/2017/09/13/food-nutrients-carbon-dioxide-000511/ The Great Nutrient Collapse] ''Bottemiller Evich, Helena'' Politico, 2017</ref> This would primarily impact on populations in poorer countries less able to compensate by eating more food, more varied diets, or possibly taking supplements.
 
Reduced nitrogen content in grazing plants has also been shown to reduce animal productivity in sheep, which depend on microbes in their gut to digest plants, which in turn depend on nitrogen intake.<ref name="The Food, the Bad, and the Ugly" /> Because of the lack of water available to crops in warmer countries they struggle to survive as they suffer from dehydration, taking into account the increasing demand for water outside of agriculture as well as other agricultural demands.<ref>{{Cite web|title=Climate Change and Irish Agriculture|url=http://eprints.maynoothuniversity.ie/2886/1/JS_Irish_Agriculture.pdf}}</ref>
 
=== Extreme weather ===
 
==== Rising temperatures ====
As the [[temperature]] changes and weather patterns become more extreme, areas which were historically good for farmland will no longer be as amicable.<ref name="Connor">{{cite journal|last1=Connor|first1=Jeffery D.|last2=Schwabe|first2=Kurt|last3=King|first3=Darran|last4=Knapp|first4=Keith|date=May 2012|title=Irrigated agriculture and climate change: The influence of water supply variability and salinity on adaptation|journal=[[Ecological Economics (journal)|Ecological Economics]]|volume=77|pages=149–157|doi=10.1016/j.ecolecon.2012.02.021}}</ref><ref name="Sindhu2">{{cite journal|last=Sindhu|first=J.S.|date=March 2011|title=Potential Impacts of Climate Change on Agriculture|url=http://www.indjst.org/index.php/indjst/article/view/29998/25953|journal=Indian Journal of Science and Technology|volume=4|issue=3|pages=348–353|doi=10.17485/ijst/2011/v4i3.32|issn=0974-6846|doi-access=free}}</ref> The current prediction is for temperature increase and precipitation decrease for major [[arid]] and [[Semi-arid climate|semi-arid]] regions ([[Middle East]], [[Africa]], [[Australia]], [[Southwest United States]], and [[Southern Europe]]).<ref name="Connor" /><ref name="Tubiello">{{cite journal|last1=Tubiello|first1=Francesco N.|last2=Rosenzweig|first2=Cynthia|year=2008|title=Developing climate change impact metrics for agriculture|url=http://journals.sfu.ca/int_assess/index.php/iaj/article/viewFile/276/240|journal=The Integrated Assessment Journal|volume=8|issue=1|pages=165–184}}</ref> In addition, crop yields in [[tropical regions]] will be negatively affected by the projected moderate increase in temperature (1-2&nbsp;°C) expected to occur during the first half of the century.<ref name="Tubiello & Soussana">{{cite journal|last1=Tubiello|first1=Francesco N.|last2=Soussana|first2=Jean-François|last3=Howden|first3=S. Mark|year=2007|title=Crop and pasture response to climate change|journal=[[Proceedings of the National Academy of Sciences]]|volume=104|issue=50|pages=19686–19690|bibcode=2007PNAS..10419686T|doi=10.1073/pnas.0701728104|pmc=2148358|pmid=18077401|doi-access=free}}</ref> During the second half of the century, further warming is projected to decrease [[crop]] yields in all regions including [[Canada]] and [[Northern United States]].<ref name="Tubiello" /> Many [[staple crop]]s are extremely sensitive to heat and when temperatures rise over 36&nbsp;°C, soybean seedlings are killed and corn pollen loses its vitality.<ref name="Ferber & Epstein" /><ref name="Thomson" /> Scientists project that an annual increase of 1&nbsp;°C will in turn decrease wheat, rice and corn yields by 10%.<ref name="Tubiello" /><ref name="Fischer & Shah">{{cite journal|last1=Fischer|first1=Günther|last2=Shah|first2=Mahendra|last3=Tubiello|first3=Francesco N.|last4=van Velhuizen|first4=Harrij|date=29 November 2005|title=Socio-economic and climate change impacts on agriculture: an integrated assessment, 1990–2080|journal=[[Philosophical Transactions of the Royal Society]]|volume=360|issue=1463|pages=2067–2083|doi=10.1098/rstb.2005.1744|pmc=1569572|pmid=16433094}}</ref>
 
There are, however, some positive possible aspects to climate change as well. The projected increase in temperature during the first half of the century (1-3&nbsp;°C) is expected to benefit crop and pasture yields in the [[temperate region]]s.<ref name="Hertel2">{{cite journal|last1=Hertel|first1=Thomas W.|last2=Rosch|first2=Stephanie D.|date=June 2010|title=Climate Change, Agriculture, and Poverty|url=http://ageconsearch.umn.edu/record/91437/files/Hertel_et_al._IATRC_Summer_2010.pdf|journal=[[Applied Economic Perspectives and Policy]]|volume=32|issue=3|pages=355–385|doi=10.1093/aepp/ppq016|hdl=10986/3949|s2cid=55848822|hdl-access=free}}</ref><ref name="Ferber & Epstein" /><ref name="Tubiello & Van der Velde">{{cite report|url=http://www.fao.org/fileadmin/templates/solaw/files/thematic_reports/TR_04a_web.pdf|title=Land and water use options for climate change adaptation and mitigation in agriculture|last1=Tubiello|first1=F.N.|last2=van der Velde|first2=M.|publisher=[[Food and Agriculture Organization]]|work=SOLAW Background Thematic Report - TR04A}}</ref> This will lead to higher winter temperatures and more frost-free days in these regions; resulting in a longer [[growing season]], increased thermal resources and accelerated maturation.<ref name="Kul2">{{cite journal|last=Kulshreshtha|first=Surendra N.|date=March 2011|title=Climate Change, Prairie Agriculture and Prairie Economy: The new normal|journal=Canadian Journal of Agricultural Economics|volume=59|issue=1|pages=19–44|doi=10.1111/j.1744-7976.2010.01211.x}}</ref><ref name="Canada">{{cite report|url=http://cfs.nrcan.gc.ca/pubwarehouse/pdfs/27428.pdf|title=Climate Change Impacts and Adaptation: A Canadian Perspective|date=2004|publisher=[[Natural Resources Canada]]|isbn=0-662-33123-0|editor1-first=Donald S.|editor1-last=Lemmen|editor2-first=Fiona J.|editor2-last=Warren}}{{page needed|date=August 2016}}</ref> If the climate scenario results in mild and wet weather, some areas and crops will suffer, but many may benefit from this.<ref name="Hertel2" />
 
==== Drought and flood ====
Extreme weather conditions continue to decrease crop yields in the form of [[droughts]] and [[floods]]. While these weather events are becoming more common, there is still uncertainty and therefore a lack of preparedness as to when and where they will take place.<ref name="Canada" /><ref name="Kristjanson2">{{cite journal|last1=Kristjanson|first1=Patti|last2=Neufeldt|first2=Henry|last3=Gassner|first3=Anja|last4=Mango|first4=Joash|last5=Kyazze|first5=Florence B.|last6=Desta|first6=Solomon|last7=Sayula|first7=George|last8=Thiede|first8=Brian|last9=Förch|first9=Wiebke|last10=Thornton|first10=Pphilip K.|last11=Coe|first11=Richard|display-authors=3|year=2012|title=Are food insecure smallholder households making changes in their farming practices? Evidence from East Africa|journal=Food Security|volume=4|issue=3|pages=381–397|doi=10.1007/s12571-012-0194-z|doi-access=free}}</ref> In extreme cases, floods destroy crops, disrupting agricultural activities and rendering workers jobless and eliminating food supply. On the opposite end of the spectrum, droughts can also wipe out crops. It is estimated that 35-50% of the world's crops are at risk of drought.<ref name="Ferber & Epstein" /> [[Drought in Australia|Australia]] has been experiencing severe, recurrent droughts for a number of years, bringing serious despair to its farmers. The country's rates of [[Depression (mood)|depression]] and [[domestic violence]] are increasing and as of 2007, more than one hundred farmers had committed suicide as their thirsty crops slipped away.<ref name="Ferber & Epstein" /> Drought is even more disastrous in the [[developing world]], exacerbating the pre-existing [[poverty]] and fostering [[famine]] and [[malnutrition]].<ref name="Hertel2" /><ref name="Ferber & Epstein" />
 
Droughts can cause farmers to rely more heavily on [[irrigation]]; this has downsides for both the individual farmers and the consumers. The equipment is expensive to install and some farmers may not have the financial ability to purchase it.<ref name="Connor" /> The water itself must come from somewhere and if the area has been in a drought for any length of time, the rivers may be dry and the water must be transported from further distances. With 70% of “blue water” currently being used for global agriculture, any need over and above this could potentiate a [[water crisis]].<ref name="Hertel2" /><ref name="Beddington" /> In [[Sub-Saharan Africa]], water is used to flood [[rice fields]] to control the weed population; with the projection of less precipitation for this area, this historical method of weed control will no longer be possible.<ref name="Rod10">{{cite journal|last1=Rodenburg|first1=Jonne|last2=Riches|first2=Charles R.|last3=Kayeke|first3=Juma M.|year=2010|title=Addressing current and future problems of parasitic weeds in rice|journal=Crop Protection|volume=29|issue=3|pages=210–221|doi=10.1016/j.cropro.2009.10.015}}</ref>
 
With more costs to the farmer, some will no longer find it financially feasible to farm. [[Agriculture]] employs the majority of the population in most low-income countries and increased costs can result in worker layoffs or pay cuts.<ref name="Hertel2" /> Other farmers will respond by raising their [[food prices]]; a cost which is directly passed on to the consumer and impacts the affordability of food. Some farms do not export their goods and their function is to feed a direct family or community; without that food, people will not have enough to eat. This results in decreased production, increased food prices, and potential starvation in parts of the world.<ref name="Beddington" />
 
==== Effect of hail ====
In North [[United States]], fewer hail days will occur overall due to climate change, but storms with larger hail might become more common (including hail that is larger than 1.6-inch).<ref name="nclimate3321">{{cite journal|last1=Brimelow|first1=Julian C.|last2=Burrows|first2=William R.|last3=Hanesiak|first3=John M.|name-list-style=vanc|date=26 June 2017|title=The changing hail threat over North America in response to anthropogenic climate change|journal=Nature Climate Change|volume=7|issue=7|pages=516–522|bibcode=2017NatCC...7..516B|doi=10.1038/nclimate3321}}</ref><ref>{{cite journal|vauthors=Botzen WJ, Bouwer LM, Van den Bergh JC|date=August 2010|title=Climate change and hailstorm damage: Empirical evidence and implications for agriculture and insurance|journal=Resource and Energy Economics|volume=32|issue=3|pages=341–362|doi=10.1016/j.reseneeco.2009.10.004}}</ref> Hail that is larger than 1.6-inch can quite easily break (glass) greenhouses.<ref>{{Cite web|last=Potenza|first=Alessandra|date=26 June 2017|title=Bigger hail might pummel the US as climate change gathers more force|url=https://www.theverge.com/2017/6/26/15873162/hailstorms-increase-north-america-climate-change-extreme-weather|website=The Verge}}</ref>
 
=== Heat stress of livestock ===
[[Heat stress]] on livestock has a devastating effect on not only their growth and reproduction, but their food intake and production of dairy and meat. Cattle require a temperature range of 5-15 degrees Celsius, but upwards to 25&nbsp;°C, to live comfortably, and once climate change increases the temperature, the chance of these changes occurring increases.<ref name="impact" /> Once the high temperatures hit, the livestock struggle to keep up their metabolism, resulting in decreased food intake, lowered activity rate, and a drop in weight. This causes a decline in livestock productivity and can be detrimental to the farmers and consumers. The location and species of the livestock varies and therefore the effects of heat vary between them. This is noted in livestock at a higher elevation and in the [[tropics]], of which have a generally increased effect from climate change. Livestock in a higher elevation are very vulnerable to high heat and are not well adapted to those changes.
 
=== Agricultural surfaces ===
Climate change may increase the amount of [[arable land]] in high-latitude region by reduction of the amount of frozen lands. A 2005 study reports that temperature in Siberia has increased three-degree Celsius in average since 1960 (much more than the rest of the world).<ref>German Research Indicates Warming in Siberia, Global Warming Today, Global Warming Today</ref> However, reports about the impact of global warming on Russian agriculture<ref>Federal Service for Hydrometeorology and Environmental Monitoring 5Roshydromet), Strategic Forecast of Climate Change in the Russian Federation 2010–2015 and Its Impact on Sectors of the Russian Economy (Moscow 2005)</ref> indicate conflicting probable effects: while they expect a northward extension of farmable lands,<ref>{{cite journal|last1=Kokorin|first1=Alexey O.|last2=Gritsevich|first2=Inna G.|year=2007|title=The Danger of Climate Change for Russia – Expected Losses and Recommendations|url=https://ethz.ch/content/dam/ethz/special-interest/gess/cis/center-for-securities-studies/pdfs/RAD-23-2-4.pdf|journal=Russian Analytical Digest|issue=23|pages=2–4|name-list-style=vanc}}</ref> they also warn of possible productivity losses and increased risk of drought.<ref>{{cite news|last1=Pearce|first1=Fred|date=3 October 2003|title=Global warming 'will hurt Russia'|work=New Scientist|url=https://www.newscientist.com/article/dn4232-global-warming-will-hurt-russia/}}</ref>
 
Sea levels are expected to get up to one meter higher by 2100, though this projection is disputed. A rise in the sea level would result in an agricultural [[land consumption|land loss]], in particular in areas such as [[South East Asia]]. [[Erosion]], [[sea level rise|submergence of shorelines]], [[salinity]] of the [[water table]] due to the increased sea levels, could mainly affect agriculture through [[inundation]] of [[depression (geology)|low-lying lands]].
 
Low-lying areas such as Bangladesh, India and Vietnam will experience major loss of rice crop if sea levels rise as expected by the end of the century. Vietnam for example relies heavily on its southern tip, where the Mekong Delta lies, for rice planting. Any rise in sea level of no more than a meter will drown several km<sup>2</sup> of rice paddies, rendering Vietnam incapable of producing its main staple and export of rice.<ref>{{cite journal|last=Wassmann|first=Reiner|date=July–September 2007|title=Coping With Climate Change|url=http://www.irri.org/publications/today/pdfs/6-3/10-15.pdf|url-status=dead|journal=Rice Today|publisher=IRRI|pages=10–15|archive-url=https://web.archive.org/web/20090327094148/http://www.irri.org/publications/today/pdfs/6-3/10-15.pdf|archive-date=27 March 2009|access-date=7 October 2009|name-list-style=vanc}}</ref>
 
=== Erosion and fertility ===
The warmer atmospheric temperatures observed over the past decades are expected to lead to a more vigorous hydrological cycle, including more extreme rainfall events. [[Erosion]] and [[soil degradation]] is more likely to occur. Soil [[fertility]] would also be affected by global warming. Increased erosion in agricultural landscapes from anthropogenic factors can occur with losses of up to 22% of soil carbon in 50 years.<ref>{{Cite journal|last1=Doetterl|first1=Sebastian|last2=Oost|first2=Kristof Van|last3=Six|first3=Johan|date=1 May 2012|title=Towards constraining the magnitude of global agricultural sediment and soil organic carbon fluxes|journal=Earth Surface Processes and Landforms|language=en|volume=37|issue=6|pages=642–655|bibcode=2012ESPL...37..642D|doi=10.1002/esp.3198|issn=1096-9837|name-list-style=vanc|hdl=2078.1/123112}}</ref> However, because the ratio of soil organic carbon to nitrogen is mediated by [[soil biology]] such that it maintains a narrow range, a doubling of soil organic carbon is likely to imply a doubling in the storage of [[nitrogen]] in soils as organic nitrogen, thus providing higher available nutrient levels for plants, supporting higher yield potential. The demand for imported fertilizer nitrogen could decrease, and provide the opportunity for changing costly [[fertilisation]] strategies.
 
Due to the extremes of climate that would result, the increase in precipitations would probably result in greater risks of erosion, whilst at the same time providing soil with better hydration, according to the intensity of the rain. The possible evolution of the [[organic matter]] in the soil is a highly contested issue: while the increase in the temperature would induce a greater rate in the production of [[minerals]], lessening the [[soil organic matter]] content, the atmospheric CO<sub>2</sub> concentration would tend to increase it.
 
=== Glacier retreat and disappearance ===
The continued [[Effects of global warming#Cryosphere|retreat of glaciers]] will have a number of different quantitative impacts. In the areas that are heavily dependent on [[Surface runoff|water runoff]] from [[glaciers]] that melt during the warmer summer months, a continuation of the current retreat will eventually deplete the glacial ice and substantially reduce or eliminate runoff. A reduction in runoff will affect the ability to [[irrigation|irrigate]] crops and will reduce summer stream flows necessary to keep dams and reservoirs replenished.
 
Approximately 2.4&nbsp;billion people live in the [[drainage basin]] of the Himalayan rivers.<ref>{{cite web|title=Big melt threatens millions, says UN|url=http://www.peopleandplanet.net/pdoc.php?id=3024|archive-url=https://web.archive.org/web/20080219045312/http://www.peopleandplanet.net/pdoc.php?id=3024|archive-date=19 February 2008|work=People & the Planet}}</ref> [[India]], [[China]], [[Pakistan]], [[Afghanistan]], [[Bangladesh]], [[Nepal]] and [[Myanmar]] could experience floods followed by severe droughts in coming decades.<ref>{{cite web|title=Glaciers melting at alarming speed|url=http://english.peopledaily.com.cn/90001/90781/90879/6222327.html|work=People's Daily Online}}</ref> In [[India]] alone, the [[Ganges]] provides water for drinking and farming for more than 500 million people.<ref>{{cite web|date=24 July 2007|title=Ganges, Indus may not survive: climatologists|url=http://www.rediff.com/news/2007/jul/24indus.htm|work=Rediff.com India Limited}}</ref><ref>{{cite news|date=10 November 2004|title=Himalaya glaciers melt unnoticed|url=http://news.bbc.co.uk/2/hi/science/nature/3998967.stm|via=bbc.co.uk}}</ref> The west coast of North America, which gets much of its water from glaciers in mountain ranges such as the [[Rocky Mountains]] and [[Sierra Nevada (U.S.)|Sierra Nevada]], also would be affected.<ref>{{cite web|title=Glaciers Are Melting Faster Than Expected, UN Reports|url=https://www.sciencedaily.com/releases/2008/03/080317154235.htm|work=ScienceDaily}}</ref>
 
=== Financial ===
Some research suggests that initially climate change will help developing nations because some regions will be experiencing more negative climate change effects which will result in increased demand for food leading to higher prices and increased wages.<ref name="Hertel2" /> However, many of the projected [[Climate change scenario|climate scenarios]] suggest a huge financial burden. For example, the [[2003 European heat wave|heat wave that passed through Europe in 2003]] cost 13 billion euros in uninsured agriculture losses.<ref name="Tubiello & Soussana" /> In addition, during [[El Nino]] weather conditions, the chance of the Australian farmer's income falling below average increased by 75%, greatly impacting the country's [[GDP]].<ref name="Tubiello & Soussana" /> The agriculture industry in [[India]] makes up 52% of their employment and the [[Canadian Prairies]] supply 51% of Canadian agriculture; any changes in the production of food crops from these areas could have profound effects on the [[economy]].<ref name="Kul2" /><ref name="Sindhu2" /> This could negatively affect the affordability of food and the subsequent health of the population.
 
=== Ozone and UV-B ===
Some scientists think agriculture could be affected by any decrease in [[stratospheric ozone]], which could increase biologically dangerous [[ultraviolet|ultraviolet radiation B]]. Excess ultraviolet radiation B can directly affect [[plant physiology]] and cause massive amounts of [[mutation]]s, and indirectly through changed [[pollinator]] behavior, though such changes are not simple to quantify.<ref>{{cite news|last=Brown|first=Paul|date=26 April 2005|title=Ozone layer least fragile on record|work=The Guardian|url=https://www.theguardian.com/uk_news/story/0,,1470944,00.html|name-list-style=vanc}}</ref> However, it has not yet been ascertained whether an increase in greenhouse gases would decrease stratospheric ozone levels.
 
In addition, a possible effect of rising temperatures is significantly higher levels of [[tropospheric ozone|ground-level ozone]], which would substantially lower yields.<ref>{{cite web|last=McCarthy|first=Michael|date=27 April 2005|title=Climate change poses threat to food supply, scientists say|url=http://news.independent.co.uk/world/environment/story.jsp?story%3D633349|url-status=dead|archive-url=https://web.archive.org/web/20050627000215/http://news.independent.co.uk/world/environment/story.jsp?story=633349|archive-date=27 June 2005|access-date=7 October 2009|work=The Independent|name-list-style=vanc}}</ref>
 
=== ENSO effects on agriculture ===
ENSO ([[El Niño Southern Oscillation]]) will affect monsoon patterns more intensely in the future as climate change warms up the ocean's water. Crops that lie on the equatorial belt or under the tropical Walker circulation, such as rice, will be affected by varying monsoon patterns and more unpredictable weather. Scheduled planting and harvesting based on weather patterns will become less effective.
 
Areas such as Indonesia where the main crop consists of rice will be more vulnerable to the increased intensity of ENSO effects in the future of climate change. University of Washington professor, [[David Battisti]], researched the effects of future ENSO patterns on the [[Indonesia]]<nowiki/>n rice agriculture using [IPCC]'s 2007 annual report<ref>IPCC. Climate Change 2007: Synthesis Report. United Nations Environment Programme, 2007:Ch5, 8, and 10.[http://www.ipcc.ch/pdf/assessment-report/ar4/syr/ar4_syr.pdf]</ref> and 20 different logistical models mapping out climate factors such as wind pressure, sea-level, and humidity, and found that rice harvest will experience a decrease in yield. Bali and Java, which holds 55% of the rice yields in Indonesia, will be likely to experience 9–10% probably of delayed monsoon patterns, which prolongs the hungry season. Normal planting of rice crops begin in October and harvest by January. However, as climate change affects ENSO and consequently delays planting, harvesting will be late and in drier conditions, resulting in less potential yields.<ref>{{cite journal|vauthors=Naylor RL, Battisti DS, Vimont DJ, Falcon WP, Burke MB|date=May 2007|title=Assessing risks of climate variability and climate change for Indonesian rice agriculture|journal=Proceedings of the National Academy of Sciences of the United States of America|volume=104|issue=19|pages=7752–7|bibcode=2007PNAS..104.7752N|doi=10.1073/pnas.0701825104|pmc=1876519|pmid=17483453|doi-access=free}}</ref>
 
=== Projections of impacts ===
{{update section|reason=change from 4th assessment report to more recent sources|date=July 2019}}
As part of the IPCC's [[IPCC Fourth Assessment Report|Fourth Assessment Report]], Schneider et al. (2007) [[Global climate model#Projections of future climate change|projected]] the potential future effects of climate change on agriculture.<ref name=tab191>{{cite book | vauthors = Schneider SH | contribution = 19.3.1 Introduction to Table 19.1 | title = Chapter 19: Assessing Key Vulnerabilities and the Risk from Climate Change | series = Climate change 2007: impacts, adaptation and vulnerability: contribution of Working Group II to the fourth assessment report of the Intergovernmental Panel on Climate Change | url = http://www.ipcc.ch/publications_and_data/ar4/wg2/en/ch19s19-3-1.html | veditors = Parry ML | publisher = Print version: CUP. This version: IPCC website | year = 2007 | location = Cambridge University Press (CUP): Cambridge, UK | isbn = 978-0-521-88010-7 | access-date = 4 May 2011 | display-editors = etal | archive-url = https://web.archive.org/web/20130312103028/http://www.ipcc.ch/publications_and_data/ar4/wg2/en/ch19s19-3-1.html | archive-date = 12 March 2013 | url-status = dead }}</ref> With low to medium confidence, they concluded that for about a 1 to 3&nbsp;°C global mean temperature increase (by 2100, relative to the 1990–2000 average level) there would be productivity decreases for some cereals in low latitudes, and productivity increases in high latitudes. In the IPCC Fourth Assessment Report, "low confidence" means that a particular finding has about a 2 out of 10 chance of being correct, based on expert judgement. "Medium confidence" has about a 5 out of 10 chance of being correct.<ref name="parry uncertainty assessment">{{cite book | vauthors = Parry ML | contribution = Box TS.2. Communication of uncertainty in the Working Group II Fourth Assessment | title = Technical summary | series = Climate change 2007: impacts, adaptation and vulnerability: contribution of Working Group II to the fourth assessment report of the Intergovernmental Panel on Climate Change | url = http://www.ipcc.ch/publications_and_data/ar4/wg2/en/tssts-1.html | veditors = Parry ML | publisher = Print version: CUP. This version: IPCC website | year = 2007 | location = Cambridge University Press (CUP): Cambridge, UK | isbn = 978-0-521-88010-7 | access-date = 4 May 2011 | display-editors = etal | archive-url = https://web.archive.org/web/20110608055450/http://www.ipcc.ch/publications_and_data/ar4/wg2/en/tssts-1.html | archive-date = 8 June 2011 | url-status = dead }}</ref> Over the same time period, with medium confidence, global production potential was projected to:<ref name=tab191/>
* increase up to around 3&nbsp;°C,
* very likely decrease above about 3&nbsp;°C.
 
Most of the studies on global agriculture assessed by Schneider et al. (2007) had not incorporated a number of critical factors, including changes in extreme events, or the spread of pests and diseases. Studies had also not considered the development of specific practices or technologies to aid [[adaptation to global warming#Agricultural production|adaptation to climate change]].<ref>{{cite book | vauthors = Schneider SH | contribution = 19.3.2.1 Agriculture | title = Chapter 19: Assessing Key Vulnerabilities and the Risk from Climate Change | series = Climate change 2007: impacts, adaptation and vulnerability: contribution of Working Group II to the fourth assessment report of the Intergovernmental Panel on Climate Change | url = http://www.ipcc.ch/publications_and_data/ar4/wg2/en/ch19s19-3-2-1.html | veditors = Parry ML | publisher = Print version: CUP. This version: IPCC website | year = 2007 | page = 790 | location = Cambridge University Press (CUP): Cambridge, UK | isbn = 978-0-521-88010-7 | access-date = 4 May 2011 | display-editors = etal | archive-url = https://web.archive.org/web/20120819151402/http://www.ipcc.ch/publications_and_data/ar4/wg2/en/ch19s19-3-2-1.html | archive-date = 19 August 2012 | url-status = dead }}</ref>
 
The [[US National Research Council]] (US NRC, 2011)<ref name="us nrc 2011 fig 5.1">
[http://www.nap.edu/openbook.php?record_id=12877&page=161 Figure 5.1], p.161, in: Sec 5.1 FOOD PRODUCTION, PRICES, AND HUNGER, in: Ch 5: Impacts in the Next Few Decades and Coming Centuries, in: {{harvnb|US NRC|2011}}
</ref> assessed the literature on the effects of climate change on crop yields. US NRC (2011)<ref name="us nrc 2011 text">
Sec 5.1 FOOD PRODUCTION, PRICES, AND HUNGER, [http://www.nap.edu/openbook.php?record_id=12877&page=160 pp.160-162], in: Ch 5: Impacts in the Next Few Decades and Coming Centuries, in {{harvnb|US NRC|2011}}
</ref> stressed the uncertainties in their projections of changes in crop yields. A meta-analysis in 2014 revealed consensus that yield is expected to decrease in the second half of the century, and with greater effect in tropical than temperate regions.<ref>{{Cite journal|last1=Challinor|first1=A. J.|last2=Watson|first2=J.|last3=Lobell|first3=D. B.|last4=Howden|first4=S. M.|last5=Smith|first5=D. R.|last6=Chhetri|first6=N.|date=2014|title=A meta-analysis of crop yield under climate change and adaptation|journal=Nature Climate Change|language=en|volume=4|issue=4|pages=287–291|doi=10.1038/nclimate2153|bibcode=2014NatCC...4..287C|issn=1758-678X|url=http://eprints.whiterose.ac.uk/78340/13/Challinor-etal-AR5-RevisionsFinal_with_coversheet.pdf}}</ref>
 
Writing in the journal ''[[Nature Climate Change]]'', Matthew Smith and Samuel Myers (2018) estimated that food crops could see a reduction of [[protein]], [[iron]] and [[zinc]] content in common food crops of 3 to 17%.<ref>{{Cite journal|last1=Smith|first1=Matthew R.|last2=Myers|first2=Samuel S. | name-list-style = vanc |date=27 August 2018|title=Impact of anthropogenic CO2 emissions on global human nutrition|journal=Nature Climate Change|language=En|volume=8|issue=9|pages=834–839|doi=10.1038/s41558-018-0253-3|issn=1758-678X|bibcode=2018NatCC...8..834S|s2cid=91727337}}</ref> This is the projected result of food grown under the expected atmospheric carbon-dioxide levels of 2050. Using data from the [[Food and Agriculture Organization|UN Food and Agriculture Organization]] as well as other public sources, the authors analyzed 225 different staple foods, such as [[wheat]], [[rice]], [[maize]], [[vegetable]]s, roots and [[fruit]]s.<ref>{{Cite web|url=https://www.theguardian.com/science/2018/aug/27/climate-change-will-make-hundreds-of-millions-more-people-nutrient-deficient|title=Climate change will make hundreds of millions more people nutrient deficient|last=Davis|first=Nicola| name-list-style = vanc |date=27 August 2018|website=the Guardian|language=en|access-date=29 August 2018}}</ref> The effect of projected for this century levels of atmospheric carbon dioxide on the nutritional quality of plants is not limited only to the above-mentioned crop categories and nutrients. A 2014 meta-analysis has shown that crops and wild plants exposed to elevated carbon dioxide levels at various latitudes have lower density of several minerals such as magnesium, iron, zinc, and potassium.<ref name="eLife 2014">{{Cite journal|last=Loladze|first=Irakli| name-list-style = vanc |date=7 May 2014|title=Hidden shift of the ionome of plants exposed to elevated CO2 depletes minerals at the base of human nutrition| journal=eLife|language=En|volume=3|issue=9|pages=e02245|doi=10.7554/eLife.02245|pmid=24867639|pmc=4034684}}</ref>
 
{|
| [[File:Projected changes in crop yields at different latitudes with global warming.png|thumb|upright=2|alt=Refer to caption|Projected changes in crop yields at different latitudes with global warming. This graph is based on several studies.<ref name="us nrc 2011 fig 5.1"/>]]
| [[File:Projected changes in yields of selected crops with global warming.png|thumb|upright=2|alt=Refer to caption|Projected changes in yields of selected crops with global warming. This graph is based on several studies.<ref name="us nrc 2011 fig 5.1"/>]]
|}
 
Their central estimates of changes in crop yields are shown above. Actual changes in yields may be above or below these central estimates.<ref name="us nrc 2011 text"/> US NRC (2011)<ref name="us nrc 2011 fig 5.1"/> also provided an estimated the "likely" range of changes in yields. "Likely" means a greater than 67% chance of being correct, based on expert judgement. The likely ranges are summarized in the image descriptions of the two graphs.
 
====Food security====
The [[IPCC Fourth Assessment Report]] also describes the impact of climate change on [[food security]].<ref name="easterling sub saharan africa">{{cite book | vauthors = Easterling WE | contribution = 5.6.5 Food security and vulnerability | title = Chapter 5: Food, Fibre, and Forest Products | series = Climate change 2007: impacts, adaptation and vulnerability: contribution of Working Group II to the fourth assessment report of the Intergovernmental Panel on Climate Change | url = http://www.ipcc.ch/publications_and_data/ar4/wg2/en/ch5s5-6-5.html | veditors = Parry ML | year = 2007 | publisher = Cambridge University Press | isbn = 978-0-521-88010-7 | display-editors = etal | access-date = 25 June 2011 | archive-url = https://web.archive.org/web/20181102224228/http://www.ipcc.ch/publications_and_data/ar4/wg2/en/ch5s5-6-5.html | archive-date = 2 November 2018 | url-status = dead }}</ref> Projections suggested that there could be large decreases in [[hunger]] globally by 2080, compared to the (then-current) 2006 level.<ref name="easterling food security">{{cite book | vauthors = Easterling WE | contribution = Executive summary | title = Chapter 5: Food, Fibre, and Forest Products | series = Climate change 2007: impacts, adaptation and vulnerability: contribution of Working Group II to the fourth assessment report of the Intergovernmental Panel on Climate Change | url = http://www.ipcc.ch/publications_and_data/ar4/wg2/en/ch5s5-es.html | veditors = Parry ML | year = 2007 | publisher = Cambridge University Press | isbn = 978-0-521-88010-7 | display-editors = etal | access-date = 9 January 2013 | archive-url = https://web.archive.org/web/20130312073614/http://ipcc.ch/publications_and_data/ar4/wg2/en/ch5s5-es.html | archive-date = 12 March 2013 | url-status = dead }}</ref> Reductions in hunger were driven by projected [[social change|social]] and [[economic development]]. For reference, the [[Food and Agriculture Organization]] has estimated that in 2006, the number of people undernourished globally was 820 million.<ref>
{{cite web
| date=30 October 2006
| title=World hunger increasing
| publisher=Food and Agriculture Organization (FAO) Newsroom
| url=http://www.fao.org/newsroom/en/news/2006/1000433/index.html
| access-date=7 July 2011}}
</ref> Three [[climate change scenario|scenarios]] ''without'' climate change ([[Special Report on Emissions Scenarios|SRES]] A1, B1, B2) projected 100-130 million undernourished by the year 2080, while another scenario without climate change (SRES A2) projected 770 million undernourished. Based on an expert assessment of all of the evidence, these projections were thought to have about a 5-in-10 chance of being correct.<ref name="parry uncertainty assessment"/>
 
The same set of greenhouse gas and socio-economic scenarios were also used in projections that included the effects of climate change.<ref name="easterling food security"/> ''Including'' climate change, three scenarios (SRES A1, B1, B2) projected 100-380 million undernourished by the year 2080, while another scenario with climate change (SRES A2) projected 740–1,300 million undernourished. These projections were thought to have between a 2-in-10 and 5-in-10 chance of being correct.<ref name="parry uncertainty assessment"/>
 
Projections also suggested regional changes in the global distribution of hunger.<ref name="easterling food security"/> By 2080, [[sub-Saharan Africa]] may overtake [[Asia]] as the world's most food-insecure region. This is mainly due to projected social and economic changes, rather than climate change.<ref name="easterling sub saharan africa"/>
 
In [[South America]], a phenomenon known as the [[El Niño–Southern Oscillation]] Cycle, between floods and drought on the Pacific Coast has made as much as a 35% difference in Global yields of wheat and grain.<ref>Howden, M. e. (2007). Adapting Agriculture to Climate Change. Proceedings of the National Academy of Sciences of the United States of America 104/50, 19691-19696</ref>
 
Looking at the four key components of [[Food]] security we can see the impact climate change has had. "Access to food is largely a matter of household and individual-level income and of capabilities and rights" (Wheeler et al.,2013). Access has been affected by the thousands of crops being destroyed, how communities are dealing with climate shocks and adapting to climate change. Prices on food will rise due to the shortage of food production due to conditions not being favourable for crop production. Utilization is affected by floods and drought where water resources are contaminated, and the changing temperatures create vicious stages and phases of disease. Availability is affected by the contamination of the crops, as there will be no food process for the products of these crops as a result. Stability is affected through price ranges and future prices as some food sources are becoming scarce due to climate change, so prices will rise.
 
====Individual studies====
[[File:Projected effect of climate change on agricultural productivity for different regions (Cline, 2007).png|alt=Refer to caption and adjacent text|thumb|upright=2|right|Projections by Cline (2008)<ref name="cline projections"/>]]
Cline (2008)<ref name="cline projections">
{{harvnb|Cline|2008}}
</ref> looked at how [[climate change]] might affect agricultural productivity in the 2080s. His study assumes that no efforts are made to reduce anthropogenic greenhouse gas emissions, leading to global warming of 3.3&nbsp;°C above the pre-industrial level. He concluded that global agricultural productivity could be negatively affected by climate change, with the worst effects in developing countries (see graph opposite).
 
Lobell et al. (2008a)<ref>
{{harvnb|Lobell|others|2008a}} (paywall). {{harvnb|Lobell|others|2008b}} can be freely accessed.
</ref> assessed how climate change might affect 12 food-insecure regions in 2030. The purpose of their analysis was to assess where adaptation measures to climate change should be prioritized. They found that without sufficient adaptation measures, South Asia and South [[Africa]] would likely suffer negative impacts on several crops which are important to large food insecure human populations.
 
Battisti and Naylor (2009)<ref name="battisti seasonal temp">{{harvnb|Battisti|Naylor|2009}}</ref> looked at how increased seasonal temperatures might affect agricultural productivity. Projections by the IPCC suggest that with climate change, high seasonal temperatures will become widespread, with the likelihood of extreme temperatures increasing through the second half of the 21st century. Battisti and Naylor (2009)<ref name="battisti seasonal temp"/> concluded that such changes could have very serious effects on agriculture, particularly in the tropics. They suggest that major, near-term, investments in adaptation measures could reduce these risks.
 
"[[Climate change]] merely increases the urgency of reforming trade policies to ensure that global [[food security]] needs are met"<ref name="ictsd">[http://ictsd.org/i/press/press-releases/61231/ Ending hunger will require trade policy reform], Press Release, International Centre for Trade and Sustainable Development, 12 October 2009.</ref> said C. Bellmann, ICTSD Programmes Director. A 2009 ICTSD-IPC study by Jodie Keane<ref name="study">[http://ictsd.org/downloads/2009/10/draft-ictsd-ipc-paper.pdf Climate change, agriculture and aid for trade], by Jodie Keane, ICTSD-IPC</ref> suggests that [[climate change]] could cause farm output in [[sub-Saharan Africa]] to decrease by 12% by 2080 - although in some African countries this figure could be as much as 60%, with [[Agreement on Agriculture|agricultural exports]] declining by up to one fifth in others. Adapting to [[climate change]] could cost the agriculture sector $14bn globally a year, the study finds.
 
==== Crop development models ====
 
Models for climate behavior are frequently inconclusive. In order to further study effects of global warming on agriculture, other types of models, such as ''crop development models'', ''yield prediction'', quantities of ''water or fertilizer consumed'', can be used. Such models condense the knowledge accumulated of the climate, soil, and effects observed of the results of various [[agricultural practices]]. They thus could make it possible to test strategies of adaptation to modifications of the environment.
 
Because these models are necessarily simplifying natural conditions (often based on the assumption that weeds, disease and insect [[pest (animal)|pests]] are controlled), it is not clear whether the results they give will have an ''in-field'' reality. However, some results are partly validated with an increasing number of experimental results.
 
Other models, such as ''insect and disease development'' models based on climate projections are also used (for example simulation of [[aphid]] reproduction or [[septoria]] (cereal fungal disease) development).
 
Scenarios are used in order to estimate climate changes effects on crop development and yield. Each scenario is defined as a set of [[meteorological]] variables, based on generally accepted projections. For example, many models are running simulations based on doubled [[carbon dioxide]] projections, temperatures raise ranging from 1&nbsp;°C up to 5&nbsp;°C, and with rainfall levels an increase or decrease of 20%. Other parameters may include [[humidity]], wind, and [[solar variation|solar activity]]. Scenarios of crop models are testing farm-level adaptation, such as sowing date shift, climate adapted species ([[vernalisation]] need, heat and cold resistance), [[irrigation]] and fertilizer adaptation, resistance to disease. Most developed models are about wheat, maize, rice and [[soybean]].
 
==== Poverty alleviation ====
Researchers at the [[Overseas Development Institute]] (ODI) have investigated the potential impacts climate change could have on agriculture, and how this would affect attempts at alleviating poverty in the [[developing world]].<ref name="ccandpoverty">{{cite web|year=2007|title=Climate change, agricultural policy and poverty reduction – how much do we know?|url=http://www.odi.org.uk/resources/details.asp?id=1231&title=climate-change-agricultural-policy-poverty-reduction-much-know|publisher=[[Overseas Development Institute]]}}</ref> They argued that the effects from moderate climate change are likely to be mixed for developing countries. However, the vulnerability of the poor in developing countries to short-term impacts from climate change, notably the increased frequency and severity of adverse weather events is likely to have a negative impact. This, they say, should be taken into account when defining [[agricultural policy]].<ref name="ccandpoverty" />
 
==Regional impacts==
{{See also|Regional effects of climate change}}
 
=== Africa ===
{{Further|Climate change in Africa}}
[[File:African crop production.png|thumb|African crop production. Raw data from the United Nations.<ref name="fao.org"/>]]
Agriculture is a particularly important sector in Africa, contributing towards livelihoods and economies across the continent. On average, agriculture in Sub-Saharan Africa contributes 15% of the total GDP.<ref name=":2">{{Cite book|title=OECD‑FAO Agricultural Outlook 2016‑2025|last=OECD/FAO|publisher=OECD Publishing|year=2016|isbn=978-92-64-25323-0|url=http://www.fao.org/3/a-i5778e.pdf|pages=59–61}}</ref> Africa's geography makes it particularly vulnerable to climate change, and 70% of the population rely on [[Rainfed agriculture|rain-fed agriculture]] for their livelihoods. [[Smallholding|Smallholder]] farms account for 80% of cultivated lands in Sub-Saharan Africa.<ref>{{cite journal |last1=Jellason |first1=Nugun P. |last2=Robinson |first2=Elizabeth J. Z. |last3=Ogbaga |first3=Chukwuma C. |title=Agriculture 4.0: Is Sub-Saharan Africa Ready? |journal=Applied Sciences |date=21 June 2021 |volume=11 |issue=12 |pages=5750 |doi=10.3390/app11125750|doi-access=free }}</ref><ref name=":2" /> The Intergovernmental Panel on Climate Change (IPCC) (2007:13)<ref name="ar4 summary of regional impacts">
{{cite book|title=Climate Change 2007: Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change | veditors = Parry ML, etal |author=IPCC|publisher=Cambridge University Press|year=2007|chapter=Summary for Policymakers: C. Current knowledge about future impacts|chapter-url=http://www.ipcc.ch/publications_and_data/ar4/wg2/en/spmsspm-c.html}}
</ref> projected that climate variability and change would severely compromise agricultural productivity and access to food. This projection was assigned "high confidence". Cropping systems, livestock and fisheries will be at greater risk of pest and diseases as a result of future climate change.<ref name=":3">{{Cite journal| vauthors = Dhanush D, Bett BK, Boone RB, Grace D, Kinyangi J, Lindahl JF, Mohan CV, Ramírez Villegas J, Robinson TP, Rosenstock TS, Smith J |date=2015|title=Impact of climate change on African agriculture: focus on pests and diseases|url=https://cgspace.cgiar.org/rest/bitstreams/55241/retrieve|journal=CGIAR Research Program on Climate Change, Agriculture and Food Security (CCAFS)}}</ref> Research program on Climate Change, Agriculture and Food Security (CCAFS) have identified that crop pests already account for approximately 1/6th of farm productivity losses.<ref name=":3" /> Similarly, climate change will accelerate the prevalence of pests and diseases and increase the occurrence of highly impactful events.<ref name=":3" /> The impacts of climate change on agricultural production in Africa will have serious implications for food security and livelihoods. Between 2014 and 2018, Africa had the highest levels of food insecurity in the world.<ref>{{Cite web|url=http://www.fao.org/state-of-food-security-nutrition/en/|title=SOFI 2019 - The State of Food Security and Nutrition in the World|website=www.fao.org|publisher=Food and Agriculture Organization of the United Nations|language=en|access-date=8 August 2019}}</ref>
 
According to a study of [[East Africa]]’s [[Smallholding|smallholder]] farms, impacts of climate change on agriculture are already being seen there resulting in changes to farming practices such as [[intercropping]], crop, soil, land, water and livestock management systems, and introduction of new technologies and seed varieties by some of the farmers.<ref name="Kristjanson2"/> Some other suggestions such as eliminating [[supply chain]] and household [[food waste]], encouraging diverse and vegetable-rich diets, and providing global access to foods ([[food aid]] programs) have been suggested as ways to adapt.<ref name="Hertel">{{cite journal|last1=Hertel|first1=Thomas W.|last2=Rosch|first2=Stephanie D.|date=June 2010|title=Climate Change, Agriculture, and Poverty|url=http://ageconsearch.umn.edu/record/91437/files/Hertel_et_al._IATRC_Summer_2010.pdf|journal=[[Applied Economic Perspectives and Policy]]|volume=32|issue=3|pages=355–385|doi=10.1093/aepp/ppq016|hdl=10986/3949|s2cid=55848822|hdl-access=free}}</ref><ref name="Beddington">{{cite journal|last1=Beddington|first1=John R.|last2=Asaduzzaman|first2=Mohammed|last3=Clark|first3=Megan E.|last4=Bremauntz|first4=Adrian Fernández|last5=Guillou|first5=Marion D|last6=Jahn|first6=Molly M.|last7=Lin|first7=Erda|last8=Mamo|first8=Tekalign|last9=Negra|first9=Christine|last10=Nobre|first10=Carlos A.|last11=Scholes|first11=Robert J.|display-authors=3|year=2012|title=The role for scientists in tackling food insecurity and climate change|journal=Agriculture & Food Security|volume=1|issue=10|pages=10|doi=10.1186/2048-7010-1-10|doi-access=free|first12=Rita|last13=Van Bo|first13=Nguyen|last14=Wakhungu|first14=Judi|last12=Sharma}}</ref><ref name="Chakra">{{cite journal|last1=Chakraborty|first1=S.|last2=Newton|first2=A. C.|date=10 January 2011|title=Climate change, plant diseases and food security: an overview|journal=Plant Pathology|volume=60|issue=1|pages=2–14|doi=10.1111/j.1365-3059.2010.02411.x|doi-access=free}}</ref> Many researchers agree that agricultural innovation is essential to addressing the potential issues of climate change. This includes better management of soil, water-saving technology, matching crops to environments, introducing different crop varieties, crop rotations, appropriate [[fertilization]] use, and supporting community-based adaptation strategies.<ref name="Kul2"/><ref name="Beddington" /><ref name="Sindhu2"/><ref name="Rod112"/><ref name="IFPRI">{{cite report|url=http://ebrary.ifpri.org/utils/getfile/collection/p15738coll2/id/16557/filename/16558.pdf|title=Climate Change: Impact on Agriculture and Costs of Adaptation|last1=Nelson|first1=Gerald C.|last2=Rosegrant|first2=Mark W.|date=October 2009|publisher=[[International Food Policy Research Institute]]|location=Washington, DC|last3=Koo|first3=Jawoo|last4=Robertson|first4=Richard|last5=Sulser|first5=Timothy|last6=Zhu|first6=Tingju|last7=Ringler|first7=Claudia|last8=Msangi|first8=Siwa|last9=Palazzo|first9=Amanda|access-date=12 August 2016|archive-url=http://webarchive.loc.gov/all/20160505014731/http%3A//ebrary.ifpri.org/utils/getfile/collection/p15738coll2/id/16557/filename/16558.pdf|archive-date=5 May 2016|display-authors=3|last10=Batka|last14=Lee|first14=David|last13=Ewing|first13=Mandy|last12=Valmonte-Santos|first12=Rowena|last11=Magalhaes|first11=Marilia|first10=Miroslav|url-status=dead}}</ref> On a government and global level, research and investments into [[agricultural productivity]] and [[infrastructure]] must be done to get a better picture of the issues involved and the best methods to address them. [[Government policies]] and programs must provide environmentally sensitive government [[subsidies]], educational campaigns and economic incentives as well as funds, [[insurance]] and safety nets for vulnerable populations.<ref name="Hertel" /><ref name="Beddington" /><ref name="Chakra" /><ref name="Sindhu2"/><ref name="IFPRI" /> In addition, providing [[early warning systems]], and accurate [[weather forecasts]] to poor or remote areas will allow for better preparation; by using and sharing the available technology, the global issue of climate change can be addressed and mitigated by the global community.<ref name="Beddington" />
 
==== East Africa ====
{{See also|Sudanese nomadic conflicts}}
In East Africa, climate change is anticipated to intensify the frequency and intensity of drought and flooding, which can have an adverse impact on the agricultural sector. Climate change will have varying effects on agricultural production in East Africa. Research from the International Food Policy Research Institute (IFPRI) suggest an increase in maize yields for most East Africa, but yield losses in parts of Ethiopia, Democratic Republic of Congo (DRC), Tanzania and northern Uganda.<ref>{{Cite web|url=http://www.ifpri.org/publication/east-african-agriculture-and-climate-change-comprehensive-analysis|title=East African agriculture and climate change: A comprehensive analysis |date=2013|website=[[International Food Policy Research Institute]] (IFPRI)|language=en|access-date=21 September 2019}}</ref> Projections of climate change are also anticipated to reduce the potential of the cultivated land to produce crops of high quantity and quality.<ref>{{Cite book | vauthors = Kurukulasuriya P, Mendelsohn R |title=How Will Climate Change Shift Agro-Ecological Zones And Impact African Agriculture? |date=25 September 2008|publisher=The World Bank|series=Policy Research Working Papers|doi=10.1596/1813-9450-4717|hdl = 10986/6994|s2cid=129416028 }}</ref>
 
In [[Tanzania]] there is currently no clear signal in future climate projections for rainfall.<ref name=":4">{{Cite web|url=https://futureclimateafrica.org/resource/future-climate-projections-for-tanzania/|title=Future Climate For Africa|website=Brief: future climate projections for Tanzania|publisher=Future Climate For Africa|language=en|access-date=8 August 2019}}</ref> However, there is a higher likelihood of intense future rainfall events.<ref name=":4" />
 
[[Climate change in Kenya]] is expected to have large impacts on the agricultural sector, which is predominantly rain-fed and thus highly vulnerable to changes in temperature and rainfall patterns, and extreme weather events.<ref name=":6">{{Cite web|last=Ministry of Environment and Forestry|title=National Climate Change Action Plan (NCCAP) 2018-2022. Volume I|url=http://www.environment.go.ke/wp-content/uploads/2020/03/NCCAP-2018-2022-v2.pdf}}</ref> Impacts are likely to be particularly pronounced in the arid and semi-arid lands (ASALs) where livestock production is the key economic and livelihood activity. In the ASALs, over 70% of livestock mortality is a result of drought.<ref name=":6" /> Over the next 10 years, 52% of the ASAL cattle population are at risk of loss because of extreme temperature stress.<ref>{{Cite web|last=Kenya Markets Trust|date=2019|title=Contextualising Pathways to Resilience in Kenya's ASALs under the Big Four Agenda|url=https://www.kenyamarkets.org/contextualising-pathways-to-resilience-in-kenyas-asals-under-the-big-four-agenda/}}</ref>
 
==== Southern Africa ====
Climate change will exacerbate the vulnerability of the Agricultural sector in most Southern African countries which are already limited by poor infrastructure and a lag in technological inputs and innovation.<ref>{{cite web |url=https://www.climatelinks.org/sites/default/files/asset/document/2016%20CRM%20Fact%20Sheet%20-%20Southern%20Africa.pdf |title=Fact sheet |website=www.climatelinks.org |access-date=12 July 2020}}</ref> Maize accounts for nearly half of the cultivated land in Southern Africa, and under future climate change, yields could decrease by 30%<ref>{{Cite web|url=http://www.ifpri.org/publication/overview-southern-african-agriculture-and-climate-change|title=Overview [in Southern African Agriculture and Climate Change]|website=www.ifpri.org|access-date=8 August 2019}}</ref> Temperatures increases also encourage a wide spread of weeds and pests<ref>http://cdm15738.contentdm.oclc.org/utils/getfile/collection/p15738coll2/id/127787/filename/127998.pdf</ref> In December 2019, 45 million peoples in southern Africa required help because of crop failure. The drought reduces the water stream in Victoria falls by 50%. The droughts became more frequent in the region.<ref>{{cite news |last1=Rosane |first1=Oivia |title=Victoria Falls Dries Drastically After Worst Drought in a Century |url=https://www.ecowatch.com/victoria-falls-drought-2641553066.htmlOlivia |access-date=11 December 2019 |agency=Ecowatch |date=9 December 2019}}</ref>
 
==== West Africa ====
{{See also|Herder–farmer conflicts in Nigeria}}
Climate change will significantly affect agriculture in West Africa by increasing the variability in food production, access and availability.<ref>https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20090027893.pdf</ref> The region has already experienced a decrease in rainfall along the coasts of Nigeria, Sierra Leone, Guinea and Liberia.<ref>{{cite web |url= http://ebrary.ifpri.org/utils/getfile/collection/p15738coll2/id/127449/filename/127660.pdf|title= Data |website=ebrary.ifpri.org |access-date=12 July 2020}}</ref> This has resulted in lower crop yield, causing farmers to seek new areas for cultivation.<ref>{{Cite web|url=http://www.fao.org/food-chain-crisis/how-we-work/plant-protection/fallarmyworm/en/|title=Fall Armyworm {{!}} FOOD CHAIN CRISIS {{!}} Food and Agriculture Organization of the United Nations|website=www.fao.org|access-date=8 August 2019}}</ref> Staple crops such as maize, rice and sorghum will be impacted by low rainfall events with possible increase in food insecurity.<ref>{{Cite book|date=1997|editor-last=Asenso-Okyere|editor-first=W. K.|editor2-last=Benneh|editor2-first=George|editor3-last=Tims|editor3-first=Wouter | name-list-style = vanc |title=Sustainable Food Security in West Africa|language=en-gb|doi=10.1007/978-1-4615-6105-7|isbn=978-1-4613-7797-9}}</ref>
 
'''Central Africa'''<br />Higher rainfall intensity, prolonged dry spells and high temperatures are expected to negatively impact cassava, maize and bean production in Central Africa.<ref name=":5">{{Cite web|url=https://www.climatelinks.org/file/4614/download?token=rlgPz1eX|title=CLIMATE RISKS IN THE CENTRAL AFRICA REGIONAL PROGRAM FOR THE ENVIRONMENT (CARPE) AND CONGO BASIN|website=Climatelinks}}</ref> Floods and erosion occurrence are expected to damage the already limited transportation infrastructure in the region leading to post harvest losses.<ref name=":5" /> Exportation of economic crops like coffee and cocoa are on the rise within the region but these crops are highly vulnerable to climate change.<ref name=":5" /> Conflicts and political instability have had an impact on agriculture contribution to the regional GDP and this impact will be exacerbated by climatic risks.<ref>{{Cite web|url=https://www.un.org/en/africa/osaa/pdf/pubs/2013africanagricultures.pdf|title=Agriculture in Africa|date=2013|website=United Nations}}</ref>
 
=== Asia ===
In [[East Asia|East]] and [[Southeast Asia]], IPCC (2007:13)<ref name="ar4 summary of regional impacts"/> projected that [[crop yield]]s could increase up to 20% by the mid-21st century. In [[Central Asia|Central]] and South Asia, projections suggested that yields might decrease by up to 30%, over the same time period. These projections were assigned "medium confidence." Taken together, the risk of hunger was projected to remain very high in several developing countries.
 
More detailed analysis of rice yields by the [[International Rice Research Institute]] forecast 20% reduction in yields over the region per degree Celsius of temperature rise. Rice becomes sterile if exposed to temperatures above 35 degrees for more than one hour during flowering and consequently produces no grain.<ref>{{Cite journal|last=Singh|first=Saroj Kumar| name-list-style = vanc |date=2016|title=Climate Change: Impact on Indian Agriculture & its Mitigation|journal=Journal of Basic and Applied Engineering Research|volume=3|issue=10|pages=857–859}}</ref><ref>{{Cite book|url=https://books.google.com/books?id=st52DQAAQBAJ&pg=PA330|title=Reconsidering the Impact of Climate Change on Global Water Supply, Use, and Management|last1=Rao|first1=Prakash|last2=Patil|first2=Yogesh | name-list-style = vanc |publisher=IGI Global|year=2017|isbn=978-1-5225-1047-5|page=330|language=en}}</ref>
 
Global warming of 1.5&nbsp;°C will reduce the ice mass of Asia's high mountains by about 29-43%,<ref>{{Cite journal|last1=Kraaijenbrink|first1=P. D. A.|last2=Bierkens|first2=M. F. P.|last3=Lutz|first3=A. F.|last4=Immerzeel|first4=W. W.|date=September 2017|title=Impact of a global temperature rise of 1.5 degrees Celsius on Asia's glaciers|url=http://www.nature.com/articles/nature23878|journal=Nature|language=en|volume=549|issue=7671|pages=257–260|doi=10.1038/nature23878|pmid=28905897|bibcode=2017Natur.549..257K|s2cid=4398745|issn=0028-0836}}</ref> with impact on water availability and consequently on families and communities that are dependent on glacier- and snow-melt waters for their livelihoods. In the Indus watershed, these mountain water resources contribute to up to 60% of irrigation outside of the monsoon season, and an additional 11% of total crop production.<ref>{{Cite journal|last1=Biemans|first1=H.|last2=Siderius|first2=C.|last3=Lutz|first3=A. F.|last4=Nepal|first4=S.|last5=Ahmad|first5=B.|last6=Hassan|first6=T.|last7=von Bloh|first7=W.|last8=Wijngaard|first8=R. R.|last9=Wester|first9=P.|last10=Shrestha|first10=A. B.|last11=Immerzeel|first11=W. W.|date=July 2019|title=Importance of snow and glacier meltwater for agriculture on the Indo-Gangetic Plain|url=http://www.nature.com/articles/s41893-019-0305-3|journal=Nature Sustainability|language=en|volume=2|issue=7|pages=594–601|doi=10.1038/s41893-019-0305-3|s2cid=199110415|issn=2398-9629}}</ref> In the Ganges basin, the dependency to glacier- and snow-melt is lower but remains critical for irrigation of some crops during the dry season.
 
A 2013 study by the [[International Crops Research Institute for the Semi-Arid Tropics]] ([[ICRISAT]]) aimed to find science-based, pro-poor approaches and techniques that would enable Asia's agricultural systems to cope with climate change, while benefitting poor and vulnerable farmers. The study's recommendations ranged from improving the use of climate information in local planning and strengthening weather-based agro-advisory services, to stimulating diversification of rural household incomes and providing incentives to farmers to adopt natural resource conservation measures to enhance forest cover, replenish groundwater and use [[renewable energy]].<ref>[http://exploreit.icrisat.org/sites/default/files/uploads/1378286859_PolicyBrief23.pdf ''Vulnerability to Climate Change: Adaptation Strategies and layers of Resilience''], [[ICRISAT]], Policy Brief No. 23, February 2013</ref> A 2014 study found that warming had increased maize yields in the [[Heilongjiang]] region of China had increased by between 7 and 17% per decade as a result of rising temperatures.<ref>{{Cite journal | vauthors = Meng Q, Hou P, Lobell DB, Wang H, Cui Z, Zhang F, Chen X | doi = 10.1007/s10584-013-1009-8| title = The benefits of recent warming for maize production in high latitude China| journal = Climatic Change| volume = 122| issue = 1–2| pages = 341–349| year = 2013 | hdl = 10.1007/s10584-013-1009-8| s2cid = 53989985| hdl-access = free}}</ref>
 
A wide range of yield losses due to climate change impacts on wheat, rice, and maize crops in SA is observed. Studies on the effect of warming on crop yield in India reported yield decrease by 5%, 6–8% and 10–30% in wheat,<ref>{{Cite journal|last=Morey, D.|first=D|date=1981|title=Effect of weather elements on yield of wheat at Delhi. PKV Research Journal|journal=PKV Research Journal (Punjabrao Krishi Vidyapeeth), 5, 3.|volume=5,3|via=Punjabrao Krishi Vidyapeeth}}</ref> rice, and maize, respectively . A recent study has shown that such crop-damaging temperatures have led to an increase in the rate of suicides among smallholder farmers in India (Carleton 2017). Nevertheless, lack of crop insurance and the inability to repay loans could be some of the plausible reasons for suicides among farmers.<ref>{{Cite journal|last=Arya|first=Jeetendra Prakash|title=Climate change and agriculture in South Asia: adaptation options in smallholder production systems|url=https://link.springer.com/content/pdf/10.1007/s10668-019-00414-4.pdf|url-status=live|access-date=19 February 2021|journal=Environment, Development and Sustainability|year=2020|volume=22|issue=6|pages=5045–5075|doi=10.1007/s10668-019-00414-4|s2cid=199317833|doi-access=free}} [[File:CC-BY icon.svg|50px]] Text was copied from this source, which is available under a [https://creativecommons.org/licenses/by/4.0/ Creative Commons Attribution 4.0 International License].</ref>
 
Due to climate change, [[livestock]] production will be decreased in [[Bangladesh]] by diseases, scarcity of forage, heat stress and breeding strategies.<ref>{{Cite journal|last=Chowdhury|first=Q M Monzur Kader | name-list-style = vanc |year=2016|title=Impact of Climate Change on Livestock in Bangladesh: A Review of What We Know and What We Need to Know |url=http://ajaset.e-palli.com/wp-content/uploads/2013/12/IMPACT-OF-CLIMATE-CHANGE-ON-LIVESTOCK-IN-BANGLADESH-A-REVIEW-OF-WHAT-WE-KNOW-AND-WHAT-WE-NEED-TO-KNOW.pdf|journal=American Journal of Agricultural Science Engineering and Technology|volume=3 |issue=2|pages=18–25|via=e-palli}}</ref>
 
===Australia and New Zealand===
 
Without further adaptation to climate change, projected impacts would likely be substantial: By 2030, production from agriculture and [[forestry]] was projected to decline over much of southern and eastern Australia, and over parts of eastern New Zealand.<ref name="hennessy australia and new zealand">
{{cite book|title=Climate Change 2007: Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change|vauthors=Hennessy K|publisher=Cambridge University Press|year=2007|veditors=Parry ML|chapter=Chapter 11: Australia and New Zealand: Executive summary|display-authors=etal|display-editors=etal|chapter-url=http://www.ipcc.ch/publications_and_data/ar4/wg2/en/ch11s11-es.html}}
</ref> In New Zealand, initial benefits were projected close to major rivers and in western and southern areas.<ref name="hennessy australia and new zealand" />
 
===Europe===
 
With high confidence, IPCC (2007:14)<ref name="ar4 summary of regional impacts"/> projected that in [[Southern Europe]], climate change would reduce crop productivity. In [[Central Europe|Central]] and [[Eastern Europe]], forest productivity was expected to decline. In [[Northern Europe]], the initial effect of climate change was projected to increase crop yields. The 2019 [[European Environment Agency]] report "Climate change adaptation in the agricultural sector in Europe" again confirmed this. According to this 2019 report, projections indicate that yields of non-irrigated crops like wheat, corn and sugar beet would decrease in southern Europe by up to 50% by 2050 (under a high-end emission scenario). This could result in a substantial decrease in farm income by that date. Also farmland values are projected to decrease in parts of southern Europe by more than 80% by 2100, which could result in land abandonment. The trade patterns are also said to be impacted, in turn affecting agricultural income. Also, increased food demand worldwide could exert pressure on food prices in the coming decades.<ref>{{Cite web|url=https://www.eea.europa.eu/highlights/climate-change-threatens-future-of|title=Climate change threatens future of farming in Europe — European Environment Agency|website=www.eea.europa.eu}}</ref>
 
In 2020, the [[European Union]]'s [[Scientific Advice Mechanism]] published a detailed review of the EU's policies related to the food system, especially the [[Common Agricultural Policy]] and the [[Common Fisheries Policy]], in relation to their sustainability.<ref>{{Cite book|last=Science Advice for Policy by European Academies|url=https://www.sapea.info/wp-content/uploads/sustainable-food-system-review.pdf|title=A sustainable food system for the European Union: A systematic review of the European policy ecosystem|publisher=SAPEA|year=2020|isbn=978-3-9820301-7-3|location=Berlin|doi=10.26356/sustainablefoodreview}}</ref>
 
===Latin America===
 
The major agricultural products of [[Latin American]] regions include [[livestock]] and grains, such as [[maize]], [[wheat]], [[soybeans]], and [[rice]].<ref name="ref 1">{{cite journal| vauthors = Jones P, Thornton P|title=The potential impacts of climate change on maize production in Africa and Latin America in 2055|journal=Global Environmental Change|date=April 2003|volume=13|issue=1|pages=51–59|doi=10.1016/S0959-3780(02)00090-0}}</ref><ref name="ref 2" /> Increased temperatures and altered hydrological cycles are predicted to translate to shorter growing seasons, overall reduced biomass production, and lower grain yields.<ref name="ref 2">{{cite journal| vauthors = Baethgen WE |title=Vulnerability of the agricultural sector of Latin America to climate change|journal=Climate Research|date=1997|volume=9|pages=1–7|doi=10.3354/cr009001|bibcode=1997ClRes...9....1B|url=https://www.int-res.com/articles/cr/9/c009p001.pdf|doi-access=free}}</ref><ref name="ref 3">{{cite journal| vauthors = Mendelsohn R, Dinar A |title=Climate Change, Agriculture, and Developing Countries: Does Adaptation Matter?|journal=The World Bank Research Observer|date=1 August 1999|volume=14|issue=2|pages=277–293|doi=10.1093/wbro/14.2.277}}</ref> [[Brazil]], [[Mexico]] and [[Argentina]] alone contribute 70-90% of the total agricultural production in Latin America.<ref name="ref 2"/> In these and other dry regions, maize production is expected to decrease.<ref name="ref 1"/><ref name="ref 2"/> A study summarizing a number of impact studies of climate change on agriculture in Latin America indicated that wheat is expected to decrease in Brazil, Argentina and [[Uruguay]].<ref name="ref 2"/> Livestock, which is the main agricultural product for parts of Argentina, Uruguay, southern Brazil, [[Venezuela]], and [[Colombia]] is likely to be reduced.<ref name="ref 1"/><ref name="ref 2"/> Variability in the degree of production decrease among different regions of Latin America is likely.<ref name="ref 1"/> For example, one 2003 study that estimated future maize production in Latin America predicted that by 2055 maize in eastern Brazil will have moderate changes while Venezuela is expected to have drastic decreases.<ref name="ref 1" />
 
Increased rainfall variability has been one of the most devastating consequences of climate change in Central America and Mexico. From 2009 to 2019, the region saw years of heavy rainfall in between years of below average rainfall.<ref name=":8">{{Cite news|date=22 February 2019|title=What's Really Driving Immigrants North from Central America|work=The State of Things|type=Podcast|url=https://www.wunc.org/show/the-state-of-things/2019-02-22/whats-really-driving-immigrants-north-from-central-america|access-date=1 June 2021}}</ref> The spring rains of May and June have been particularly erratic, posing issues for farmers plant their maize crops at the onset of the spring rains. Most subsistence farmers in the region have no irrigation and thus depend on the rains for their crops to grow. In Mexico, only 21% of farms are irrigated, leaving the remaining 79% dependent on rainfall.<ref name=":9">{{Cite journal|last1=Green|first1=Lisa|last2=Schmook|first2=Birgit|last3=Radel|first3=Claudia|last4=Mardero|first4=Sofia|date=March 2020|title=Living Smallholder Vulnerability: The Everyday Experience of Climate Change in Calakmul, Mexico|url=https://doi.org/10.1353/lag.2020.0028|journal=Journal of Latin American Geography|publisher=University of Texas Press|volume=19|issue=2|pages=110–142|doi=10.1353/lag.2020.0028}}</ref>
 
Suggested potential adaptation strategies to mitigate the impacts of global warming on agriculture in Latin America include using plant breeding technologies and installing irrigation infrastructure.<ref name="ref 2" />
 
==== Climate justice and subsistence farmers ====
 
Several studies that investigated the impacts of climate change on agriculture in Latin America suggest that in the poorer countries of [[Latin America]], agriculture composes the most important economic sector and the primary form of sustenance for small farmers.<ref name="ref 1"/><ref name="ref 2"/><ref name="ref 3"/><ref name="ref 4">{{cite journal | vauthors = Morton JF | title = The impact of climate change on smallholder and subsistence agriculture | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 104 | issue = 50 | pages = 19680–5 | date = December 2007 | pmid = 18077400 | pmc = 2148357 | doi = 10.1073/pnas.0701855104 | doi-access = free }}</ref> [[Maize]] is the only grain still produced as a sustenance crop on small farms in Latin American nations.<ref name="ref 2"/> Scholars argue that the projected decrease of this grain and other crops will threaten the welfare and the economic development of subsistence communities in Latin America.<ref name="ref 1"/><ref name="ref 2"/><ref name="ref 3"/> Food security is of particular concern to rural areas that have weak or non-existent food markets to rely on in the case food shortages.<ref name="ref 5">{{cite journal |last1=Timmons Roberts |first1=J. |title=The International Dimension of Climate Justice and the Need for International Adaptation Funding |journal=Environmental Justice |date=December 2009 |volume=2 |issue=4 |pages=185–190 |doi=10.1089/env.2009.0029 }}</ref> In August 2019, Honduras declared a state of emergency when a drought caused the southern part of the country to lose 72% of its corn and 75% of its beans. Food security issues are expected to worsen across Central America due to climate change. It is predicted that by 2070, corn yields in Central America may fall by 10%, beans by 29%, and rice by 14%. With Central American crop consumption dominated by corn (70%), beans (25%), and rice (6%), the expected drop in staple crop yields could have devastating consequences.<ref>{{Cite news|last=Masters|first=Jeff|date=23 December 2019|title=Fifth Straight Year of Central American Drought Helping Drive Migration|work=Scientific American|url=https://blogs.scientificamerican.com/eye-of-the-storm/fifth-straight-year-of-central-american-drought-helping-drive-migration/|access-date=1 June 2021}}</ref>
 
According to scholars who considered the environmental justice implications of climate change, the expected impacts of climate change on subsistence farmers in Latin America and other developing regions are unjust for two reasons.<ref name="ref 4"/><ref name="ref 6">{{cite journal |last1=Davies |first1=Mark |last2=Guenther |first2=Bruce |last3=Leavy |first3=Jennifer |last4=Mitchell |first4=Tom |last5=Tanner |first5=Thomas | name-list-style = vanc |title=Climate Change Adaptation, Disaster Risk Reduction and Social Protection: Complementary Roles in Agriculture and Rural Growth? |journal=IDS Working Papers |date=February 2009 |volume=2009 |issue=320 |pages=01–37 |doi=10.1111/j.2040-0209.2009.00320_2.x |url=http://opendocs.ids.ac.uk/opendocs/handle/123456789/2545 }}</ref> First, subsistence farmers in developing countries, including those in Latin America are disproportionately vulnerable to climate change<ref name="ref 6"/> Second, these nations were the least responsible for causing the problem of anthropogenic induced climate.<ref name="ref 6" />{{Better source needed|date=December 2021|reason=Brazil emitted a lot since the source was published}}
 
According to researchers John F. Morton and T. Roberts, disproportionate vulnerability to climate disasters is socially determined.<ref name="ref 4"/><ref name="ref 6"/> For example, socioeconomic and policy trends affecting smallholder and subsistence farmers limit their capacity to adapt to change.<ref name="ref 4"/> According to W. Baethgen who studied the vulnerability of Latin American agriculture to climate change, a history of policies and economic dynamics has negatively impacted rural farmers.<ref name="ref 2"/> During the 1950s and through the 1980s, high inflation and appreciated real exchange rates reduced the value of agricultural exports.<ref name="ref 2"/> As a result, farmers in Latin America received lower prices for their products compared to world market prices.<ref name="ref 2"/> Following these outcomes, Latin American policies and national crop programs aimed to stimulate agricultural intensification.<ref name="ref 2"/> These national crop programs benefitted larger commercial farmers more. In the 1980s and 1990s low world market prices for cereals and livestock resulted in decreased agricultural growth and increased rural poverty.<ref name="ref 2"/>
 
Perceived vulnerability to climate change differs even within communities. In a study of subsistence farmers in Calakmul, Mexico, authors found that ''pobladores'' (community members without land rights but who can work on communal land) felt more susceptible to climate change than ''ejidatarios'' (ones who hold land in the communal land system). ''Pobladores'' usually farm on the poorest quality land that may not have access to streams to use during a drought or highlands to use during a flood. Furthermore, pobladores have reduced access to state funds for climate change mitigation aid since they have to ask the ''ejidal'' leadership for approval before applying for state funds. Nearly every ''poblador'' interviewed said they had experienced hunger within 2013 - 2016, while only 25% of ''ejidatarios'' said they had felt hunger in that timeframe.<ref name=":9" />
 
In the book, Fairness in Adaptation to Climate Change, the authors describe the global injustice of climate change between the rich nations of the north, who are the most responsible for global warming and the southern poor countries and minority populations within those countries who are most vulnerable to climate change impacts.<ref name="ref 6"/>
 
Adaptive planning is challenged by the difficulty of predicting local scale climate change impacts.<ref name="ref 4"/> An expert that considered opportunities for climate change adaptation for rural communities argues that a crucial component to adaptation should include government efforts to lessen the effects of food shortages and famines.<ref name="ref 7">{{cite book |editor-last=Adger |editor-first=Neil |editor-link=Neil Adger |editor2=Jouni Paavola |editor3=Saleemul Huq |display-editors=etal |title=Fairness in adaptation to climate change |date=2006 |publisher=MIT Press |location=Cambridge, MA |isbn=978-0-262-01227-0}}</ref> This researcher also claims that planning for equitable adaptation and agricultural sustainability will require the engagement of farmers in decision making processes.<ref name="ref 7"/>
 
===North America===
{{See also|Climate change and agriculture in the United States}}
A number of studies have been produced which assess the impacts of climate change on agriculture in [[North America]]. The IPCC Fourth Assessment Report of agricultural impacts in the region cites 26 different studies.<ref>{{cite book | vauthors=Field CB | contribution=Sec. 14.4.4 Agriculture, forestry and fisheries | title=Chapter 14: North America | series=Climate change 2007: impacts, adaptation and vulnerability: contribution of Working Group II to the fourth assessment report of the Intergovernmental Panel on Climate Change | url=http://www.ipcc.ch/publications_and_data/ar4/wg2/en/ch14s14-4-4.html | veditors=Parry ML | year=2007 | publisher=Cambridge University Press | isbn=978-0-521-88010-7 | display-authors=etal | access-date=5 February 2013 | archive-url=https://web.archive.org/web/20130310060529/http://www.ipcc.ch/publications_and_data/ar4/wg2/en/ch14s14-4-4.html | archive-date=10 March 2013 | url-status=dead }}</ref> With high confidence, IPCC (2007:14–15)<ref name="ar4 summary of regional impacts"/> projected that over the first few decades of this century, moderate climate change would increase aggregate yields of rain-fed agriculture by 5–20%, but with important variability among regions. Major challenges were projected for crops that are near the warm end of their suitable range or which depend on highly utilized water resources.
 
Droughts are becoming more frequent and intense in arid and [[semiarid]] western North America as temperatures have been rising, advancing the timing and magnitude of spring snow melt floods and reducing river flow volume in summer.<ref>{{cite web|url=http://www.ncdc.noaa.gov/billions/events|title=Billion-Dollar Weather and Climate Disasters: Table of Events - National Centers for Environmental Information (NCEI)|first=Adam|last=Smith | name-list-style = vanc }}</ref> Direct effects of climate change include increased heat and water stress, altered crop [[phenology]], and disrupted symbiotic interactions. These effects may be exacerbated by climate changes in river flow, and the combined effects are likely to reduce the abundance of native trees in favour of non-native [[herbaceous]] and drought-tolerant competitors, reduce the habitat quality for many native animals, and slow litter decomposition and [[nutrient]] cycling. Climate change effects on human water demand and irrigation may intensify these effects.<ref>{{cite journal|last1= Perry|first1= Laura G.|last2= Andersen|first2= Douglas C.|last3= Reynolds|first3= Lindsay V.|last4= Nelson|first4= S. Mark|last5= Shafroth|first5= Patrick B. | name-list-style = vanc |year=2012 |title=Vulnerability of riparian ecosystems to elevated CO2 and climate change in arid and semiarid western North America |url=http://www.fort.usgs.gov/Products/Publications/23228/23228.pdf |journal=Global Change Biology |volume=18 |issue=3 |pages=821–842 |doi=10.1111/j.1365-2486.2011.02588.x |url-status=dead |archive-url=https://web.archive.org/web/20130526135544/http://www.fort.usgs.gov/Products/Publications/23228/23228.pdf |archive-date=26 May 2013|bibcode= 2012GCBio..18..821P}}</ref>
 
The US Global Change Research Program (2009) assessed the literature on the impacts of climate change on agriculture in the United States, finding that many crops will benefit from increased atmospheric {{CO2}} concentrations and low levels of warming, but that higher levels of warming will negatively affect growth and yields; that extreme weather events will likely reduce crop yields; that [[weed]]s, [[disease]]s and [[insect]] [[pest (organism)|pests]] will benefit from warming, and will require additional [[pest control|pest]] and [[weed control]]; and that increasing {{CO2}} concentrations will reduce the land's ability to supply adequate livestock feed, while increased heat, disease, and weather extremes will likely reduce livestock productivity.<ref>{{cite book | author=USGCRP | year=2009 | title=Global Climate Change Impacts in the United States | chapter=Agriculture | veditors = Karl TR, Melillo J, Peterson T, Hassol SJ | publisher=Cambridge University Press | isbn=978-0-521-14407-0 | url=http://www.globalchange.gov/publications/reports/scientific-assessments/us-impacts | chapter-url=http://www.globalchange.gov/publications/reports/scientific-assessments/us-impacts/climate-change-impacts-by-sector/agriculture}}</ref>
 
===Polar regions===
 
For the [[polar region]] ([[Arctic]] and [[Antarctica]]), the benefits of a less severe climate are dependent on local conditions: One of these benefits was judged to be increased agricultural and forestry opportunities.<ref>{{cite book|title=Climate Change 2007: Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change|vauthors=Anisimov OA|publisher=Cambridge University Press|year=2007|editor=Parry, ML|chapter=Chapter 15: Polar regions (Arctic and Antarctic): Executive summary|display-authors=etal|display-editors=etal|chapter-url=http://www.ipcc.ch/publications_and_data/ar4/wg2/en/ch15s15-es.html}}</ref>
 
Climate change has affected agriculture in Iceland: Rising temperatures had made the widespread sowing of [[barley]] possible, which had been untenable twenty years ago. Some of the warming was due to a local (possibly temporary) effect via ocean currents from the Caribbean, which had also affected fish stocks.<ref>{{cite news |url=https://www.theguardian.com/climatechange/story/0,12374,1517939,00.html |title=Frozen assets |first=Paul |last=Brown | name-list-style = vanc |work=The Guardian |date=30 June 2005 |access-date=22 January 2008}}</ref>
 
===Small islands===
 
{{see also|Alliance of Small Island States}}
 
In a literature assessment, Mimura et al. (2007:689)<ref>
{{cite book | year = 2007 | chapter = Chapter 16: Small islands: Executive summary | title = Climate Change 2007: Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change | veditors = Parry ML | display-editors = etal | publisher = Cambridge University Press | vauthors = Mimura N | chapter-url = http://www.ipcc.ch/publications_and_data/ar4/wg2/en/ch16s16-es.html | display-authors = etal }}
</ref> concluded that on small islands, [[subsistence agriculture|subsistence]] and [[commercial agriculture]] would very likely be adversely affected by climate change. This projection was assigned "high confidence."
 
== Mitigation and adaptation==
{{externalvideo|video1=[https://www.youtube.com/watch?v=gWORvA_p9i0&t=870s Agriculture, Population Growth, and the Challenge of Climate Change: Santa Cruz Emeriti group]}}
{{main|Climate change mitigation|Climate change adaptation}}
 
=== In developed countries ===
Agriculture is often not included in government emissions reductions plans.<ref>{{Cite web|date=3 December 2014|title=Livestock – Climate Change's Forgotten Sector: Global Public Opinion on Meat and Dairy Consumption|url=https://www.chathamhouse.org/2014/12/livestock-climate-changes-forgotten-sector-global-public-opinion-meat-and-dairy-consumption|access-date=6 June 2021|website=www.chathamhouse.org|language=en}}</ref> For example, the agricultural sector is exempt from the [[European Union Emission Trading Scheme|EU emissions trading scheme]]<ref>{{Cite web|last=Barbière|first=Cécile|date=12 March 2020|title=Europe's agricultural sector struggles to reduce emissions|url=https://www.euractiv.com/section/climate-environment/news/europes-agricultural-sector-struggles-to-reduce-emissions/|access-date=6 June 2021|website=www.euractiv.com|language=en-GB}}</ref> which covers around 40% of the EU greenhouse gas emissions.<ref>{{Cite web|last=Anonymous|date=23 November 2016|title=EU Emissions Trading System (EU ETS)|url=https://ec.europa.eu/clima/policies/ets_en|access-date=6 June 2021|website=Climate Action - European Commission|language=en}}</ref>
 
Several mitigation measures for use in developed countries have been proposed:
<ref>{{Cite web|url=https://cgspace.cgiar.org/bitstream/handle/10568/71051/SBSTA44-Agricultural-practices-technologies.pdf|title=Climate change adaptation in agriculture: practices and technologies}}</ref>
* breeding more resilient crop varieties, and diversification of crop species
* using improved agroforestry species
* capture and retention of rainfall, and use of improved irrigation practices
* Increasing forest cover and [[Agroforestry]]
* use of emerging water harvesting techniques (such as [[contour trenching]], ...)
 
=== In developing countries ===
The [[Intergovernmental Panel on Climate Change]] ([[IPCC]]) has reported that agriculture is responsible for over a quarter of total global greenhouse gas emissions.<ref name="IPCC">[[IPCC]]. 2007. Climate Change 2007: Synthesis Report. Contributions of Working Groups I, Ii, and Iiito the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. Geneva:
IPCC</ref> Given that agriculture's share in global [[gross domestic product]] (GDP) is about 4%, these figures suggest that agricultural activities produce high levels of [[greenhouse gas]]es. Innovative agricultural practices and technologies can play a role in [[climate]] change mitigation<ref name="mitigation">Basak R. 2016. Benefits and costs of climate change mitigation technologies in paddy rice: Focus on Bangladesh and Vietnam. CCAFS Working Paper no. 160. Copenhagen, Denmark: CGIAR Research Program on Climate Change, Agriculture and Food Security (CCAFS). https://cgspace.cgiar.org/rest/bitstreams/79059/retrieve</ref> and [[Ecosystem-based adaptation|adaptation]]. This adaptation and mitigation potential is nowhere more pronounced than in developing countries where agricultural productivity remains low; poverty, vulnerability and food insecurity remain high; and the direct effects of climate change are expected to be especially harsh. Creating the necessary agricultural technologies and harnessing them to enable developing countries to adapt their agricultural systems to changing climate will require innovations in policy and institutions as well. In this context, institutions and policies are important at multiple scales.
 
Travis Lybbert and [[Daniel A. Sumner|Daniel Sumner]] suggest six policy principles:<ref>{{cite journal |last1=Lybbert |first1=Travis J. |last2=Sumner |first2=Daniel A. | name-list-style = vanc |title=Agricultural technologies for climate change in developing countries: Policy options for innovation and technology diffusion |journal=Food Policy |date=February 2012 |volume=37 |issue=1 |pages=114–123 |doi=10.1016/j.foodpol.2011.11.001 }}</ref>
#The best policy and institutional responses will enhance information flows, incentives and flexibility.
#Policies and institutions that promote economic development and reduce poverty will often improve agricultural adaptation and may also pave the way for more effective climate change mitigation through agriculture.
#Business as usual among the world's poor is not adequate.
#Existing technology options must be made more available and accessible without overlooking complementary capacity and investments.
#Adaptation and mitigation in [[agriculture]] will require local responses, but effective policy responses must also reflect global impacts and inter-linkages.
#[[Trade]] will play a critical role in both mitigation and adaptation, but will itself be shaped importantly by climate change.
 
State- or NGO-sponsored projects can help farmers be more resilient to climate change, such as irrigation infrastructure providing a dependable water source as rains become more erratic.<ref>{{Cite news|last=Wernick|first=Adam|date=6 February 2019|title=Climate change is the overlooked driver of Central American migration|work=The World|type=Podcast|url=https://www.pri.org/stories/2019-02-06/climate-change-overlooked-driver-central-american-migration|access-date=31 May 2021}}</ref><ref name=":9" /> Water catchment systems that collect water during the rainy season to be used during the dry season or periods of drought, can also be used to mitigate the effects of climate change.<ref name=":9" /> Some programs, like Asociación de Cooperación para el Desarrollo Rural de Occidente (C.D.R.O.), a Guatemalan program funded by the United States’ government until 2017, focus on agroforestry and weather monitoring systems to help farmers adapt. The organization provided residents with resources to plant new, more adaptable crops to alongside their typical maize to protect the corn from variable temperatures, frost, etc. C.D.R.O. also set up a weather monitoring system to help predict extreme weather events, and would send residents text messages to warn them about periods of frosts, extreme heat, humidity, or drought.<ref>{{Cite news|last=Blitzer|first=Jonathan|date=3 April 2019|title=How Climate Change is Fuelling the U.S. Border Crisis|work=The New Yorker|url=https://www.newyorker.com/news/dispatch/how-climate-change-is-fuelling-the-us-border-crisis|access-date=1 June 2021}}</ref> Projects focusing on irrigation, water catchment, agroforestry, and weather monitoring can help Central American residents adapt to climate change.
 
The Agricultural Model Intercomparison and Improvement Project (AgMIP)<ref>{{cite press release |url=https://www.worldscientific.com/page/pressroom/2015-03-10-02 |title=Food for the Future - Assessments of Impacts of Climate Change on Agriculture |publisher=Imperial College Press |date=April 2015 |access-date=17 July 2019 }}</ref> was developed in 2010 to evaluate agricultural models and intercompare their ability to predict climate impacts. In sub-Saharan Africa and South Asia, South America and East Asia, AgMIP regional research teams (RRTs) are conducting integrated assessments to improve understanding of agricultural impacts of climate change (including biophysical and [[economic impacts of climate change|economic impacts]]) at national and regional scales. Other AgMIP initiatives include global gridded modeling, data and information technology (IT) tool development, simulation of crop pests and diseases, site-based crop-climate sensitivity studies, and aggregation and scaling.
 
One of the most important projects to mitigate climate change with agriculture and adapting agriculture to climate change at the same time, was launched in 2019 by the "Global EverGreening Alliance". The initiative was announced in the [[2019 UN Climate Action Summit]]. One of the main methods is [[Agroforestry]]. Another important method is [[Conservation farming]]. One of the targets is to [[Carbon sequestration|sequester carbon]] from the atmosphere. By 2050 the restored land should sequestrate 20 billion of carbon annually. The coalition wants, among other, to recover with trees a territory of 5.75 million square kilometres, achieve a health tree - grass balance on a territory of 6.5 million square kilometres and increase carbon capture in a territory of 5 million square kilometres.
 
The first phase is the "Grand African Savannah Green Up" project. Already millions families implemented these methods, and the average territory covered with trees in the farms in [[Sahel]] increased to 16%.<ref>{{cite news |last1=Hoffner |first1=Erik |title=Grand African Savannah Green Up': Major $85 Million Project Announced to Scale up Agroforestry in Africa |url=https://www.ecowatch.com/agroforestry-africa-climate-summit-2641102482.html |access-date=27 October 2019 |agency=Ecowatch |date=25 October 2019}}</ref>
 
=== Climate-smart agriculture ===
{{Excerpt|Climate-smart agriculture}}
 
=== Policies for climate change mitigation ===
{{#section-h:Sustainable food system|Public policy}}
 
=== Policies for climate change adaptation ===
{{#section-h:Climate change adaptation|Agricultural production}}
 
== See also ==
{{Portal|Global warming|Environment|Energy}}
{{Div col|small=yes}}
* [[Agroecology]]
* [[Aridification]]
* [[Biochar]]
* [[Climate change and invasive species]]
* [[Climate change and meat production]]
* [[Climate resilience]]
* [[Effects of climate change on humans]]
* [[Environmental issues with agriculture]]
* [[Fisheries and Climate Change]]
* [[Food security]]
* [[Global warming and wine]]
* [[International Assessment of Agricultural Science and Technology for Development]] addressing the links between climate change & agriculture
* [[Land Allocation Decision Support System]] – a research tool that is used to test how climate change may affect agriculture (e.g. yield and quality)
* [[Slash-and-char]]
* [[Terra preta]]
{{Div col end}}
 
== References ==
{{Reflist}}
 
== External links ==
* [http://www.fao.org/climatechange/en/ Climate change] on the [[Food and Agriculture Organization]] of the United Nations website.
* [http://www.ifpri.org/publication/climate-change-1 Report on the relationship between climate change, agriculture and food security] by the [[International Food Policy Research Institute]]
* [http://www.adb.org/features/12-things-know-2012-rice Climate Change, Rice and Asian Agriculture: 12 Things to Know] Asian Development Bank
*"[https://farmingfirst.org/climate_infographic/ A History of Agriculture and Climate Change at the UNFCCC]" infographic
* [http://www.ccafs.cgiar.org/ Climate Change, Agriculture and Food Security] ([[Consultative Group on International Agricultural Research]])
 
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{{agriculture footer}}
 
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