Climate change and agriculture 61910 226134211 2008-07-16T23:40:06Z 220.233.21.169 /* External links */ [[Climate change]] and [[agriculture]] are interrelated processes, both of which take place on a global scale.<ref>[http://www.grida.no/climate/ipcc/emission/076.htm Intergovermental Panel on Climate Change Special Report on Emissions Scenarios] retrieved 26 Jun 2007</ref> [[Global warming]] is projected to have significant impacts on conditions affecting agriculture, including [[temperature]], [[Precipitation (meteorology)|precipitation]] and glacial run-off. These conditions determine the [[carrying capacity]] of the [[biosphere]] to produce enough [[food]] for the [[human population]] and domesticated animals. Rising [[carbon dioxide]] levels would also have effects, both detrimental and beneficial, on crop yields. The overall effect of climate change on agriculture will depend on the balance of these effects. Assessment of the effects of global climate changes on agriculture might help to properly anticipate and adapt farming to maximize [[agriculture|agricultural production]]. [[Image:Greenhouse Gas by Sector.png|thumb|350px|right]] At the same time, agriculture has been shown to produce significant effects on climate change, primarily through the production and release of [[greenhouse gases]] such as [[carbon dioxide]], [[methane]], and [[nitrous oxide]], but also by altering the earth's [[land cover]], which can change its ability to absorb or reflect heat and light, thus contributing to [[radiative forcing]]. [[Land use]] change such as [[deforestation]] and [[desertification]], together with use of [[fossil fuel]]s, are the major [[anthropogenic]] sources of carbon dioxide; agriculture itself is the major contributor to increasing methane and nitrous oxide concentrations in earth's [[atmosphere]].<ref>[http://www.ipcc.ch/SPM2feb07.pdf UN Report on Climate Change] retrieved 25 Jun 2007</ref> == Impact of climate change on agriculture == {{refimprove| section|date=July 2007}} Despite technological advances, such as [[crop breeding|improved varieties]], [[GMO|genetically modified organisms]], and [[irrigation]] systems, [[weather]] is still a key factor in agricultural productivity, as well as [[soil]] properties and [[biota|natural communities]]. The effect of climate on agriculture is related to variabilities in local climates rather than in global climate patterns. Consequently, [[agronomist]]s consider any assessment has to be individually consider each [[ecoregion|local area]]. On the other hand, [[agricultural economics|agricultural trade]] has grown in recent years, and now provides significant amounts of [[food]], on a national level to major importing countries, as well as comfortable [[gross domestic product|income]] to exporting ones. The international aspect of trade and security in terms of food implies the need to also consider the effects of [[global climate change|climate change]] on a global scale. A study published in ''[[Science (journal)|Science]]'' suggest that, due to climate change, "southern Africa could lose more than 30% of its main crop, maize, by 2030. In South Asia losses of many regional staples, such as rice, millet and maize could top 10%".<ref>{{cite news | url=http://news.bbc.co.uk/2/hi/science/nature/7220807.stm | title=Climate 'could devastate crops' | date=[[31 January]] [[2008]] | publisher=[[BBC News Online]]}}</ref><ref>{{cite journal |author=Lobell DB, Burke MB, Tebaldi C, Mastrandrea MD, Falcon WP, Naylor RL |title=Prioritizing climate change adaptation needs for food security in 2030 |journal=Science |volume=319 |issue=5863 |pages=607–10 |year=2008 |pmid=18239122 |doi=10.1126/science.1152339}}</ref> The 2001 [[IPCC]] [[IPCC Third Assessment Report|Third Assessment Report]] 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 fishing industry will also be severely affected in some places. 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 [[UKMO]] scenario whereas corn production in Europe is expected to grow up to 25% in optimum [[hydrologic]] conditions. More favourable effects on yield tend to depend to a large extent on realization of the potentially 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]] 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 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]] 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. ==== Shortage in grain production ==== [[Image:Sunflower crop on the Darling Downs, Queensland.jpg|thumb|right|Crops such as these [[sunflower]]s can be affected by severe [[drought]] conditions in [[Australia]].<ref>[http://www.lilith-ezine.com/articles/environmental/Australian-Drought.html Australian Drought and Climate Change], retrieved on June 7th 2007.</ref>]] Between 1996 and 2003, [[cereal|grain]] [[Production, costs, and pricing|production]] has stabilized slightly over 1800 millions of [[ton]]s. In 2000, 2001, 2002 and 2003, grain stocks have been dropping, resulting in a global grain [[harvest]] that was short of [[Consumption (economics)|consumption]] by 93 millions of tons in 2003. The earth's average temperature has been rising since the late 1970s, with nine of the 10 warmest years on record occurring since 1995<ref>{{cite pressrelease | title=NOAA reports 2005 global temperature similar to 1998 record warm year | url=http://www.publicaffairs.noaa.gov/releases2006/jan06/noaa06-013.html | publisher=[[NOAA]] | date=[[2006-01-30]] | accessdate=2007-07-26 }}</ref>. In 2002, [[India]] and the [[United States]] suffered sharp harvest reductions because of record temperatures and [[drought]]. In 2003 [[Europe]] suffered very low [[rainfall]] throughout spring and summer, and a record level of heat damaged most [[agriculture|crops]] from the [[United Kingdom]] and [[France]] in the [[Western Europe]] through [[Ukraine]] in the [[Eastern Europe|East]]. [[Bread]] [[price]]s have been rising in several countries in the region. (see [[w:fr:canicule 2003]]). ==== Poverty impacts ==== 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]]. 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">{{cite web |url=http://www.odi.org.uk/nrp/NRP109.pdf |title= Climate change, agricultural policy and poverty reduction – how much do we know? |accessyear=2007 |year=2007 |publisher=[[Overseas Development Institute]]}}</ref> ==== 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 [[weed]]s, [[disease]] and insect [[pest (animal)|pest]]s 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, [[temperature]]s raise ranging from 1[[Celsius|°C]] up to 5°C, and with [[rainfall]] levels an increase or decrease of 20%. Other parameters may include [[humidity]], [[wind]], and [[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]]. ==== Temperature potential effect on growing period ==== Duration of crop [[cell growth|growth]] [[biological life cycle|cycle]]s are above all, related to temperature. An increase in temperature will speed up development. 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. ==== Potential effect of atmospheric carbon dioxide on yield ==== [[Carbon dioxide]] is essential to plant growth. Rising CO<sub>2</sub> concentration in the atmosphere can have both positive and negative consequences. Increased CO<sub>2</sub> is expected to have positive physiological effects by increasing the rate of [[photosynthesis]]. Currently, the amount of carbon dioxide in the atmosphere is 380 [[parts per million]]. In comparison, the amount of [[oxygen]] is 210,000 ppm. This means that often plants may be starved of carbon dioxide, being outnumbered by the photosynthetic pollutant oxygen. The effects of an increase in carbon dioxide would be higher on [[C3 plants|C3 crops]] (such as [[wheat]]) than on [[C4 plants|C4 crops]] (such as [[maize]]), because the former is more susceptible to carbon dioxide shortage. Under optimum conditions of temperature and humidity, the yield increase could reach 36%, if the levels of carbon dioxide are doubled.{{Fact|date=February 2007}} However, other studies also show a change in harvest quality. The growth improvement in [[C3 plants]] could favor vegetative [[biomass]] on grain biomass; thus leading to a decrease in grain production yield. Further, few studies have looked at the impact of elevated carbon dioxide concentrations on whole farming systems. Most models study the relationship between CO<sub>2</sub> and productivity in isolation from other factors associated with climate change, such as an increased frequency of extreme weather events, seasonal shifts, and so on. Moreover, it is reasonable to expect that weed productivity will increase in parallel with that of crop and pasture plants; potentially raising the cost of defensive expenditures like herbicides. In 2005, the Royal Society in London concluded that the purported benefits of CO<sub>2</sub> fertilization are “likely to be far lower than previously estimated” when factors such as increasing ground-level ozone are taken into account." <ref> Royal Society (2005) Impact of climate change on crops worse than previously thought http://royalsociety.org/news.asp?id=3084 </ref> ==== Effect on quality ==== According to the IPCC's TAR, "The importance of climate change impacts on grain and forage quality emerges from new research. 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] IPCC</ref> Studies have 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>[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>[http://www.math.unl.edu/~iloladze/NewSci/NewSci.htm Plague of plenty] New Scientist Archive</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>[http://www.grist.org/news/maindish/2005/07/12/scherer-plantchem/ The Food, the Bad, and the Ugly] ''Scherer, Glenn'' Grist July, 2005</ref> ==== Agricultural surfaces and climate changes ==== Climate change is likely to increase the amount of [[arable land]] in high-lattitude region by reduction of the amount of frozen lands. A 2005 study reports that temperature in siberia has increased three degree celcius 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 an northward extension of farmable lands,<ref>The Danger of Climate Change for Russia – Expected Losses and Recommendations, By Alexey O. Kokorin and Inna G. Gritsevich, Moscow, russian analytical digest 23/07 [http://se2.isn.ch/serviceengine/FileContent?serviceID=ISFPub&fileid=E97C8CEF-87D1-D8C6-53EA-0991B4B6BA3B&lng=en]</ref> they also warn of possible productivity losses and increased risk of drought.<ref>Global warming 'will hurt Russia', 14:23 03 October 2003, NewScientist.com news service </ref> [[Sea level]]s 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 loss, in particular in areas such as [[South East Asia]]. [[Erosion]], [[sea level rise|submergence of shoreline]]s, [[salinity]] of the [[water table]] due to the increased sea levels, could mainly affect agriculture through [[inundation]] of [[depression (geology)|low-lying lands]]. ==== Erosion and fertility ==== With global warming, [[Soils retrogression and degradation|soil degradation]] is more likely to occur, and soil [[fertility]] would probably be affected by global warming. However, because the ratio of carbon to nitrogen is a [[constant]], a doubling of carbon is likely to imply a higher storage of [[nitrogen]] in soils as [[nitrate]]s, thus providing higher fertilizing elements for plants, providing better yields. The average needs for nitrogen could decrease, and give the opportunity of changing often 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. ==== Potential effects of global climate change on pests, diseases and weeds ==== A very important point to consider is that [[weed]]s 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 gain in effectiveness with the temperature increase.{{Fact|date=April 2007}} 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 favor the development of [[fungi|fungal]] diseases. Similarly, because of higher temperatures and humidity, there could be an increased pressure from [[insect]]s and disease [[vector (biology)|vector]]s. ==== Glacier retreat and disappearance ==== The continued [[Effects of global warming#Glacier retreat and disappearance|retreat of glaciers]] will have a number of different quantitative impacts. In 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. According to a UN climate report, the [[Himalayas|Himalayan]] glaciers that are the principal dry-season water sources of [[Asia]]'s biggest rivers - [[Ganges]], [[Indus]], [[Brahmaputra]], [[Yangtze]], [[Mekong]], [[Salween]] and [[Yellow river|Yellow]] - could disappear by 2035 as temperatures rise.<ref>[http://www.planetark.com/dailynewsstory.cfm/newsid/42387/story.htm Vanishing Himalayan Glaciers Threaten a Billion]</ref> Approximately 2.4 billion people live in the [[drainage basin]] of the Himalayan rivers.<ref>[http://www.peopleandplanet.net/pdoc.php?id=3024 Big melt threatens millions, says UN]</ref> [[India]], [[China]], [[Pakistan]], [[Afghanistan]], [[Bangladesh]], [[Nepal]] and [[Myanmar]] could experience floods followed by severe [[drought]]s in coming decades.<ref>[http://english.peopledaily.com.cn/90001/90781/90879/6222327.html Glaciers melting at alarming speed]</ref> In [[India]] alone, the Ganges provides water for drinking and farming for more than 500 million people.<ref>[http://www.rediff.com/news/2007/jul/24indus.htm Ganges, Indus may not survive: climatologists]</ref><ref>[http://news.bbc.co.uk/2/hi/science/nature/3998967.stm Himalaya glaciers melt unnoticed]</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>[http://www.sciencedaily.com/releases/2008/03/080317154235.htm Glaciers Are Melting Faster Than Expected, UN Reports]</ref> ==== 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 effect plant [[physiology]] and cause massive amounts of [[mutation]]s, and indirectly through changed [[pollinator]] behavior, though such changes are difficult to quantify.<ref>[http://www.guardian.co.uk/uk_news/story/0,,1470944,00.html Ozone layer most fragile on record] ''Brown, Paul'' The Guardian April 2005</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 ground-level ozone, which would substantially lower yields.<ref>Dead link: http://news.independent.co.uk/world/environment/story.jsp?story=633349</ref> == Impact of agriculture on climate change == 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>[http://www.virtualcentre.org/en/library/key_pub/longshad/A0701E00.pdf Food and Agriculture Organization of the UN] retrieved 25 Jun 2007</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] ([[Intergovernmental Panel on Climate Change|IPCC)]]</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 Jun 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>[http://ipcc-wg1.ucar.edu/wg1/Report/AR4WG1_Pub_Ch02.pdf Intergovernmental Panel on Climate Change]</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://ipcc-wg1.ucar.edu/wg1/Report/AR4WG1_Pub_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% 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>[http://www.virtualcentre.org/en/library/key_pub/longshad/A0701E00.pdf Food and Agricultural Organization of the U.N.] retrieved 25 jun 2007</ref>) Livestock activities also contribute disproportionately to land-use effects, since crops such as [[corn]] and [[alfalfa]] are cultivated in order to feed the animals. Worldwide, livestock production occupies 70% of all land used for agriculture, or 30% of the land surface of the Earth.<ref>[http://www.virtualcentre.org/en/library/key_pub/longshad/A0701E00.pdf Food and Agricultural Organization of the U.N.] retrieved 27 jun 2007</ref> == See also == {{EnergyPortal}} * [[Land Allocation Decision Support System]] - a research tool that is used to test how climate change may affect agriculture (eg. yield and quality). * [[Desertification]] * [[Drought]] * [[Food security]] * [[Aridification]] * [[Water crisis]] * [[International Assessment of Agricultural Science and Technology for Development]] addressing the links between climate change & agriculture == References == * Fischer G., Shah M. and van Velthuizen H. (2002) [http://www.iiasa.ac.at/Research/LUC/JB-Report.pdf "Climate Change and Agricultural Vulnerability"]. International Institute for Applied Systems Analysis. Report prepared under UN Institutional Contract Agreement 1113 for World Summit on Sustainable Development. Laxenburg, Austria {{Reflist}} == External links == * [http://www.macaulay.ac.uk/LADSS/climate_change_wshop.html LADSS - Climate Change and Agriculture] - Are we asking the right questions? * John Vidal and Tim Radford, ''The Guardian'', [[June 30]], 2005, [http://www.guardian.co.uk/climatechange/story/0,12374,1517831,00.html One in six countries facing food shortage] * [http://www.greenfacts.org/en/agriculture-iaastd/index.htm#4 How is climate change threatening agriculture?] section of official popularized version of [[IAASTD]] synthesis report (2008) * Stories of how different farmers are being affected by climate change at [http://www.panda.org/climatewitness Climate Witness]. {{Global warming}} [[Category:Effects of global warming]] [[Category:Environmental soil science]] [[Category:Environmental issues with agriculture]] [[hu:A globális felmelegedés és a mezőgazdaság]]