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  • Climate change and agriculture are interrelated processes, both of which

  • take place on a global scale. Climate change affects agriculture in a number

  • of ways, including through changes in average temperatures, rainfall, and

  • climate extremes; changes in pests and diseases; changes in atmospheric carbon

  • dioxide and ground-level ozone concentrations; changes in the

  • nutritional quality of some foods; and changes in sea level.

  • Climate change is already affecting agriculture, with effects unevenly

  • distributed across the world. Future climate change will likely negatively

  • affect crop production in low latitude countries, while effects in northern

  • latitudes may be positive or negative. Climate change will probably increase

  • the risk of food insecurity for some vulnerable groups, such as the poor.

  • Agriculture contributes to climate change by anthropogenic emissions of

  • greenhouse gases, and by the conversion of non-agricultural land into

  • agricultural land. Agriculture, forestry and land-use change contributed around

  • 20 to 25% to global annual emissions in 2010.

  • There are range of policies that can reduce the risk of negative climate

  • change impacts on agriculture, and to reduce GHG emissions from the

  • agriculture sector. Impact of climate change on agriculture

  • Despite technological advances, such as improved varieties, genetically modified

  • organisms, and irrigation systems, weather is still a key factor in

  • agricultural productivity, as well as soil properties and natural communities.

  • The effect of climate on agriculture is related to variabilities in local

  • climates rather than in global climate patterns. The Earth's average surface

  • temperature has increased by 1.5 °F since 1880. Consequently, agronomists

  • consider any assessment has to be individually consider each local area.

  • On the other hand, 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 income to exporting ones. The international

  • aspect of trade and security in terms of food implies the need to also consider

  • the effects of climate change on a global scale.

  • A study published in Science suggests 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%".

  • The Intergovernmental Panel on Climate Change 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 fishing industry will also be severely affected in some places.

  • Climate change induced by increasing greenhouse gases 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 and agricultural inputs

  • such as herbicides, insecticides and fertilizers

  • environmental effects, in particular in relation of frequency and intensity of

  • soil drainage, soil erosion, reduction of 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.

  • 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. In some cases, it seems that even minor

  • droughts have big impacts on food security, versus cases where even

  • relatively large weather-related problems were adapted to without much

  • hardship. Evan Fraser combines socio-economic models along with

  • climatic models to identifyvulnerability hotspotsOne such study

  • has identified US maize production as particularly 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. = Observed impacts =

  • So far, the effects of regional climate change on agriculture have been

  • relatively limited. Changes in crop phenology provide important evidence of

  • the response to recent regional climate change. Phenology is the study of

  • natural phenomena that recur periodically, and how these phenomena

  • relate to climate and seasonal changes. A significant advance in phenology has

  • been observed for agriculture and forestry in large parts of the Northern

  • Hemisphere. Droughts 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. Their impacts are aggravated because of

  • increased water demand, population growth, urban expansion, and

  • environmental protection efforts in many areas. Droughts result in crop failures

  • and the loss of pasture grazing land for livestock.

  • = Projections = As part of the IPCC's Fourth Assessment

  • Report, Schneider et al. projected the potential future effects of climate

  • change on agriculture. With low to medium confidence, they concluded that

  • for about a 1 to 3 °C global mean temperature increase 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. Over the same time period, with medium

  • confidence, global production potential was projected to:

  • increase up to around 3 °C, very likely decrease above about 3 °C.

  • Most of the studies on global agriculture assessed by Schneider et al.

  • 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 climate change. The US National Research Council

  • assessed the literature on the effects of climate change on crop yields. US NRC

  • stressed the uncertainties in their projections of changes in crop yields.

  • Their central estimates of changes in crop yields are shown above. Actual

  • changes in yields may be above or below these central estimates. US NRC 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. Projections suggested

  • that there could be large decreases in hunger globally by 2080, compared to the

  • 2006 level. Reductions in hunger were driven by projected 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.

  • Three scenarios without climate change projected 100-130 million undernourished

  • by the year 2080, while another scenario without climate change 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. The same set of greenhouse gas and

  • socio-economic scenarios were also used in projections that included the effects

  • of climate change. Including climate change, three scenarios projected

  • 100-380 million undernourished by the year 2080, while another scenario with

  • climate change 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. Projections also suggested regional

  • changes in the global distribution of hunger. 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.

  • Individual studies Cline 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 °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.

  • Lobell et al. 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 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 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" said C. Bellmann, ICTSD

  • Programmes Director. A 2009 ICTSD-IPC study by Jodie Keane suggests that