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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 (e.g., heat waves); 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.〔Hoffmann, U., Section B: Agriculture - a key driver and a major victim of global warming, in: Lead Article, in: Chapter 1, in 〕 Climate change is already affecting agriculture, with effects unevenly distributed across the world.〔Porter, J.R., ''et al.'', Executive summary, in: (Chapter 7: Food security and food production systems ) (archived (5 November 2014 )), in 〕 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.〔Paragraph 4, in: SUMMARY AND RECOMMENDATIONS, in: 〕 Agriculture contributes to climate change by (1) anthropogenic emissions of greenhouse gases (GHGs), and (2) by the conversion of non-agricultural land (e.g., forests) into agricultural land.〔Section 4.2: Agriculture’s current contribution to greenhouse gas emissions, in: 〕 Agriculture, forestry and land-use change contributed around 20 to 25% to global annual emissions in 2010.〔Blanco, G., ''et al.'', Section 5.3.5.4: Agriculture, Forestry, Other Land Use, in: (Chapter 5: Drivers, Trends and Mitigation ) (archived (30 December 2014) ), in: . Emissions aggregated using 100-year global warming potentials from the IPCC Second Assessment Report. 〕 There are range of policies that can reduce the risk of negative climate change impacts on agriculture,〔Porter, J.R., ''et al.'', Section 7.5: Adaptation and Managing Risks in Agriculture and Other Food System Activities, in (Chapter 7: Food security and food production systems ) (archived (5 November 2014 )), in 〕〔Oppenheimer, M., ''et al.'', Section 19.7. Assessment of Response Strategies to Manage Risks, in: (Chapter 19: Emergent risks and key vulnerabilities ) (archived (5 November 2014 )), in 〕 and to reduce GHG emissions from the agriculture sector.〔SUMMARY AND RECOMMENDATIONS, in: 〕〔Current climate change policies are described in and 〕〔Smith, P., ''et al.'', Executive summary, in: (Chapter 5: Drivers, Trends and Mitigation ) (archived (30 December 2014) ), in: 〕 == 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 (0.83 °C) 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 (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 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 (irrigation) and agricultural inputs such as herbicides, insecticides and fertilizers * ''environmental effects'', in particular in relation of frequency and intensity of soil drainage (leading to nitrogen leaching), 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 (such as what 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. Evan Fraser combines socio-economic models along with climatic models to identify “vulnerability hotspots”〔 One such study has identified US maize (corn) 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. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「climate change and agriculture」の詳細全文を読む スポンサード リンク
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