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AGRICULTURE
source: www.fao.org/ag/magazine/
0103sp2.htm
www.gcrio.org/CONSEQUENCES/
summer95/agriculture.html
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Agriculture is responsible for an estimated 1/3 of global warming and climate change…- it is generally agreed that about 25% of the main greenhouse gas, carbon dioxide, is produced by agricultural sources, mainly deforestation and the burning of biomass;
- most of the methane in the atmosphere comes from domestic ruminants, forest fires, wetland rice cultivation and waste products, while conventional tillage and fertiliser use account for 70% of the nitrous oxides;
Climate change can impact agricultural sustainability in two interrelated ways:
- by diminishing the long-term ability of agro-ecosystems to provide food and fibre for the world's population: higher average temperatures of 2.5°C in 2080 could leave 50 million additional people at risk of hunger;
- by inducing shifts in agricultural regions that may encroach upon natural habitats, at the expense of floral and faunal diversity;
- agriculture of any kind is strongly influenced by the availability of water. Climate change will modify rainfall, evaporation, runoff, and soil moisture storage. The demand for water for irrigation is projected to rise in a warmer climate, bringing increased competition between agriculture - already the largest consumer of water resources in semiarid regions - and urban as well as industrial users;
- global projections in North America and northern Europe estimate agricultural yield increases for up to 2°C temperature rise, the cultivated area could be expanded northwards, and growing seasons extended. But beyond this level a decline is expected;
- in subtropical and tropical areas damage from increased heat stress is already projected even with a 1.7°C temperature increase. Agriculture could be threatened by climate change due to increased water stress;
- bad harvests could become more common due to an increase in the frequency of extreme weather events (droughts, floods, storms, hail), and pests and diseases;
- higher air temperatures will also be felt in the soil, where warmer conditions are likely to speed the natural decomposition of organic matter and to increase the rates of other soil processes that affect fertility. Additional application of fertilizer may be needed to counteract these processes. This can come at the cost of environmental risk, for additional use of chemicals may impact water and air quality;
- higher temperatures and increased soil salinity (salt content) could cause Bangladesh’s wheat production to drop by 61% and rice by 17%. Yields for the sorghum variety, which is the staple for 44% of Malians could decline by 26%.
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