Climate change
The consequences of global climate change on agriculture and ecosystems are highly uncertain. Based on simulation models, the most likely impacts are netfavourable effects for the cooler margins of the temperate zone, and adverse consequences for the sub-tropical semi-arid zone (see box). Regional changes in climate have already affected diverse physical and biological systems in many parts of the world. Mid- to high-latitude growing seasons have lengthened. Poleward and altitudinal shifts of plant and animal ranges have been observed (IPCC 2001). Natural systems at risk of climate change include glaciers, atolls, polar and alpine ecosystems, prairie wetlands and remnant native grasslands. Human systems that are vulnerable include agriculture, particularly food security, and forestry.
| Population controversy |
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'Many people identify growing population pressures of the poor and the resultant overgrazing, deforestation and unsustainable agricultural practices as major causes of desertification. This theory, however, is based on the assumption that only the poor and their growing populations cause environmental degradation. It misses the impact of a chain of international trade and economic practices which result in low prices for agricultural and livestock commodities for the South; and political compulsions such as debt, which force a country to promote adverse land use practices in order to earn foreign exchange. In its simplistic reaction, the West chooses to provide food, first through aid and then by promoting increased agricultural production. The problem still persists, showing that the solution is far more complex.' |
| Source: CSE 1999 |
From the 1990s, the climate change issue directed attention to the role of land as a terrestrial store of carbon. Land degradation almost always involves a loss of soil organic matter. If this trend can be checked or reversed, a considerable potential exists for carbon sequestration through building up the levels of carbon stored in soils and the vegetation cover (IFAD/FAO 1999).
| Climate change impacts on land and biodiversity by region | |
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| Region | Adaptive capacity, vulnerability and key concerns |
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| Africa |
Grain yields are projected to decrease for many scenarios, diminishing food security, particularly in small food-importing countries. Desertification would be exacerbated by reductions in average annual rainfall, run-off and soil moisture, especially in Southern, Northern and Western Africa. Significant extinctions of plant and animal species are projected and would affect rural livelihoods, tourism and genetic resources. |
| Asia and the Pacific |
Decreases in agricultural productivity and aquaculture due to thermal and water stress, sea-level rise, floods and droughts, and tropical cyclones would diminish food security in many countries of arid, tropical and temperate Asia; agriculture would expand and productivity would increase in northern areas. Climate change would exacerbate threats to biodiversity due to land-use and land-cover change and population pressure in Asia. In Australia and New Zealand, the net impact on some temperate crops of climate and CO2 changes may initially be beneficial but this balance is expected to become negative for some areas and crops with further climate change. Some species with restricted climatic niches and which are unable to migrate due to fragmentation of the landscape, soil differences or topography could become endangered or extinct. |
| Europe | There will be some positive effects on agriculture in northern Europe; productivity will decrease in southern and eastern Europe. |
| Latin America |
Yields of important crops are projected to decrease in many locations in Latin America, even when the effects of CO2 are taken into account; subsistence farming in some regions of Latin America could be threatened. The rate of biodiversity loss would increase. |
| North America | Yields of important crops are projected to decrease in many locations in Latin America, even when the effects of CO2 are taken into account; subsistence farming in some regions of Latin America could be threatened. The rate of biodiversity loss would increase. |
| Polar | Natural systems in the polar regions are highly vulnerable to climate change and current ecosystems have low adaptive capacity; technologically developed communities are likely to adapt readily to climate change but some indigenous communities, in which traditional lifestyles are followed, have little capacity and few options for adaptation. |
| Small Island States |
The projected sea-level rise of 5 mm/year for 100 years would cause enhanced coastal erosion, loss of land and property, dislocation of people. Limited arable land and soil salinization makes agriculture of small island states, both for domestic food production and cash crop exports highly vulnerable to climate change. |
| Source: IPCC 2001 | |
