In the past, expansion and intensification of agriculture have often damaged the very resources essential to farming - such as soil, water and the genetic diversity of crops - as well as the wider environment.
Soil erosion and other forms of land degradation rob the world of 5 million to 7 million ha of farming land every year. Clearing forests or growing crops on steep slopes or on large fields without protection against the wind can lead to erosion.
Waterlogging and salinization caused by poor drainage have sapped the productivity of nearly half the world's irrigated lands. Some 30 million ha have been severely damaged and an additional 1.5 million ha are lost each year.
Excess use of mineral fertilizers and pesticides can pollute surface and groundwater sources. Nitrates from fertilizers and feedlot wastes have contaminated groundwater in many countries and have been identified as a health risk, especially for infants. At the same time, in some countries the use of too little fertilizer depletes soil nutrients and contributes to soil degradation.
Loss of genetic diversity has accelerated with the spread of intensive agriculture and high-yielding crop varieties to large parts of the developing world, replacing the traditional diversity of crops with monocultures.
Deforestation accelerated during the 1980s, with more than 15 million ha of tropical forests lost each year, mainly to provide land for agriculture.
Agriculture also contributes significantly to release of greenhouse gases that have been linked to global warming. Some 30 percent of carbon dioxide emissions result from deforestation and other land use practices such as rangeland burning and agriculture may account for as much as 90 percent of nitrous oxide emissions.
The challenge for the future will be to simultaneously intensify production and minimize harm to the resources and the wider environment upon which present and future generations depend.
source: http://www.fao.org/wfs/fs/e/agricult/AgEnv-e.htm 31jan01
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