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Arable land is turning to desert or to salt at an ever-faster rate, essening the hope that we can feed our booming population
By John Vidal
Within 40 years, there will be around 2 billion more people – another China plus India – on Earth. Food production will have to increase at least 40%, and most of that will have to be grown on the fertile soils that cover just 11% of the global land surface.
There is little new land that can be brought into production, and existing land is being lost and degraded. Annually, says the UN's food and agricultural organisation, 75bn tonnes of soil, the equivalent of nearly 10m hectares of arable land, is lost to erosion, waterlogging and salination; another 20m hectares is abandoned because its soil quality has been degraded.
The implications are terrifying. "The world is facing a serious threat of a major food shortage within the next 30 years. We are trying to grow more food on less land while facing increased costs for fertiliser, fuel and a short supply of water," says Professor Keith Goulding, head of sustainable oils at Rothamsted research station and president of the British society of soil science.
Lester Brown, president of the Worldwatch Institute in Washington, says it takes between 200 and 1,000 years to renew 2.5cm of soil. "The thin layer of topsoil that covers the planet's land surface is the foundation of civilisation. This soil, typically 6 inches [15cm] or so deep, was formed over long stretches of geological time as new soil formation exceeded the natural rate of erosion.
eut sometime within the last century, as human and livestock populations expanded, soil erosion began to exceed new soil formation over large areas." Soil erosion is not a high priority among governments and farmers because it usually occurs so slowly that its cumulative effects take decades to become apparent, says David Pimentel, professor of agricultural sciences at Cornell University. "The removal of 1 millimetre of soil is so small that it goes undetected. But over a 25-year period the loss would be 25mm, which would take about 500 years to replace by natural processes."
Soil erosion also leads to lower crop productivity because of loss of water, organic matter and soil nutrients. A 50% reduction in soil organic matter has been found to reduce corn yields by 25%. Countries are losing soil at different rates. The US, which just avoided turning the Great Plains into a dust bowl in the 1930s, is still losing soil 18 times more rapidly than it is forming it. China's desertification may be the worst in the world, Brown ays. "Wang Tao, a leading desert scholar, reports that from 1950 to 1975 an average of 600 square miles [1,550 sq km] turned to desert each year. By century's end, nearly 1,400 square miles [3,600 sq km] were going to desert annually.
Over the last half-century, some 24,000 villages in northern and western China have been entirely or partly abandoned as a result of being overrun by drifting sand." The problem is highly visible in the grasslands of Africa, the Middle East and central Asia. In 1950, Africa was home to 227 million people and 273 million livestock. By 2007, there were 65 million people and 824 million livestock. more>>
Courtesy: guardian.co.uk
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