Soil erosion threatens to leave earth hungry

John Vidal in the Guardian (UK): 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 soils 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. But 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."…

Buried machinery in 1936 in Dallas, South Dakota, during the Dust Bowl