The Guardian has an article on soil depletion - Earth has lost a third of arable land in past 40 years, scientists say.
The world has lost a third of its arable land due to erosion or pollution in the past 40 years, with potentially disastrous consequences as global demand for food soars, scientists have warned. New research has calculated that nearly 33% of the world's adequate or high-quality food-producing land has been lost at a rate that far outstrips the pace of natural processes to replace diminished soil.The University of Sheffield's Grantham Centre for Sustainable Futures, which undertook the study by analysing various pieces of research published over the past decade, said the loss was "catastrophic" and the trend close to being irretrievable without major changes to agricultural practices. The continual ploughing of fields, combined with heavy use of fertilizers, has degraded soils across the world, the research found, with erosion occurring at a pace of up to 100 times greater than the rate of soil formation. It takes around 500 years for just 2.5cm of topsoil to be created amid unimpeded ecological changes.
Link source: http://peakenergy.blogspot.com/2015/12/earth-has-lost-third-of-arable-land-in.html