Earth is running out of soil. At least thatÂ’s the conclusion of a new study supporting the long-held belief that current farming practices are causing soil to erode more quickly than new soil can be produced.
The best way to measure the effects of farming is a before-and-after comparison of soil erosion on the same kind of land, looking at both cultivated and wild-growing areas. David R. Montgomery of the University of Washington compiled the data and published his findings last August. On average, he found, plowed land erodes at slightly more than 1 millimeter per year, while new soil builds up at about 0.2 millimeter per year. Montgomery calculates that cultivated soil becomes exhausted, depending on original thickness, within 500 to several thousand years—a number correlating reasonably well with the life spans of civilizations around the world.
“Soil erosion is one of the least appreciated but most important environmental challenges we face,” Montgomery says. “It’s every bit as important as global warming. And part of the problem with both these things is the slow timescales over which problems accumulate.”