PEAK SOIL

I've had a compost pile since college.

www.sierraclub.org/sierra/201111/grapple5.aspx

"Erosion" is a dirty word. The world is losing soil 10 to 40 times faster than nature can replenish it, leaving us literally dirt-poor. Ethiopia loses 2 billion tons of topsoil each year, and China 4.5 billion. Iowa lost nearly half its dirt in the past century.

Over the past four decades, a third of the earth's prime agricultural land has become too eroded to farm on. And the world's growing population needs it more than ever.

"If we still had the fertile soils we had in 1900, we'd have a far easier time feeding the world 50 years from now," says David Montgomery, author of Dirt: The Erosion of Civilizations.

Soil has been going downhill ever since our Neolithic ancestors began tilling the land 10,000 years ago, but dirt depletion is now accelerating, thanks to chemical fertilizers, mechanized cultivators, a lack of cover crops, overgrazing, and population pressures that push marginal land into cultivation. The torrential downpours that come with climate disruption exacerbate the problem, washing away topsoil and releasing soil-sequestered carbon dioxide into the atmosphere.

So, take good care of your own little patch of earth. It took 500 years just to form the top inch of it, and it may have to produce enough food to feed you—and a few billion others.