Friday, May 23, 2008

WE'RE RUNNING OUT OF DIRT. . AND WE NEED IT

TOM PAULSON, SEATTLE POST INTELLIGENCER The planet is getting skinned. While many worry about the potential consequences of atmospheric warming, a few experts are trying to call attention to another global crisis quietly taking place under our feet.

Call it the thin brown line. Dirt. On average, the planet is covered with little more than 3 feet of topsoil -- the shallow skin of nutrient-rich matter that sustains most of our food and appears to play a critical role in supporting life on Earth.

"We're losing more and more of it every day," said David Montgomery, a geologist at the University of Washington. "The estimate is that we are now losing about 1 percent of our topsoil every year to erosion, most of this caused by agriculture."

"It's just crazy," fumed John Aeschliman, a fifth-generation farmer who grows wheat and other grains on the Palouse near the tiny town of Almota, just west of Pullman. . .

The National Academy of Sciences has determined that cropland in the U.S. is being eroded at least 10 times faster than the time it takes for lost soil to be replaced. . .

Healthy topsoil is a biological matrix, a housing complex for an incredibly diverse community of organisms -- billions of beneficial microbes per handful, nitrogen-fixing fungi, nutrients and earthworms whose digestive tracts transform the fine grains of sterile rock and plant detritus into the fertile excrement that gave rise to the word itself ("drit," in Old Norse).

As such, true living topsoil cannot be made overnight, Montgomery emphasized. Topsoil grows back at a rate of an inch or two over hundreds of years. Very slowly.

"Globally, it's pretty clear we're running out of dirt," Montgomery said.