The lowdown on topsoil: It’s disappearing
Disappearing dirt rivals global warming as an environmental threat
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.”…
Montgomery has written a popular book, “Dirt,” to call public attention to what he believes is a neglected environmental catastrophe. A geomorphologist who studies how landscapes form, Montgomery describes modern agricultural practices as “soil mining” to emphasize that we are rapidly outstripping the Earth’s natural rate of restoring topsoil.
“Globally, it’s clear we are eroding soils at a rate much faster than they can form,” said John Reganold, a soils scientist at Washington State University. “It’s hard to get people to pay much attention to this because, frankly, most of us take soil for granted.”
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.
The United Nations has warned of worldwide soil degradation — especially in sub-Saharan Africa, where soil loss has contributed to the rapidly increasing number of malnourished people…
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… [more]