Planet Earth loses some 1 percent of its topsoil to erosion every year — and that’s an environmental threat on par with global warming, say experts. “Globally, it’s pretty clear we’re running out of dirt,” says geologist David Montgomery, who identifies agriculture as the main culprit for “soil mining.” In the U.S., cropland is estimated to be eroding at least 10 times faster than it’s replaced. Farmers with an interest in sustainability are trying to persuade others to adopt “no-till” and organic farming methods to address the problem, but “it’s hard to get people to pay much attention to this,” says soil expert John Reganold. “Frankly, most of us take soil for granted.”