People Erode Soil 100 Times Faster Than Nature

Cutting down or burning native forests and starting intensive agriculture -- that is, industrial-scale farming, designed to produce high yields of crops and/or animals -- can accelerate erosion dramatically, reports a newly-published study from researchers at the University of Vermont.

It causes so much damage, in fact, that in a few decades as much soil is lost as would naturally occur over thousands of years.

The researchers, who studied 10 large river basins in the southeastern United States, found that the damage started to occur hundreds of years ago, when large numbers of settlers arrived from Europe, and accelerated as agriculture developed. Before the 1700s, hillsides along the rivers eroded at a rate of about an inch each 2,500 years. But by the time erosion peaked in the late 1800s and early 1900s thanks to logging and tobacco and cotton cultivation, the hills were losing an inch every 25 years.

“Our study shows exactly how huge an effect European colonization and agriculture had on the landscape of North America,” says one of the researchers, Dylan Rood, “humans scraped off the soil more than 100 times faster than other natural processes.”

The study was published in the journal Geology.

The scientists came up with their findings by collecting sediment samples and then using an accelerator mass spectrometer at the Lawrence Livermore National Laboratory to help them measure the quantity of a rare isotope, beryllium-10, in quartz in the sediment. The isotope, formed by cosmic rays, builds up in the top of soil. As the erosion rate increases, the soil accumulates less beryllium-10.

Read more at Discovery News