Deforestation and intensive agriculture can accelerate erosion so dramatically that in just a few decades as much soil can be lost as would naturally occur over thousands of Deforestation and intensive agriculture can accelerate erosion so dramatically that in just a few decades as much soil can be lost as would naturally occur over thousands of years, according to a new study published online in the February issue of the journal Geology. Scientists from the University of Vermont quantified the rate of erosion for ten large river basins in Southeast U.S.A., collecting sediment samples from the rivers and measuring their beryllium-10 content. The amount of beryllium can reveal rates of erosion in the surrounding landscape. Along the southern Piedmont from Virginia to Alabama, clay soils built up for many millennia. The study suggests that rates of hillslope erosion before European settlement were about an inch (2.5 centimetres) every 2,500 years. Then, in just a few decades of intensive deforestation and cotton and tobacco production, as much soil eroded as would have happened in a pre-human landscape over thousands of years, the scientists found. “Soils fall apart when we remove vegetation and then the land erodes quickly”, says Paul Bierman, a geologist at the University of Vermont and co-author of the study. During the period of peak land disturbance in the late 1800s and early 1900s, rates spiked to an inch every 25 years. “Our study shows exactly how huge an effect European colonisation and agriculture had on the landscape of North America,” says Dylan Rood, a member of the research team. “Humans scraped off the soil more than 100 times faster than other natural processes!” Since the Earth does not create that precious soil for crops fast enough to replenish what the humans removed, it is a trend that is unsustainable if continued, the authors warn. According to the researchers, the results of their study could be used to develop smart environmental policies and regulations that will protect threatened soil and water resources for generations to come. (ab)