Humans said have huge impact on erosion

The main cause of man-made erosion is agriculture, followed by construction and mining.

Where humans once used sticks and stones, they have since developed technology that dramatically accelerated the speed of erosion, Wilkinson said.

Wilkinson's estimates from the Phanerozoic eon — about 542 million years ago — indicated that natural erosion took place at a rate of about five gigatons of sediment per year.

Between the Phanerozoic eon and the Pliocene epoch — about 5.3 million to 1.8 million years ago — erosion increased to about 16 gigatons per year as continental glaciers plowed across the Earth's surface and then retreated. Current estimates of natural erosion stand near 21 gigatons per year.

There's also a major difference in where the erosion is occurring, Wilkinson said.

Natural erosion occurs at the planet's highest elevations. Wilkinson said about 83 percent of the global river sediment comes from the highest 10 percent of the Earth's surface.

Human-induced erosion, by contrast, occurs in the lower elevations. Eighty-three percent of this erosion occurs at the lower 65 percent of land surfaces.

Wilkinson said his findings are significant not only to the field of geology, but to concerns about sustainable living as well.

The data indicate that given the continuing population growth on the planet, the soil loss caused by erosion will present a serious challenge to meeting the food needs of a growing population.

Global cropland has increased by 11 percent since 1961, while the global population has approximately doubled, Wilkinson said. The net effect of both changes is a 44 percent decrease in per capita cropland.

"Erosion by itself is not necessarily a crisis, but when you have more and more people, and less land on which to grow food, then you have a real problem," he said.

Reports in recent years show erosion rates decreasing in the United States, which has invested billions in improved farmland conservation practices, said Mark Nearing, a soil scientist and erosion expert for the U.S. Department of Agriculture. However, those figures do not take into account recent climate changes that are again accelerating erosion, he said.

Although he had not read Wilkinson's study, Nearing concurred that human-induced erosion is "an order of magnitude" greater than natural rates.

"There is no doubt that our (U.S.) erosion rates are unsustainable in the long run," said Nearing, adding that the rates in Latin America, Southeast Asia and Africa are much worse.

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