Breeding and agriculture have eroded almost all of the Alps soil

Rapid erosion due to human activity, such as grazing, livestock and agriculture, has stripped the Alps of almost all the soil formed since the retreat of the glaciers. This soil has developed during the millennia while plants, microbes and weather conditions have transformed the hard rock into a carbon -rich foundation of this mountain ecosystem.

“We destroyed the soils at a rate of four to 10 times faster than they grew up,” said William Rapuc at the French National Center for Scientific Research.

He and his colleagues have studied the isotopes of lithium in the sediments of Lake Bourget in the French Alps to rebuild the ground erosion models of the surrounding region over the past 10,000 years. Because some lithium isotopes are enriched in clay and other minerals are formed from the parental rock, they can tell you if the soils are developing or eroding, explains Rapuc.

They then compared these soil erosion patterns of the sediment of the lake with other recordings of the evolution of the climate and human activity in the region. During the first millennia after the glaciers fell, changes in the climate could explain the soil loss patterns. Then, about 3,800 years ago, something changed. “What is not explained by the climate … must be explained by the impact of humanity,” explains Rapuc.

The researchers identified three overvoltages of the loss of soil, each of which they think correspond to a different type of human activity in the region. 3800 to 3000 years ago, the push came from the grazing cattle to higher altitudes. Agriculture in Lower Altitudes has led the next increase, which occurred between 2,800 and 1600 years, and more intensive agriculture using plows and other tools led the final push 1600 years ago until today. The loss of soil in the Alps accelerates the erosion of wind and water, and means that the region has less capacity to support vegetation and crops.

The researchers say that this change 3,800 years ago marks the beginning of an “soil anthropocene” in the region, in which humans are the dominant influence on the soil. But this past influence of the soils “is nothing compared to what we can do now,” explains Rapuc.

For example, in the United States, where the soil anthropocene started only a few centuries ago, the loss of soil occurs at a rate up to 1000 times faster than before the last glacial period, explains Daniel Rath at the Natural Resources Defense Council, an environment defense group. “We are fundamentally changing how soils are really trained and developed due to our agricultural activities.”