How does erosion affect plants?

How plants shape soil erosion

Plant roots usually provide solid soil. And the thicker the vegetation, the lower the soil erosion. Rain, on the other hand, loosens the soil and promotes erosion. However, this popular opinion is by no means universally valid, as a study now shows. In a large-scale study, geoscientists from the University of Tübingen focused for the first time on the complex relationship between vegetation, precipitation and soil erosion. Todd Ehlers' team selected the 3,500 kilometer long western edge of the Andes in Peru and Chile as the study area. This region comprises six climatic zones and ranges from very arid to temperate.

Mountain formation in the Andes investigated

The researchers wanted to know what influence the interplay between plant growth and climate has on mountain formation in the Andes. “One could assume that the denser the vegetation, the less erosion there is. This simple connection is true for some Andean regions, ”concludes Ehlers. If the precipitation is added, however, the picture changes. Because rain promotes plant growth, but also erosion.

Plant roots can loosen solid rock

Like the researchers in the specialist journal Science now report, the influence of vegetation on soil erosion is very different in the climatic zones. According to this, plants can also increase erosion by converting solid rock into soil with their roots, which can then be removed. For example, the sparse vegetation in the dry Atacama Desert provided solid ground. In contrast, the researchers found that in temperate, wetter areas with a denser vegetation cover, the rate of erosion was even higher. The team was able to observe that there is a dense vegetation cover in the climatically moderate Andean regions only because a lot of rain falls there. However, despite the numerous plants, this generally increases soil erosion. In other regions, however, the erosion was reduced by plants, so that slopes were stabilized and became steeper.

Measurements of the nuclides complete the picture

To determine the erosion rate, the researchers used so-called cosmogenic nuclides, which are created on the earth's surface by radiation from the cosmos. However, these only accumulate in exposed soil. On the basis of such measurements, the researchers were able to calculate how quickly mountains in the Andes are being eroded. “Our investigation along this wide climate gradient in the Andes helps to combine the observations of many other studies,” says Ehlers. But only an overview would show how plants and climate interact with the topography. "Our study is an example of a new scientific frontier that lies at the interface between the geosciences and the life sciences," says the researcher. "We are learning more and more about how strongly the solid and living parts of the earth interact, and we can observe the effects of these interactions over long time scales of thousands of years. "