How does overgrazing result in desertification?

Overgrazing significantly contributes to desertification primarily because it increases the rate at which topsoil is eroded. When livestock graze too heavily on vegetation, they can remove protective plant cover, which normally helps to anchor the soil in place. Without sufficient vegetation, the soil becomes exposed to wind and water erosion. This erosion can lead to the loss of the nutrient-rich top layer of soil, which is crucial for plant growth.

As topsoil is eroded, the land becomes less fertile and more difficult for plants to re-establish, thus creating a cycle where the lack of vegetation permits further erosion. This process can lead to the transformation of once-productive land into arid or semi-arid conditions, characteristic of desertification. The increased erosion also diminishes the land's ability to retain moisture, exacerbating the aridity.

In contrast, while other options mention aspects related to vegetation and land use, they do not directly connect to the primary mechanism of how overgrazing leads to desertification like increased erosion does. The integration of this understanding emphasizes the importance of sustainable grazing practices to maintain healthy ecosystems and prevent desertification.