What is soil erosion primarily caused by?

Soil erosion is primarily caused by water, wind, or human activity, which includes various processes that remove the top layer of soil, leading to degradation and loss of fertile land. Water can cause erosion through rainfall, surface runoff, and rivers, which wash away topsoil. Wind erosion is particularly prevalent in arid and semi-arid regions where loose, dry soil can be lifted and carried away, significantly reducing soil quality. Human activities, such as deforestation, overgrazing, and improper farming practices, can further exacerbate these natural forces by disturbing the soil structure, reducing vegetation cover, and accelerating the erosion process.

The other options fail to account for the factors that lead to soil erosion effectively. Increased biodiversity typically contributes to soil health and stability, as a diverse ecosystem can improve soil structure and reduce erosion. Crop rotation and organic farming practices are management techniques aimed at enhancing soil quality and fertility, and they often serve to protect against erosion by promoting soil structure and minimizing disturbances. Thus, while these practices can mitigate erosion, they do not directly cause it, making them less relevant to the question.