Land degradation is damage to land that makes it less economically useful and less biologically diverse. Degradation of the natural environment is a worldwide problem, and some examples are quite ancient. This term is used specifically to refer to damages caused by human activities rather than natural ones, and human activities can indirectly contribute to environmental changes that may accelerate the speed of land degradation.
In land degradation, land that was once rich in nutrients and able to support diverse organisms becomes compromised. Some types of degradation include salinification and acidification of soils, topsoil loss, soil compaction, and pollution of land that makes it unusable. The more degraded the soil becomes, the less it can support. This can cause degradation to speed up, as plants and animals that would normally help restore the soil are unable to survive.
Agricultural practices are a common culprit in land degradation. Overworking the soil can damage it, sometimes permanently. A modern example of degradation can be seen in the infamous Dust Bowl of the 1930s, when large-scale topsoil loss occurred as a combination of intensive agricultural practices and drought conditions. Degradation can also be the result of overutilization of timber resources that destabilizes the ecosystem; as trees are cut down, the organisms they support are no longer able to survive.
Industrial pollution from activities such as mining and manufacturing can also contribute to or cause degradation. In this case, the soil is damaged by release of chemicals into the soil and water. These chemicals may kill off plants and animals, reducing biological diversity. They can also lead to soil compaction and other declines in soil quality. Poor soil and water quality can be seen at sites used historically for manufacturing, illustrating that it can take decades or centuries for the land to fully recover.
The process of restoring land that has become degraded is known as remediation. In remediation, people identify the causes of the land degradation and explore methods for reversing it. Usually remediation takes time, as scientists want to encourage the land and ecosystem to rebuild and become stable again rather than enacting a quick fix. In some cases, land is too badly degraded for remediation to be effective, forcing human populations that relied on the land to relocate in order to access new resources. This in turn can contribute to population pressures in other fragile environments, ultimately repeating the land degradation all over again.