Soil degradation is any type of problem that removes soil in an area or makes high-quality soil become poor. Careless agricultural practices, pollution and deforestation cause lots of soil degradation in the world. Several types of soil degradation exist and are a threat to natural forests and planted crops.

Erosion occurs when the topsoil that many plants need to grow gets blown or washed away. While some erosion is natural, the University of Michigan warns that humans often remove plants that cover soil and, therefore, speed up erosion. Since topsoil takes so long to build back up through natural processes, erosion damage is almost irreversible.

Acid rain causes soil degradation, according to the Environmental Protection Agency. The contaminated water gets into forest soils and retards tree and other plant growth. Acid rain comes from natural causes, like volcanoes, but a lot of it also comes from man-made industry emissions.

Too many salts accumulate in overly irrigated soils, causing soil degradation in the form of salinization. The University of Michigan explains that over-irrigation occurs when farmers grow crops in very dry land and have to irrigate it frequently. Salts then build up each time the soil dries out again, making it difficult for plants to grow in the soil.

Nutrient loss often occurs in conjunction with salinization. The United Nations explains that nutrient loss occurs through a variety of mechanisms, including leaching, erosion, runoff, crop uptake and denitrification. Michigan State University explains that crops uptake too many soil nutrients that farmers do not always replace. Deforestation and careless agricultural processes lead to soil degradation in the form of nutrient loss. After soil becomes nutrient-poor, crops and naturally occurring plants have a hard time growing in the area.