Deforestation and Soil Loss

Deforestation and Soil Loss

The forest and it’s natural resources has recently received growing attention from environmentalists because of the depletion and destruction of the forest cover. Forests play a vital role in the ecosystem. They provide a shield to help keep temperatures down, to maintain moisture, and assist in the growing activity of the soil. Tree cover also helps in reducing evaporation and soil runoff. The soil cover helps to absorb and infiltrate the larger amounts of rainfall. Forests also provide as a basin for green house gases. The process of deforestation is destroying this valuable land resource. Many environmentalists have attributed destruction of the forest resource to population growth, economic development, wanting to clear land to cultivate cash crops for export, and also unclear government policy.

Deforestation is having extremely severe effects in areas that contain some of the remaining natural sub-humid Mediterranean forests. These forest areas are rapidly being depleted. Over grazing, cultivating of forest margins, and firewood gathering leads to considerable loss of forests and croplands.

With deforestation comes soil loss. The removal of trees and shrubs exposes the soil which leads to erosion. Erosion leads to the removal of the thin upper soil layers. This, in turn reduces organic matter content and vegetation growth. Soils that lose organic matter can no longer retain moisture between rainy seasons; when precipitation increases, the soil remains unproductive.

The most significant type of soil loss is through landslides. Landslides induce soil loss by mass movement, and occur in natural forests and grasslands. Increased frequency of landslides often occurs in areas recently deforested. They remove soil under indigenous forests and that soil is then replaced by new vegetation cover.

Another form of soil loss is from intense rain after deforestation. When deforestation takes place the soil is left with nothing to protect it. Also, when trees exist the rain does not often reach the soil at full impact, so the soil is very loose and can be easily washed away. High intensity storms remove the eroded regolith. As less regolith is available to be removed, the frequency of landslides decreases. It is highly unlikely that the soil will accumulate to the same depth, as it was when forest cover was present.

Allowing forests to grow in their natural state will prevent soil degradation, and will decrease the chance of landslides. We assume in natural forests that there is a balance between soil erosion and soil reformation.