What are the natural causes of land degradation ?

erosion from wind and rain. Changes in vegetation from foraging animals and storms can increase erosion as the roots of plants holds soils together. Removing the plants increases the amount of topsoil washed and blown away. Fire is another factor, but in some regions were fire is common the species have adapted to benefit from fire eg Australian sclerophyllous woodlands. Over long time periods geological events can lead to changes in local climate which can create deserts.