Natural climate variability can accelerate the process of desertification. Changes in the frequency and severity of drought contribute substantially to dryland degradation and desertification. Declining rainfall can also cause changes in vegetation, with, for example, perennial grasses giving way to annual growth, and shrubs giving way to grass cover. Long periods of high winds can remove fertile top-soils causing soil erosion. In tropical sub-humid regions, fields bare of vegetative cover may be eroded by excessive runoff at the start of the rainy season.
Desertification contributes to both regional and global climate change . . .
Reduced vegetation cover and soil quality can affect local climate by raising temperatures and reducing moisture levels. These effects may extend beyond the desertified area, resulting in regional changes in climate and atmospheric circulation, which in turn may accelerate the process of dryland degradation. Declining vegetation and soil quality can result in the release of carbon, while re-vegetation can lead to more carbon being absorbed from the air and stored in biomass. Nitrous oxide emissions may rise if more fertiliser is used to reclaim lands. These effects are small compared with the impact of global energy use , although at the national level they may be the most important source of greenhouse gas emissions for certain states. and global climate change may contribute to desertification.