The main cause of land degradation is from human activities, from badly managing the land and the land cover. Activities which can be particularly harmful include:.
Clearing of vegetation, especially on steep slopes. This leaves the soil open to erosion by water.
Cultivating the land for too long without putting anything back. Crops take the goodness (the nutrients) out of the soil to help them grow strong; if these nutrients are not replaced, the soil slowly loses its ability to support crops. Nutrients can be restored by fallowing, by adding manure or fertilisers, by growing crops to plough back into the soil (green manuring), and by digging in crop residues instead of burning them.
Ploughing up and down slopes causes rainwater to flow down the slope along the furrows, and leads to erosion.
Overgrazing, where the ability of the grass to regrow the next year is damaged. This often causes bare patches, which then can be eroded by the wind. This is a particular danger in contained systems, where the animals are not free to move.
Changing the water situation (the hydrologic regime) so that the vegetation, land use, and even the soils change.
Is it permanent?.
Land degradation may be permanent or reversible. Where it is permanent, there is no way of bringing the land back into its former productive use. Often land degradation can be reversed, or at least the land can be brought back to a productive level, although it is never as good as it was originally. Actions can be taken to rebuild the soil - such as green manuring (growing crops to plough back into the soil while they are still green), long rest periods, etc. This is the traditional system in Africa; shifting cultivation led to local land degradation which was then reversed by long periods of fallow. However, today, with greater demand to use the land, leaving the land to rest is not always an option so we rely on fertilisers and other inputs to keep the land productive.
