Rather than desertification meaning the literal expansion of deserts, it is a catch-all term for land degradation in water-scarce parts of the world. This degradation includes the temporary or permanent decline in quality of soil, vegetation, water resources or wildlife, for example. It also includes the deterioration of the economic productivity of the land – such as the ability to farm the land for commercial or subsistence purposes. Arid, semi-arid and dry sub-humid areas are known collectively as “drylands”.