ABSTRACT
The dry lands of the world cover a large area of Earth's surface where moisture levels are limiting. In the tropics they extend from the savanna or seasonal forest zone to areas of extreme aridity in the desert cores. In polar regions and parts of continental interiors there are areas that qualify as dry in terms of their mean annual precipitation and the seasonality of water availability. Climatologists have devised indices based on the inputs of precipitation relative to evaporation outputs in order to quantify the degree of dryness. This chapter talks about dry lands as those areas of the world where there is a significant moisture deficit. The dry lands of the world cover a large area of Earth's surface where moisture levels are limiting. In the tropics they extend from the savanna or seasonal forest zone to areas of extreme aridity in the desert cores.
