Almost 75 percent of Central America s agricultural land has been seriously degraded, as has 20 percent of Africa s and 11 percent of Asia s, according to recent studies. This degradation has affected agricultural productivity, agricultural income, and economic growth, reports Scherr. The cumulative productivity loss for cropland from soil degradation over the past 50 years is estimated to be about 13 percent, and for pasture lands 4 percent. In South and Southeast Asia estimates for total annual economic loss from degradation range from under 1 to 7 percent of agricultural gross domestic product. Estimates for eight African countries show annual economic losses ranging from under 1 percent of agricultural GDP in Madagascar to 9 percent in Zimbabwe.
Poor people tend to suffer more than others from soil degradation.
The poor also often lack the capacity to invest in land improvements. Estimates of future land loss due to degradation vary widely, from 5 to 12 million hectares a year. Assuming that land loss continues at current rates, an additional 150 to 360 million hectares would go out of production by 2020. Although degradation appears likely to pose only a modest threat to global food supply or trade by 2020, some groups and regions will be particularly affected. Countries or subregions that depend on agriculture as the engine of economic growth will probably suffer.