For a rapid summary of current knowledge on deserts and drylands aimed at the general reader, the American Association for the Advancement of Science's (AAAS) four-page guide is hard to beat — even though it is a little out of date. The guide includes data on soil degradation around the world; a list of countries with large dryland areas; and a world map of dry lands. It acknowledges the uncertainty over the definition of desertification. It also points out that satellite images show the desert advancing and retreating several times since 1980 in regions such as the Sahel, depending in part on when it rains. The guide is published in the AAAS Atlas of Population and the Environment, which can be ordered or downloaded from this website.

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