are defined as lands where annual precipitation is less than two
thirds of potential evaporation, from dry sub-humid areas (ratio
ranges 0.50–0.65), through semiarid, arid, and hyper-arid (ratio
<0.05) areas, but excluding polar areas; drylands include cultivated
lands, scrublands, shrublands, grasslands, semi-deserts, and true
deserts (Millennium Ecosystem Assessment, 2003:55) . Please refer to
Highlights for details.