ABSTRACT
Drylands cover 40 per cent of the land area of the Earth: their total area is about 60 million km2, of which about ten million km2 are hyper-arid deserts (Fig. 1.1). Drylands support over one fifth of the world’s population, and arid and semi-arid lands together over a third. Living conditions vary from the most affluent and profligate to the desperately poor-in some cases in close proximity. The political stability and ecological, economic and social sustainability of dryland settlement are among the most daunting challenges confronting the global community in the twenty-first century: water seems likely to be a primary flashpoint for disputes between neighbouring states, with dryland irrigation systems under strain from fast-growing populations;
and with environmental refugees from global warming predicted to be in the order of 150 million by the year 2050 under the business-as-usual scenario (Houghton, 1997), the catastrophic consequences will be particularly acute for dryland populations.
