Population in deserts will change, but unevenly. Few people, mostly pastoralist nomads, live in the great spaces of the desert. Even if the high birth rates often described for some nomad groups were true, the additional numbers would be few. Much larger mining and drilling communities will also have little overall impact. They consist, and will continue to consist, disproportionately of young, short-stay men, whose numbers fluctuate with the price of minerals. In Leonora, an old mining town in Western Australia, over 60 per cent of the population is still male, a century after its foundation.

Rural groups living along the great rivers will have more impact. Scattered, long-established, smaller oases have the same demographic dynamics, but smaller numbers. The World Economic and Social Survey (UNDESA 2005) predicts a steady decline in fertility in these populations, but also overall natural growth for some years. In Egypt, for example, the number of 25-28 year-old men will grow from 3.6 million in 2005 to peak at 3.8 million in 2025, before dwindling. This will put increasing demands on resources, particularly water, and may lead to dissatisfaction with unemployment. But the production of so much potential labour has a more positive implication, because labour is desperately needed in the industrialized world: in Italy, the number of 2-28 year-old males has already peaked and will have halved by 2025; an extreme, but characteristic case. Labour-seeking industries may be attracted to these growing desert populations, but because the greatest demand for labour is in the service sector, more of the surplus will gravitate to the industrialized world, and this will boost a counter-flow of remittances. In Pakistan, remittances peaked in 1982-83, when they contributed 75 per cent to the overall balance of trade (Amjad 1986). In 2002, remittances to the developing world were already US$67 billion, against government and bank lending of US$14 billion (Islam 2003).

Two further groups will have much greater impact. Both have grown and will grow quickly, but by immigration, not by natural increase. The smaller of these two groups is rapidly growing, and uses resources at a high per-capita rate. This group consists of retired migrants to the desert, and inhabits principally parts of the U.S. southwest (Figure 5.1). Growing numbers now also live in the United Arab Emirates (Figure 5.2). Very many more people live in cities like Lima, Cairo, Baghdad, Riyadh, Karachi, Kashgar (Kashi), Urumqi and Yarkand, all with populations of over five million. All have grown and will continue to grow quickly, and all attract many more men than women. Some depend on the production of oases (Cairo and the western Chinese cities); others are supplied from further afield. All consume large quantities of water, although all also pass on large quantities of reusable water.