Investment (of a more formal kind than remittances) has a less certain trajectory. Inward investment was the strongest driver of change in deserts in the recent past. Most went to the extraction of oil, gas, iron, uranium, phosphates, nitrates, and copper, among other minerals. Even if no new reserves of oil are discovered, deserts contain a high percentage of global reserves, and this implies continued investment, if at a lower rate. Rising prices may maintain the income from older investments. Investment in gas is newer, and will probably increase. Iron ore contributes 40 per cent of Mauritania's export income; desert Western Australia contributed 16 per cent of the world's production of iron in 2003. Both will probably maintain their position, although iron prices fluctuate wildly. One-third of known recoverable global reserves of uranium are in Australia, but none of its desert reserves is currently mined. Namibia has about six per cent of known global recoverable reserves, and the Namibian mine is the only desert uranium mine currently in production. A global move to nuclear electricity generation would encourage the reopening of other reserves, as in Kazakhstan, Niger, and northern Chad (over which Chad and Libya went to war in 1987). North Africa (largely its deserts) holds about one-third of world reserves of phosphate.

Desert tourism, another source of investment, has grown quickly. Four million tourists visit Morocco and five million reach Tunisia each year. They contributed six per cent to Tunisian gross domestic product in 1999, and employed over 300 000 people. Desert destinations in both countries outperformed their coasts. There was a 161 per cent increase in tourism to Egypt in 2005. Dubai claims to be the world's fastest growing tourist destination; 100 000 British people have bought homes there, and it is aiming at 15 million tourist visits a year. Baja California is booming. More gambling is said to take place in deserts than in any other global environment. The upward trends may continue in some places, although some markets must be nearing saturation. If the past is a guide, the pattern of development will be patchy.

The steady growth in short trips, as to the U.S. deserts, is less likely to falter. They attract less investment, and probably generate less income, but involve more people. An estimated 800 000 people a year, and as many as 80 000 on a single weekend, already visit the Algodones Dunes in California, many to go dune buggying. The "Burning Man", a week-long cultural festival with international draw, is held annually on the playa of the Black Rock Desert in Nevada (Figure 5.3).

Large, cheap sites, which are superabundant in deserts, are a further source of investment (generally by the state). It is not only these qualities that attract this investment: it is also distance from prying eyes and air-borne attack, and freedom from planning objections. All this allows deserts to be used for purposes that would be difficult or even unimaginable in other regions; the first nuclear bomb was tested at La Jornada del Muerto in New Mexico in 1945; the U.S. plans to store nuclear waste in about 600 square kilometres of Yucca Mountain, Nevada. The French tested their nuclear bombs at Reggane in the Sahara and the British at Woomera in the Australian desert (a reserved area of about 127 000 km2), where Australian nuclear waste is now stored. Later came Lop Nur in the Chinese desert (about 100 000 km2), the Kharan Desert in western Pakistan, and Pokhran in desert India. Military training takes place in the Mojave Desert, the Omani Desert and the Negev Desert in Israel. Russia, China, Japan, and the United States have space-flight installations in the desert (Figure 5.4). Low-cost space in the California deserts is used to park huge numbers of unused aeroplanes. There are prisons in many deserts; Woomera is used to hold refugees, and the European Union is said to be planning a holding station for refugees in the North African desert. These intrusions import many people into deserts, generate considerable income, and help to upgrade infrastructure, but have large environmental footprints, particularly with respect to water. In an insecure and competitive world, this kind of investment will continue, even grow.