United Nations organizations are increasingly employing satellites and high-resolution imaging to combat desertification, pests and pollution. In one striking example, modern remote-sensing technology has come to the aid of Saudi Arabia's desert nomads, enabling them to locate fertile grazing areas without relinquishing their time-honored itinerant way of life.With the oil-rich Middle Eastern kingdom facing progressive urbanization and depletion of its natural resources, its estimated 400,000 nomads risked their centuries-old livelihood, as their camels, goats and sheep overgrazed rangeland. The traditional Bedouin vision ("Where next?") was blurred by sweeping changes imposed by modernization. The known oases were not as green as before and were steadily degrading, while nearby fertile grounds were undiscovered.Business as usualNow, a combination of satellites, the Advanced Very High Resolution Radiometer (AVHRR), the LANDSAT Thematic Mapper (TM), video cameras on aircraft, and University of Arizona researchers' expertise on drylands, allow the Bedouins to carry on with the occupation inherited from their forebears. The satellites relay information on where to move so there will be no further loss of vegetation. Global positioning satellite technology finds suitable grasslands to the exactness of 10 m.The Saudi Environmental Support of Nomad Project relies on two satellite-based sensors, the AVHRR, TM and airborne video data collection. The AVHRR provides daily coverage over large areas, and TM supplies six spectral bands at 30 m and one thermal infrared band at 120 m for refining. An aerial video system, under the auspices of the University of Arizona, provides further refinement. The Bedouins have their input, too: Over tea and dates, they tell interviewers of their needs.As a result, Bedouins have access to information on when the rains will come, how plant growth might progress and the carrying capacity of certain areas.Although the project affects only Saudi Bedouins, it has potential for some 300 million inhabitants of drylands, about half of which are facing desertification. The Rome-based International Fund for Agricultural Development, a UN agency participating in the project, says it hopes to extend the experiment to nomads in other countries as well.One other UN agency, the Food and Agriculture Organization, has already used remote sensing technology to provide similar aid to Africa, other sections of the Middle East and parts of Asia by monitoring food shortages and crop damage.