People have lived in and around deserts since time immemorial where their activities and use of natural resources have been, and are, governed by the basic parameters defining all deserts. Rainfall, essential for growth and reproduction of plants and animals, for grazing and for agriculture, is a central factor. High temperatures and strong winds also influence people's use of deserts. Adaptations of people to these elements are different, mainly in degree but not in kind, from those of other animals and of plants. People have relatively few morphological and physiological adaptations with a predominance of behavioural, cultural and technological adaptations. People have used a variety of approaches to live in deserts and continue unusual innovations.

Although limited, the same physiological principles governing, for example, heat exchange in animals and plants pertain to human thermoregulation (Louw and Seely 1982). Humans, unlike many large mammals, do not pant in response to heat. Instead, humans sweat profusely and no other animal sweats as efficiently to support evaporative cooling. People can produce up to 4.2 litres of sweat per hour if well acclimated. Surprisingly, many people under hot conditions undergo considerable dehydration before drinking to replace lost body fluids. Heat stress, from increased body temperatures exacerbated by dehydration, may range from temporary loss of consciousness to stoppage of sweating, circulatory failure and death. Overall, key factors supporting humans in deserts are an adequate supply of water and shelter from the sun's direct rays.

Meagre physiological adaptations of people to deserts are more than adequately augmented by behavioural, cultural and technological adaptations. People are able to thrive in deserts simply by modifying their micro-environment. These modifications range from using natural shelters, for example caves or shade trees, to using appropriate clothing, to construction of dwellings and use of air conditioning. Behavioural, cultural and technological adaptations have evolved to ensure adequate food, water and shelter. The result of these adaptations has led to three major inter-related livelihoods: hunting and gathering, domestic livestock herding, and irrigated agriculture. While all these lifestyles are being practiced today, most have been extensively altered by modern technology.

Before describing traditional ways of resource use and management, brief consideration will be given to general aspects of people living in deserts. Protection from extreme heat and extreme cold is an important design consideration for desert clothing. Bedouin robes of light wool are considered to be an excellent compromise (Louw and Seely 1982). Evaporative water loss can be reduced by about one-third and heat gain by 55 per cent by wearing appropriate, loose-fitting clothing. Although white clothing will reflect solar radiation in the visible range, black or white clothes ensure the same body surface temperature. Nevertheless, two peoples living in deserts are known for wearing little clothing, the San people of southern Africa and the Aborigines of Australia (Biesele 1994, Bindon 1994).

Diet presents another aspect for consideration in hot deserts although basic requirements for highquality protein, vitamins, minerals and sufficient energy naturally apply (Louw and Seely 1982). Adequate water intake is of primary importance and, contrary to popular opinion, the normal amount of salt used for flavouring meals is sufficient. Very high protein intakes are undesirable. If present in sufficient quantities, the traditional diet of West Asia, based on low-protein cereal grains and protein-rich leguminous seeds and featuring tea and coffee while excluding alcohol, fulfils most theoretical criteria for an appropriate diet in deserts.

Heat and aridity also are important in terms of housing. The physical principles governing the design of permanent desert dwellings are well-known. Thick walls and small windows protect from the day's heat but do not allow for cool air circulation in the often still night hours. In many areas, this leads to people sleeping outdoors or on the roof. Strong winds are also a consideration. These winds go by many names in different parts of the globe: the Santa Ana in California, the föhn in the Swiss Alps and the zonda in Argentina. People, other animals and plants must deal with the increased evaporation and very low humidity of these winds. Moreover, solid edifices are not available to many desert dwellers, and other adaptations, for example low tents or transportable Mongolian ger, suffice while addressing the frequent occurrence of strong winds in addition to heat and aridity (for example, Flegg 1993).

This chapter will examine past and present livelihoods of people living in deserts, and their ever-changing relationships to available natural resources in these lands of scarce and unreliable rainfall, abundant sunshine, high temperatures and strong winds.