People in the dryland environments

As with other life forms, the human inhabitants of dryland regions need to cope with excessive thermal stress and maintain sufficient water supply. A critical need is for the temperature of the body to remain within tolerable limits, but comfort is also a factor. Water plays a major role in thermal regulation, and it is also required for cellular functioning. The ways in which humans avoid thermal stress are comparable to those of animals, especially in terms of physiological response to stress. Unlike plants and animals, humans can actively manipulate the thermal response of their body, through choice of clothing for example, and can actively manipulate their environment, through construction of their dwellings. They can also conceive of strategies to minimize water demand and optimize its availability. Humans also require energy. Modern technology provides additional options for coping with the dryland environment, but this chapter will focus primarily on traditional adaptations to dryland environments. The involuntary physiological responses of the body, as well as clothing, architecture, livelihood/lifestyle and ways to meet energy and water demands are examined.

Heat balance and comfort of the human body

The surface heat balance concept presented in Chapter 6 can readily be applied to the human body (Fig. 23.1). The body receives heat through direct and diffuse solar radiation and solar radiation reflected from various surfaces in the environment. It also absorbs longwave radiation given off by the surface and atmosphere. The body cools via longwave radiation and sensible heat transfer (conduction and convection) from the skin and via latent heat transfer (evaporative cooling via sweating). Additional cooling mechanisms for the human body include warming of inhaled air and evaporating moisture into inhaled air. Heat is generated via metabolic activity, but much of this is lost to mechanical work (i.e., movement/exercise) (Young 1979).