Geoscience Reference
In-Depth Information
4
Adaptations to life in deserts
The nomads will not burn the good pasture bushes ...evenintheir
enemies' country. ...Ihavesometimesunwittingly offended them,
until I knew the plants, plucking up and giving to the flames some
which grew in the soil nigh my hand.
Charles M. Doughty (1843-1926)
Passages from Arabia Deserta
(1931)
4.1 Introduction
Over very long intervals of time, the plants and animals living in deserts and their mar-
gins have become well-adapted through their morphology, physiology and behaviour
to using scarce water efficiently (Evenari et al.,
1971
; Stafford Smith and Morton,
1990
; Morton et al.,
2011
). Evenari et al. (
1971
) noted that the more extreme the desert
habitat, the more specific were the requirements for survival. The sparse human pop-
ulations in deserts have also evolved long-term behavioural adaptations to the harsh
extremes of desert climates, particularly through a nomadic lifestyle designed to make
optimum use of sporadic rains and ephemeral grazing. The sedentary communities
who live in deserts and depend on plant cultivation have learned to obtain and use
water with great ingenuity, as in the case of the underground water-conducting tun-
nels of the piedmont deserts of the Near East, central Asia, the Sahara and Mexico. In
those favoured desert localities where permanent springs exist, or where groundwater
can be tapped by wells and by deep-rooted, relatively salt-tolerant trees such as date
palms, larger human settlements become possible, but many oases are today facing
problems of falling water-tables and increasing salt accumulation in soils used for
growing crops.
4.2 Water in deserts
Without water life is not possible, and in deserts it is the availability of water that deter-
mines where plants, animals and humans can live (
Figure 4.1
). For plants, especially
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