Geoscience Reference
In-Depth Information
precipitation in order to grow, reproduce and store food in the form of starch for
harsher times. Animals likewise have evolved ways to use water efficiently, to build
up fat when conditions are good and to insulate themselves from extremes of temper-
ature with woolly coats, night time foraging or hunting and occupying cool burrows
by day. Humans have also devised ingenious ways to divert and store water from
below the surface. Desert dwellers have adopted four primary life styles, of which the
hunter-gatherer tradition is the most ancient and a carryover from prehistoric times.
Nomadic pastoralism originated during the Neolithic some 10,000 years ago, when
certain suitable herd animals were first domesticated. Neolithic farmers also prac-
tised simple forms of rain-fed cultivation, many of which are still widely used in the
semi-arid world today. Finally, in selected localities where perennial supplies of water
could be obtained, either from shallow groundwater or from permanent rivers like the
Nile, which flowed through the desert, irrigated agriculture was initiated some 5,000
years ago. A major problem facing many desert populations today is the excessive
use of groundwater at a rate faster than the current rate of replenishment, in effect
depleting these non-renewable fossil groundwater supplies. Pollution of the aquifers
from indiscriminate use of pesticides and fertilisers has exacerbated these problems.
However, many societies have adapted well to arid conditions in a manner that shows
that sustainable use of our arid lands is indeed possible. We return to this topic in the
final chapter (
Chapter 26
) of this topic.
