Desertification is brought about by our planet's progressively changing climate - the world is becoming warmer and drier, and this means there is less water to support plants and animals. However, the natural rate of desertification has been greatly increased as a result of exploitation by the desert's human inhabitants. The causes of this increase are similar in many ways to those that bring about deforestation, and once again, the chief culprit is agriculture.
People have been farming the land for thousands of years, cultivating the soil to grow crops and rearing animals for food and transport. Traditionally, the land is "rotated" to ensure that the soil can rest after use. However, to meet the demands from an ever-growing population, it has been necessary to reduce the amount of time during which land is left fallow. As a result, the soil has become degraded, and in some cases unable to support cultivation.
Continual growing of crops in soil depleted of nutrients is often combined with over-grazing by domesticated animals such as goats, cattle, sheep and camels, as well as cutting down trees and shrubs for fuel. This can have disastrous effects on the fragile desert ecosystem, removing all the natural vegetation cover, and exposing what little soil is left to the ravages of wind, rain and sun. Soil and plants have a two-way relationship in which neither can survive without the other. Most plants need soil in which to root. This anchors them to the ground and stops them being blown away, whilst also providing them with essential water and nutrients. Soil is dependent upon plants for two main reasons. First, plants provide most of the material from which new soil is made, and second, plant roots help to hold the soil together and prevent it from being eroded by the wind and rain.
The climatic extremes of the deserts make them extremely fragile ecosystems. With such a small amount of water available to support wildlife, any disturbance is potentially disastrous. All ecosystems exist in a more or less delicate balance, and the desert is perhaps the most extreme case. With all forms of life linked to one another, a change in the availability of water can affect the smallest plants and the largest animals alike.
photo courtesy of WWF-UK