Earth Science: Surviving Drought Conditions
Deserts may be barren, but they are nonetheless home to many plants and animals-both during the long droughts, and when there is a short-lived sea of flowers after a rare rainfall.
Numerous desert inhabitants have developed amazing survival strategies in such dry, inhospitable environments. Many trees and bushes produce long roots in order to reach the groundwater available at great depth. In order to minimize evaporation, plants breathe at night.
They have a reduced leaf surface area, carry thorns instead of leaves, or exist merely as a stem, like cacti or some members of the spurge family (Euphorbiaceae). In the Australian eucalyptus, the glaring sun light is reflected by a wax layer, or in tamarisks and some palm trees, by salt excretions.
In order to utilize the precious liquid wisely, some succulents have developed large-cell storage tissue in their leaves, such as living rocks (Aizoaceae); in stalks, such as saguaros; or in stems, such as aloe trees. Some plants bridge extreme drought periods, by resting in the ground as seeds. When sufficient rainfall returns they go through their entire life cycle in an extremely short period of time.
Desert animals
Desert fauna also displays conspicuous adaption to extreme environ- mental conditions. For example, the ability to move rapidly and long legs aid in protecting them against heat reflecting from the ground below. Often they also have a reduced water metabolism. Ants and rodents get their moisture from seeds.
They in turn become a source of food and water for lizards, snakes, and jackals. Other animals obtain water directly, such as the dew-drinking black beetle from the Namib, or antelope herds, which undertake long migrations to water holes.
Fertile islands
The most active life in the desert is found in the oases. These fertile islands are located where water comes to the Earth’s surface. Many oases develop around artesian wells, where water rises to the surface under its own pressure. Some of these wells are fed from ground-water, others with water from artificial lakes or reservoirs or a remote river.
The area around an oasis is usually densely populated and intensively cultivated. The tree most characteristic of oases is the date palm, which originally came from North Africa and India.
DESERTIFICATION
In regions with a relatively dry climate, intensive human cultivation can have terrible consequences, reducing vegetation, draining water sources, and causing soil erosion and salinity.
The formation of deserts threatens the existence of more than a billion people in over a hundred countries. In Africa, millions have died in the famines caused by the severe desertification occuring there.