• Defination

You probably think of the desert as a huge area of sand under the scorching sun.

However, not all deserts are like that, since some are located in very cold regions of the planet. Not all deserts are made of sand, either-some are rocky, and others can be formed by salt or ice. But, all deserts do have one thing in common: they are regions that almost continuously suffer from drought, so little moisture that clouds do not formed-that is why the desert sky is almost clear and bright, which means that the ground is always exposed to the direct actiion of the Sun's rays.

The air's temperature can reach 100 to 120 degrees Fahrenheit, and the surface temperature between day and night cause the rocks to break until they form fragments that are so small that the wind carries them away.

Source: Llamas, Andreu, "The incredible world of plants; plants of the deserts|", Chelsea House Publishers, New York, 1996. pp. 4-5.

• Desertification

Desertification refers to the formation of deserts when land loses its productivity and becomes bare. in the last three decades, researchers have noticed that the total area covered by deserts has been increasing by as much as 200 000 square kilometers each year. This is about 300 times the land area of Singapore! It has been estimated that a third of Asia and a fifth of Africa, including land that is currently being farmed, are in danger of becoming deserts.

It was previously thought that desertification occurs along the edge of deserts, expanding the desert area. However, recent studies have shown that desertification can occur in semi-arid areas anywhere in the world, including places far from existing deserts. Semi-arid areas receive an annual rainfall of 250 to 500 millimeters. This amount of rain is sufficient to support vegetation such as grasses, scrubs and small trees.

Source: Secondary Two Textbook, Ministry of Education, Curriculum Planning, Singapore..

• Cause of Desertification

Human Actions

In the past, semi-arid areas were mostly inhabited by small groups of nomads. These people moved around with their herds of animals, never staying at one place for very long. Their constant movement prevented the land from being exhausted. However, in recent decades, the population in semi-arid areas has been increasing. This has caused problems such as overgrazing, over cultivation and deforestation.

Overgrazing refers to the rearing of too many animals on a piece of land The animals eat up all the vegetation, trample on the ground and prevent new vegetation from growing. Without vegetation to act as a protective cover for the soil loses its productivity. In semi-arid areas, the rearing of animals such as cattle and goats in large numbers removes what little vegetation there is and exposes the soil to erosion by wind, creating a desert.

Over cultivation means growing many crops continually on a piece of land without allowing the land to be left fallow. Soil generally needs a fallow period of four to five to recover its nutrients. However, in order to meet the needs of an ever-increasing population for food, people have been growing crops continually in semi-arid land without giving the land enough time to recover. Such intensive farming of the land yields more crops initially, but the land is not suited to such use and its nutrients are soon depleted. Overcultivation of the land eventually results in the formation of a desert.

Source: Secondary Two Textbook, Ministry of Education, Curriculum Planning, Singapore..