DESERT

Deserts are regions that receive very little precipitation — an average annual rainfall of less than 250 millimetres (10 inches). They cover more than one third of the world’s land area. This does not mean that this huge land area is barren and lifeless. Rather, deserts have high biodiversity!
The flora and fauna are well-adapted to the harsh conditions. The plant cover is sparse but enormously diverse. Most plants are drought and salt tolerant (like Xerophytes). Cold deserts mainly have grasses and shrubs. All of them, including the animals, play a vital role in maintaining balance in this delicate ecosystem.
This means deserts are not bad but crucial in sustaining the balance in nature. Then how can desertification be a threat to environment?
Well, because desertification is not the expansion of existing deserts. The presence of a nearby desert has no direct relationship to it! It is the degradation of a formerly productive land, where crops could have been grown. And unlike deserts, ‘desertified’ land can support no vegetation — it is infertile and devoid of life.

DESERTIFICATION
Landforms like mountains separate deserts from the surrounding less arid areas. In some areas, the desert borders gradually change to a more humid environment. These transition zones have very fragile ecosystems. The degradation of lands in these arid, semi-arid, and dry subhumid areas is called Desertification.
For example, seven thousand years ago the Thar Desert received abundant rainfall, hosted shrubs and trees like Jamun, and had rivers and lakes! So how did the fertile Thar turn to thorns? Because of us! And to a very small extent due to climatic variations.

Human activities
Humans settle on productive lands to grow crops and graze livestock. But, over-farming and over-exploitation of resources like groundwater diminishes the fertility of the lands. Deforestation and over-grazing add to the trouble by reducing the lands’ tree cover. The soil is exposed to wind and water causing soil erosion. When this topsoil is eroded, the salts present in the land come up to the surface, preventing further growth of the trees. This is called salinisation (as evident in the Rann of Kachchh). The conditions are worsened by rapid urbanisation, industrialisation and poor land management systems.

Natural
Sand dunes, moving with wind, may cause desertification. In a major dust storm, dunes may move tens of metres! For example, linear dunes of the Sahara Desert encroach on Nouakchott, the capital of Mauritania in northwest Africa.
Some climatic changes may even be set off by land degradation caused by human activities.
Droughts do not cause desertification. Well-managed lands can recover from it when rains return. However, land abuse during droughts can cause land degradation.

And…
The outcome is clear — loss of the rich biodiversity and the productive capacity of the entire area, leading to massive displacement of people. Over 250 million people are directly affected by desertification, and some one billion people in over one hundred countries are at risk (Source: United Nations Convention to Combat Desertification).