A third of the earth land surface experiences desert or semi desert condition. However , desertifation is on the rise due to human factors like deforestation .
The basic fact responsible for the existence of deserts is the aridity which is expressed in terms of the scantiness and scarcity of vegetation cover.
Again , another promient feature of a desert is the absence of water .
Because of the foregoing factors , the population is not usually highly concentrated around desert lands . New technology of planting through green houses and genetically modified plants have shown promises. They can grown in semi arid regions.