Fill in each numbered blank with one suitable word or phrase.

More than a billion people all over the world are (1) _____  the threat of desert expansion, but few of them are aware that they themselves cause it and are also its (2)___. People cut (3) ____ trees for fuel and farmland. Their herd eat (4) _____ the grass covering valley floors and hillsides. The climate and soil quality, therefore, are affected and forests are turned into (5) ____.

In some places, many people had to leave their homes when their wells became dry and sand buried their houses and crops. Therefore, government in nearby areas have had local people (6) ____ trees and banned burning firewood for fuel. Many techniques have been (7) _____. For example, in Iran, a thin covering of oil was poured on Sandy areas to retain (8) _____ for planting trees, but this method may harm the environment. Other countries built long canals or pipelines (9)____ water to desert areas. Unless people find more (10) _______ methods, their homes and land will be lost. The last against the desert is continuing.

Many techniques have been (7) _____.