A man-made desert is not fantastic as it sounds. Two major factors are believed to account for the growth of man-made deserts. One is that the borders of desert in arid or semi-arid regions are extended far beyond the natural true desert into more humid climates due to the heavy grazing and cultivation by man. The other one is that the operation of mankind’s exploitative and destructive activities has brought enormous wastage of soil resources with rapid sloping runoff.

The great enemy of the human race is soil erosion, which has been associated with the habitations of man since before the dawn of history. The histories of human civilizations tell us that buried civilizations is man-made, more than climatic change. According to archaeologists the Sahara, the Central Asian deserts, arid parts of Palestine, Mesopotamia and the Gobi and North China were once prosperous with human life.

As background factors, climatic changes and geologic erosion are long processes affecting human habitations, compared to the history of human society. Comparatively, accelerated erosion, in which soils are washed away far in excess of possible soil formation, can make a mass of loss of soil resources within short time. The accelerated erosion is direct result of destroying the protective vegetation covering of soils. The fertile topsoil is rapidly washed away, or blown off, and then the land productivity reduces until cultivation is abandoned. The decadence of civilizations of North China and Mayan has been attributed to man-induced soil erosion and its consequences in increased run-off.

It is evident that man-made deserts have occurred in the past and are still in progress. We Americans boast of a modern civilization and its progress, but we have been following suicidal methods in treatment of soil resources.

Climate does change, but not an the comparatively rapid rate of the decadence of vast areas of habitable regions. Fortunately，experimental studies have given a better understanding of how deserts may be man-made. And we may put into effect measures adequate to the conservation of soil resources and its productivity and its sustainable utilization.