Change of Land Degradation in South China and Impacts of Human Activities
中国南方地区土地退化动态变化及人类活动影响

Three pilot areas are chosen for study on temporal change of land degradation in South China. Based on criteria for land degradation assessment an interpretation of land use, vegetation, surface material and erosion morphology is made by using aerial photos of two periods, and with the help of GIS an assessment of land degradation is carried out by using Fuzzy model. Comparison of land degradation maps between 1950's and 1980's shows that changes of land degradation are different from one area to another because of differences of human activities. In the mountain area slightly affected by human activity very slightly degraded land markedly increases due to soil conservation and the remained degraded land tends to decrease from 1950's to 1980's. The reverse situation happens in the area heavily affected by human activity and morphologically characterized by lower undulating hills. Development of land degradation there manifests itself as drastic reduction of non degraded land and severely and very severely degraded land as well as increases of slightly and moderately degraded land. In the low mountain and hill area moderately affected by human activity some increase of moderately degraded land is observed at the expense of marked decrease of non degraded land. It is proved that the changes of land degradation are mainly attributed to reclamation of land and depletion of vegetation led by adverse human activities. In South China most severe land degradation has taken place neither in the mountain area slightly affected by human activity nor in the area heavily affected by human activity and morphologically characterized by lower undulating hills but in the low mountain and hill area moderately affected by human activity.