ABSTRACT
Rocky desertifi cation is the deterioration of land in fragile karst areas with semitropical climates. Due to unfavorable natural conditions and unchecked human activities, the ground surface takes on the appearance of a barren landscape with little vegetation after the topsoil is eroded and dissolved away. With increasingly severe erosion, the soil becomes less productive and under extreme conditions, only rock remains. At present, rocky desertifi cation in the mountainous Southwest of China is an urgent environmental problem that not only constrains local development, but also has a long distance negative impact by causing heavy soil erosion as far away as the middle and lower reaches of the Yangzi River. Many factors can cause rocky desertifi cation, but the main factors are the type of bedrock, precipitation, topography and human activities. The clearance of primeval forest and grassland for cultivation, resulting from an increasing population, is one of the major human causes of rocky desertifi cation. The cultivation of New World food crops such as maize, sweet potato and other root crops since the early Qing Dynasty, on ground that was unsuitable for rice, wheat and other native crops, had long-term environmental consequences. Once soil originally covered with forest and grassland was cultivated, the soil structure was altered. It became loose and thus vulnerable to soil erosion. Moreover, the extensive cultivation of new crops attracted immigrants, and expanding populations increased demand for these high-yield crops, further intensifying land use. As a result, there is a positive correlation between crop cultivation and population increases.
