我国北方的土地利用与沙漠化

沙漠化已成为我国北方地区一个重大的环境和社会经济问题。土地利用的方式和程度是沙漠化发展或逆转的主导因素。人类经济活动强度的增加和范围的扩大,造成北方地区农牧交错带的逐渐北移,大面积土地利用方式的改变和地表植被覆盖的减少,使得以风沙活动为主导外营力的沙漠化过程得以发展。我国北方地区近５０年来的土地沙漠化面积不断扩展,已达近３５万ｋｍ２,其蔓延的速率呈加快的趋势。据历史资料分析、野外调查和遥感动态监测与评价,对典型沙漠化地区的土地利用与沙漠化过程的发展及其防治开展了深入的研究。

Landuse and sandy desertification in Northern China

Land sandy desertification is one of the most serious environmental and so cial economic problems in Northern China.The processes of desertification mainly have being controlled by the interaction of human activities and fragile eco environment,which means the pattern and intension of landuse are major factors for development or reverse of desertification.Since the increase of human impact on landuse which had been forced by the increasing pressure of population,the farming pastoral transitional zone in Northern China has been moving towards north,resulting in changes in landuse structure from grazing to cropping to a large extent and destruction of natural vegetation cover.Consequently,wind erosion induced desertification process got accelerated.According to statistics of desertified land areas with different landuse purposes,human activities related sandy desertification were grouped as over cultivation(25%),over grassing(28%),excess firewood gathering(32%) and mis used water resources(8%).During the last 5 decades,sandy desertified land has expanded continually in Northern China,where total area has exceeded 350,000km2 by the mid 1990s.Based on remote sensing monitoring,we found that the growth rate of desertified land has being increased decade by decade,such as the annual average spread area had increased from 1,560km2 between the 1950s to the mid 1970s,to 2,100km2 between the mid 1970s to the late 1980s,to 2,460km2 in the last decade.But some successful models in combating desertification have proved that where the reasonable landuse practice has been adopted over certain years,the sandy desertified land has would get reversed and can be used again for more effective farming or graszing.