近50年来中国北方沙漠化土地的时空变化

中国北方在过去的近50年里，沙漠化土地以其广泛的分布和迅速发展构成了区域主要的环境和社会经济问题。遥感监测和评价结果表明，到2000年沙漠化土地已达到 38.57×104 km₂，其中潜在和轻度沙漠化土地13.93×104 km₂，中度沙漠化土地9.977×104 km₂，重度沙漠化土地7.909×104km₂，严重沙漠化土地面积 6.756×104 km₂，它们主要分布在农牧交错带及其以北的草原牧业带、半干旱雨养农业带和绿洲灌溉农业与荒漠过度带。对上世纪50年代后期、1975年、1987年和2000年沙漠化土地遥感监测结果进行对比分析显示，我国北方沙漠化土地自20世纪50年代后期以来一直处于加速发展的态势，沙漠化土地年均发展速率20世纪50年代到70年代中期为1 560 km₂，1976年到1988年提高到2 100 km₂，1988年到2000年之间达到3 600 km₂。“整体恶化，局部治理”是近50年来北方沙漠化土地的变化的基本趋势。沙漠化土地的迅速发展不仅使中国北方的生态环境面临严峻的挑战，而且将严重影响中国整个区域国民经济的发展以及人民生活水平的提高。

Spatial-temporal Changes of Sandy Desertified Land During Last 5 Decades in Northern China

Sandy desertification is a major kind of land desertification in the world. According to our research and practice on land degradation in northern China for nearly 30 years, we define the sandy desertification is land degradation mainly resulted from the human impacts through wind erosion in the arid, semiarid and sub-humid regions in northern China. The results of monitoring, based on remote sensing and GIS, show that the total area of sandy desertified land was 38.57×104 km₂ in 2000, of which the slight and potential lands were 13.93×104 km₂, moderate land was 9.977×104 km₂, severe and very severe lands were 7.909×104 km₂ and 6.756×104 km₂. The sandy desertified land is mainly distributes in the interlacing agro-pastoral region, grassland, semiarid rainfed cropland and oasis irrigated cropland regions. To compare the analytical results of remote sensing data in the late 1950s, 1975, 1987 and 2000, we summarize that the development of sandy desertified land in northern China had been accelerated for the last 5 decades, as its annual expanded rate was 1 560 km₂ during the late 1950s and 1975, 2 100 km₂ between 1975 and 1987 and 3 600 km₂ from 1987 to 2000. The whole situation of sandy desertification comes to depravation and only part of it had been controlled. While most parts of regions had been suffered continually by the spread of sandy desertified land, some desertified areas in the interlacing agro-pastoral region and rainfed cropland region had been improved to be avail farmland and grassland resulted from favorable policy and patterns of landuse, which proved that the process of sandy desertified land could be managed when the fashion and intension of landuse come to be reasonable.