Forests cover four billion hectares (31%) of the Earth’s landmass and contain over 75% of all carbon in vegetation. They provide renewable raw materials and natural amenities, protect land and water resources, harbor biological diversity, and mitigate climate change. However, due to less precipitation, the forest coverage rate is only 5.86% in Northwest China. The forests in these arid areas are mainly distributed in alpine areas, which play a key role in runoff regulation and ensure the ecological and economic development of the middle and lower reaches of the inland basins. In the past several decades, China had experienced large-scale deforestation and reforestation. What were the changes of the few forest areas and growing stock in arid Northwest China? Has forest quality been restored? Changes of that had been analyzed in this article. The results showed that the forest area and growing stock decreased greatly from the 1950s to 1970s; the artificial forest area increased clearly; the natural forest area stabilized from the 1980s, growing stock of forest per unit area was still lower than that in the 1950s; and the forest quality had not yet been restored. Results of the analysis of influencing factors showed that the policy-led human activities in different periods were the efficient cause of forest changes in Northwest China. With the development of forestry science, more and more attention has been paid to forest ecological restoration. “Three-North Shelter Forest Program (TNSFP)” in 1978 had made great progress on forest areas by afforestation, and the ecological benefits and economic benefits also increased remarkably owing to the increase in the artificial forest area. In recent years, great progress on forest areas has been made by afforestation, and the forests also contribute significantly to the ecology and economy. However, large-scale afforestation in the Loess Plateau had caused a phenomenon of large investment and little effect on water conservation in some afforestation areas, which showed that afforestation initiated under different polices, which were not always scientifically based, resulted in unintended consequences. Clear ecological principles should be used to ensure best environmental and forest ecology outcomes.

根据1975-2018年民勤绿洲土地沙漠化分类体系及遥感影像数据,探究了民勤绿洲沙漠化时空变化过程;选取影响绿洲沙漠化的自然与人为驱动因子,运用主成分分析方法定量评价了民勤绿洲沙漠化过程的主要驱动力.结果表明:1975-2018年沙漠化程度以重度沙漠化为主,轻度、中度、重度和严重沙漠化面积均呈减少趋势,以2000年为界表现为先发展后逆转趋势;1975-2000年,轻度、中度、重度沙漠化重心总体向东北方向迁移,严重沙漠化的重心向西迁移,沙漠化有向绿洲东北部和巴丹吉林沙漠发展的趋势;2000-2018年轻度沙漠化的重心向西北方向迁移,中度、重度和严重沙漠化重心相对稳定,绿洲沙漠化发展得到明显控制.在绿洲沙漠化过程中,人为因素贡献率为39.53％,自然与人为综合贡献率为26.58％,自然因素贡献率为10.77％,人为因素是民勤绿洲沙漠化的主要驱动力.水资源极度匮乏是绿洲沙漠化的决定因素,在以后的防沙治沙工作中,合理调控人类的生产经营活动,优化干旱区水资源配置,可从源头上治理民勤绿洲的沙漠化.