据调查 ,2 0世纪五六十年代 ,我国土地荒漠化每年以 15 60ｋｍ2 的速度扩展 ,80年代每年扩展 2 10 0ｋｍ2 ,到 90年代每年扩展 2 4 60ｋｍ2 ,近年扩展速度还在加快。记者 8月 15日从国家林业局获悉 :以防沙治沙为重点的三北防护林四期工程规划目前已获批准 ,以三北地区为重点的 According to the survey, in the 1950s and 1960s, the land desertification of our country expanded at an annual rate of 15 60 km2, with an expansion of 2 10 km2 each year in the 1980s and an annual expansion of 24 60 km2 in the 1990s. The expansion rate in recent years is still accelerating. Reporters learned from the State Forestry Administration on August 15: The plan for the Phase III of the Three North Shelterbelt, which focuses on desertification prevention and control, has now been approved with a focus on the Three North regions