为了改善我国北方地区的自然条件,改变林业不适应实现四化建设的落后面貌,党和国家决定在西北、华北北部、东北西部(简称三北)营造防护林体系工程。三北防护林工程因为规模浩大,位于祖国北部边疆,所以被称为绿色万里长城。它根据各地不同的自然条件和灾害特点,因地制宜地营造各种防护林,做到紧密结合基本农田和基本草牧场建设,用材、薪炭和经济林结 In order to improve the natural conditions in the northern part of our country and to change the backwardness of forestry in meeting the four modernizations, the party and the state decided to create a shelterbelt project in the northwestern part, northern part of North China and western part of Northeast China. The Three North Shelterbelt project is known as the Green Great Wall because of its vast scale and its location in the northern frontier of the motherland. It is based on different natural conditions and disasters in different places, according to local conditions to create a variety of shelterbelts, in close connection with basic farmland and grassland construction, timber, firewood and economic forest knot