Area Changes in U.S. Forests and Other Major Land Uses, 1982 to 2002, With Projections to 2062

This study updates an earlier assessment of the past, current, and prospective situation for the Nation’s land base. We describe area changes among major land uses on the U.S. land base for historical trends from 1982 to 2002 and projections out to 2062. Historically, 11 million acres of forest, cropland, and open space were converted to urban and other developed uses from 1992 to 1997 on nonfederal land in the contiguous United States. The national rate of urbanization increased notably compared to the 1982-92 period. The largest percentage increase was in urban use, which grew by 10 percent or 7.3 million acres between 1997 and 2001. Forest land was the largest source of land converted to developed uses such as urbanization. Urban and other developed areas are projected to continue to grow substantially, in line with a projected U.S. population increase of more than 120 million people over the next 50 years, with population growth the fastest in the West and South. Projected increases in population and income will, in turn, increase demands for use of land for residential, urban, transportation, and related uses. Area of nonfederal forest-land cover in the United States is projected to decline over the next half-century, with a 7-percent reduction by 2062. Projected increases in urban and developed uses will likely intensify competition for remaining land between the agricultural and forestry sectors. Reversions to forest land have generally been from grassland used as pasture. All three major land use classes—cropland, forest land, and grassland—have lost area to urbanization, and that trend is projected to continue.

本研究更新了一项针对美国全国土地资源的既往评估，涵盖其历史、现状与未来态势，同时阐述了1982年至2002年美国全国土地资源主要用地类型的面积变化历史趋势，并对至2062年的用地情况进行了预测。1992年至1997年间，美国本土（contiguous United States）的非联邦土地（nonfederal land）上，共有1100万英亩的森林、耕地与开放空间被转为城市及其他开发用地。与1982年至1992年的时段相比，全国城市化速率显著提升。城市用地的增幅占比最高，1997年至2001年间，其面积增长了10%，共计730万英亩。林地是转为城市化等开发用地的最主要土地来源。预测未来50年，美国人口将增长超1.2亿，其中西部与南部地区人口增速最快；与之匹配，城市及其他开发用地面积将持续大幅增长。预计人口与收入的增长将进一步推高住宅、城市、交通及相关用地的需求。未来半个世纪，美国非联邦林地覆盖面积预计将呈下降趋势，至2062年将减少7%。城市与开发用地的预计增长或将加剧农业与林业部门之间的剩余土地竞争。转为林地的土地通常源自作为牧场使用的草地。耕地、林地与草地这三大主要用地类型均因城市化出现了面积缩减，且该趋势预计将持续下去。