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.

本研究对美国国土基底的过往、当前及未来态势的早期评估进行了更新。本研究针对1982年至2002年的历史趋势，以及截至2062年的未来预测，阐述了美国国土基底上主要土地利用类型的面积变化情况。1992年至1997年间，美国本土非联邦土地上共有1100万英亩的森林、农田与开阔空间被转为城市及其他开发用途；相较于1982-1992年时段，全国城市化增速显著提升。1997年至2001年间，增幅最为显著的土地利用类型为城市用地，其规模增长10%，即增加730万英亩。林地是转为城市化等开发用途的最大土地来源。据预测，城市及其他开发区域将持续大幅扩张，这与未来50年美国人口预计增长超1.2亿的趋势相符，且人口增长最快的区域为西部与南部地区。人口与收入的预计增长将进一步推高住宅、城市、交通及相关用途的土地需求。未来半个世纪内，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%。城市及开发用地的预计增长可能会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来自作为牧场使用的草地。三大主要土地利用类别——农田、林地与草地——均因城市化出现面积缩减，且该趋势预计将持续下去。