The Changing Landscape of the Eastern United States

By Thomas Loveland and Roger Auch

National Land Cover Database: The National Map shows the patterns and amounts of the land cover spanning the conterminous United States. About 28 percent of the nation is forested, 26 percent is in cropland, 17 percent is shrub-covered, and 15 is grass-covered; 3 percent of this area has been urbanized. The last tenth of the land cover is water, wetlands, bare ground, and snow and ice.

The USGS has a rich history of mapping and monitoring the uses of the Nation's public and private lands. John Wesley Powell's late-1800's studies on the topography of the West enabled the settlement and establishment of irrigation agriculture. In the early 1970's, visionary USGS scientists like William Pecora and James Anderson established the capabilities to routinely use instruments on orbiting satellites to map the land use and land cover of the Nation.

Segments of Landsat images covering land near Charleston, WV, show the expansion of coal mining that occurred between 1992 and 2000. The bright areas are the coal mines, and the red colors show the deciduous forests of this part of Appalachia.

The work of Powell, Pecora, and Anderson continues, as USGS staff now use imagery from Earth-orbiting Landsat satellites to periodically map land cover of the nation. The National Land Cover Database, part of The National Map, provides detailed information on the patterns and extent of the Nation's forests, grasslands, shrublands, croplands, urban areas and other land covers.

USGS researchers are working with partners in the U.S. Environmental Protection Agency and NASA to document how the Nation's lands have been changing. This is being done by interpreting the 1972-2001 USGS archive of Landsat images to estimate the rates and types of change. Field surveys are being used to uncover evidence of the driving forces of change. By systematically documenting the rates, causes, and consequences of our ever-shifting and evolving landscape, the USGS research team is providing objective information and knowledge needed for the Nation's economic development and management of natural resources.

Land cover change varies from region to region.

The study of land cover is currently focused on thirteen regions covering much of the Eastern United States. When looked at as a whole, the average annual change in the 13 regions was approximately 0.7 percent of the 450,000-square-mile area; the lowest amount of change occurred in the 1970's (0.5 percent per year), and the most rapid change occurred between 1986 and 1992 (1.0 percent per year).

Since 1972, forests cover decreased from 56 to 54 percent of the area, while the urban landscape expanded by 2 percent to cover an additional 8,800 square miles - or 11 percent of the eastern study area. During this time, nearly 6,600 square miles of cropland was lost. Two-thirds of this loss resulted from farmland converting back to forests, either as timber plantations or because the land's productivity was marginal and no longer needed in modern agricultural production. Approximately 25 percent of the lost eastern farmland is now part of the Nation's urban base.

The fabric of change in the East becomes much more varied when looking at individual regions. Urbanization was the dominant theme in the regions that encompass the Boston to Washington corridor (Northern Piedmont, Atlantic Coastal Pine Barrens, and the Northeastern Coastal Zone), whereas the cyclic nature of industrial forestry caused the major changes in the Southeastern Plains, Mid-Atlantic Coastal Plain, and the North Central Appalachians. Surface coal mining was the major story in the Central Appalachians. A number of ecoregions had combinations of dominant themes. The Piedmont had much timber harvesting and regeneration along with substantial urbanization, whereas the Southwestern Appalachians had coal mining, primarily in the earlier dates, along with southern industrial forestry.

The percentages and rates of change also varied across the ecoregions. The Blue Ridge Mountains, a significant portion in public land, had the least change, at 2 percent over the nearly 30-year period. At the other extreme, nearly 21 percent of the Southeastern Plains changed between 1972 and 2000. The nature of change many times tended to blur the perception that land cover had been altered. Cyclic forest clearing and regeneration may indicate a high rate of change, but many times trees ended up replacing trees. Unidirectional change to urban land uses from agricultural or forest land usually left the land cover altered permanently. This is not to say that one change is more important than another. Each raises its own consequences and, possibly, challenges that may be different for individual ecoregions.

Field observation remains an essential part of the study of landscape change.

The USGS's continuing and evolving ability to map and analyze land cover and land use change is a valuable asset to the Department of the Interior. The research provides relevant scientific information for other DOI agencies and the Nation as a whole.