USGS Releases Detailed Map of Land-Cover in U.S.
The map is available online and also shows the extent of human land-use in the U.S.
"The GAP national land cover data, based on the NatureServe Ecological Systems Classification, is the most detailed, consistent map of vegetative associations ever available for the United States and will help facilitate the planning and management of biological diversity on a regional and national scale.
...The final version of the landcover map contains 551 Ecological Systems and modified Ecological Systems (the modified ecological systems represent 32 land use classes which depict developed and/or disturbed land cover classes). The map combines data from previous GAP projects in the Southwest, Southeast, and Northwest United States with recently updated California data. For areas of the continental United States where ecological system-level GAP data has not yet been developed, data from the LANDFIRE project compiled by Landscope was used. This allows for the construction of a seamless representation of ecological system distributions across the continental United States."