USGS - science for a changing world

Land Cover Database Details State of the Land: Lower 48 described with
Census-like accuracy
Released: 3/19/2007

The U.S. Geological Survey and the federal interagency Multi‑Resolution
Land Characteristics Consortium (MRLC) recently announced the completion
of a massive database that describes the land surface condition of each
30-meter cell of land in the conterminous United States. Nearly six such
cells - each 98 feet long and wide - would fit on a football field. The
2001 National Land Cover Database (NLCD 2001) and its products are
available at http://www.mrlc.gov/.

Land cover is broadly defined as the biophysical pattern of natural
vegetation, agriculture, and urban areas. It is shaped by both natural
processes and human influences. NLCD 2001 data portrays 16 classes of
land cover in the lower 48 states, the percent of tree canopy, and the
degree of surface imperviousness in urban areas.

"Just as the U.S. Census is fundamental in assessing patterns of
national population growth, we also require an authoritative, periodic
review of land conditions ‑ a Census of the Nation's Land Resources ‑ to
understand how people and the land interact," said USGS Director Mark
Myers. "The National Land Cover Database gives us that. It's a
versatile, balanced look at the state of the land."

Based on satellite imagery taken in 2001, the broad, yet precise
database was constructed in a six‑year collaborative effort by the 11
MLRC agencies (www.mrlc.gov). The range and accuracy of information in
the database enables managers of public and private lands, urban
planners, agricultural experts, and scientists with many different
interests (for instance, climate change or invasive species) to identify
critical characteristics of the land for a wide variety of investigations.

"With a growing population of more than 300 million people and the
challenging prospect of climate change, comprehensive information about
the condition of our land resources becomes more and more vital," said
Barbara Ryan, USGS Associate Director for Geography. "Land cover
information is essential for understanding a wide variety of issues: for
example, ecosystem status and health; spatial patterns of biodiversity;
land use planning; and land management policy."

NLCD 2001 is a second generation effort to update the Nation's land
cover information. The first NLCD was completed in 2000 with imagery
acquired around the year 1992. Information from NLCD 1992 has been used
in thousands of applications in the private, public, and academic
sectors ‑ applications that range from helping to site cell phone towers
to tracking how diseases spread.

The national consistency of NLCD information makes possible the
sweeping, contextual analysis of national land perspectives, such as the
Heinz Center's State of the Nation's Ecosystems, the Environmental
Protection Agency's Draft Report on the Environment, the USGS National
Water Quality Assessment, and the Landfire Program (a federal
interagency program to predict and mitigate wildfire). Complete, updated
coverage of NLCD 2001 data for Alaska, Hawaii, and Puerto Rico is
expected to be available by December 2007.

NLCD products are web enabled for download from the MRLC website at
www.mrlc.gov. USGS is currently working with private software developers
to create publicly available, user friendly tools that can be used to
conduct web-based geospatial analyses of NLCD. Future nationwide updates
of NLCD 2001 will continue to monitor land cover change across the Nation.


Contact Information:
U.S. Department of the Interior, U.S. Geological Survey
Office of Communication
119 National Center
Reston, VA 20192 Denver Makle - [log in to unmask]
Phone: 703-648- 4732

Collin Homer - [log in to unmask]
Phone: 605-594-2714