Introduction

The U.S. Geological Survey (USGS), with support from NatureServe, 

has modeled the potential distribution of 419 terrestrial ecosystems for the 

conterminous United States using a comprehensive biophysical stratification 

approach that identifies distinct biophysical environments and associates them 

with known vegetation distributions (Sayre and others, 2009). This standardized ecosystem mapping effort used an ecosystems classification developed by 

NatureServe (Comer and others, 2003). The ecosystem mapping methodology 

was developed for South America (Sayre and others, 2008) and is now being 

implemented globally (Sayre and others, 2007). The biophysical stratification 

approach is based on mapping the major structural components of ecosystems 

(land surface forms, topographic moisture potential, surficial lithology, isobioclimates and biogeographic regions) and then spatially combining them to 

produce a set of unique biophysical environments.

These physically distinct areas are considered as the fundamental structural units (“building blocks”) of ecosystems, and are subsequently aggregated 

and labeled using the NatureServe classification. The structural footprints were 

developed from the geospatial union of several base layers including biogeographic regions, isobioclimates (Cress and others, 2009a), land surface forms 

(Cress and others, 2009b), topographic moisture potential (Cress and others, 

2009c), and surficial lithology (Cress and others, in press). Among the 49,168 

unique structural footprint classes that resulted from the union, 13,482 classes 

met a minimum pixel count threshold (20,000 pixels) and were aggregated into 

419 NatureServe ecosystems using a semiautomated labeling process based on 

rule-set formulations for attribution of each ecosystem.

The resulting ecosystems are those that are expected to occur based on the 

combination of the bioclimate, biogeography, and geomorphology. Where land 

use by humans has not altered land cover, natural vegetation assemblages are 

expected to occur, and these are described in the ecosystems classification. The 

map does not show the distribution of urban and agricultural areas—these will 

be masked out in subsequent analyses to depict the current land cover in addition to the potential distribution of natural ecosystems. 

This map depicts the smoothed and generalized image of the terrestrial 

ecosystems dataset. Additional information about this map and any data 

developed for the ecosystems modeling of the conterminous United States 

is available online at: http://rmgsc.cr.usgs.gov/ecosystems/.

References Cited:

Comer, Patrick, Faber-Langendoen, Don, Evans, Rob, Gawler, Sue, Josse, 

Carmen, Kittel, Gwen, Menard, Shannon, Pyne, Milo, Reid, Marion, 

Schulz, Keith, Snow, Kristin, and Teague, Judy, 2003, Ecological systems 

of the United States—A working classification of U.S. terrestrial systems: 

NatureServe, Arlington, Va. (Available online at http://www.natureserve.

org/library/usEcologicalsystems.pdf. 

Current descriptive information for ecological types found at http://www.

natureserve.org/explorer/.)

Cress, J.J., Sayre, Roger, Comer, Patrick, and Warner, Harumi, 2009a, Terrestrial ecosystems—Isobioclimates of the conterminous United States: 

U.S. Geological Survey Scientific Investigation Map 3084, scale 

1:7,000,000.

Cress, J.J., Sayre, Roger, Comer, Patrick, and Warner, Harumi, 2009b, Terrestrial ecosystems—Land surface forms of the conterminous United 

States: U.S. Geological Survey Scientific Investigation Map 3085, scale 

1:5,000,000.

Cress, J.J., Sayre, Roger, Comer, Patrick, and Warner, Harumi, 2009c, Terrestrial ecosystems—Topographic moisture potential of the conterminous 

United States: U.S. Geological Survey Scientific Investigation Map 3086, 

scale 1:5,000,000.

Cress, J.J., Soller, David, Sayre, Roger, Comer, Patrick, and Warner, Harumi, 

in press, Terrestrial ecosystems—Surficial lithology of the conterminous 

United States: U.S. Geological Survey Scientific Investigation Map, scale 

1:5,000,000.

Sayre, Roger, Yanosky, Alberto, and Muchoney, Doug, 2007, Mapping global 

ecosystems—The GEOSS approach, in Group on Earth Observations, ed.: 

London, U.K., Tudor Rose, p. 231–232. (Also available online at: http://

www.earthobservations.org/docs_pub.shtml.)

Sayre, R., Bow, J., Josse, C., Sotomayor, L., and Touval, J., 2008, Terrestrial 

ecosystems of South America, in Campbell, J.C., Jones, K.B., and Smith, 

J.H., eds., North America land cover summit—A special issue of the 

Association of American Geographers: Association of American Geogra‐

phers, p. 131–152. 

Sayre, R.G., Comer, P.J., Warner, H., and Cress, J.J., 2009, A new map of 

standardized terrestrial ecosystems of the conterminous United States: 

U.S. Geological Survey Professional Paper 1768, 17 p. (Also available 

online at http://pubs.usgs.gov/pp/1768.)

Forest and woodland ecosystems

Herbaceous ecosystems

Shrubland ecosystems

Steppe/savanna ecosystems

Woody wetland ecosystems

Herbaceous wetland ecosystems

Sparsely vegetated ecosystems

Unknown

Water

State boundaries

EXPLANATION

Terrestrial Ecosystems Groups

Terrestrial Ecosystems of the Conterminous United States

By Roger Sayre, Patrick Comer1, Jill Cress, and Harumi Warner2

2010fdsasdfa

Scientific Investigations Map 3106

Version 1.0

U.S. Department of the Interior

U.S. Geological Survey

Publishing support provided by:

Denver Publishing Service Center

Manuscript approved for publication on December 18, 2009

For more information concerning this publication, contact

USGS Central Region Geospatial Information Office

Federal Center

Box 25286

Denver, CO 80225

1-888-ASK-USGS or

Jill Cress

Rocky Mountain Geographic Science Center

U.S. Geological Survey

(303) 202-4275

jjcress@usgs.gov

Any use of trade, product, or firm names is for descriptive purposes only

and does not imply endorsement by the U.S. Government.

Although this information product, for the most part, is in the public

domain, it also contains copyrighted materials as noted in the text.

Permission to reproduce copyrighted items for other than personal use

must be secured from the copyright owner.

For sale by U.S. Geological Survey Information Services

Box 25286, Federal Center, Denver, CO 80225

1-888-ASK-USGS

This and other USGS products are available on the World Wide Web at:

http://store.usgs.gov/

This report is available at

http://pubs.usgs.gov/sim/3106

1 Ecology Department, NatureServe, Boulder, Colo.

2 Parallel Inc., Lakewood, Colo.

Prepared in collaboration with NatureServe

Suggested citation:

Sayre, Roger, Comer, Patrick, Cress, Jill, and Warner, Harumi, 2010, Terrestrial

ecosystems of the conterminous United States: U.S. Geological Survey Scientific 

Investigations Map 3106, scale 1:5,000,000, 1 sheet.

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