Distribution Data Sources

Plant & Animal Distribution Data
National and Subnational
County and Watershed
Ecological Distribution Data
National and Subnational
MRLC Map Zones
Ecological Divisions

Plant & Animal Distribution Data

National and Subnational Distribution

NatureServe Explorer provides data on United States and Canada geographic distribution by nation, and by Canadian province or U.S. state for plants and animals. The sources of this broad-scale distribution information include scientific literature, museum specimen records, species lists, range maps, external databases, and consultation with experts, including scientists from natural heritage member programs. Each program also maintains finer scale distribution information for the species of greatest conservation concern in its jurisdiction. Questions about distribution within a specific jurisdiction should be directed to the local member program.

For Plants

Plant distribution data in NatureServe Explorer are based on a variety of sources. The state and province distribution records of species shown with corresponding subnational conservation status information (i.e., subnational ranks SX-S5) are based on information received from the respective natural heritage member program. For vascular plants, most other state and provincial records, especially for more common species, were based on distribution information from the Synthesis of the North American Flora (Kartesz 1999). Revisions to those records are made over time in accordance with more recent information. Some distribution records are added from other sources of botanical literature reviewed by NatureServe botanists.

Kartesz JT. 1999. A synonymized checklist and atlas with biological attributes for the vascular flora of the United States, Canada, and Greenland. In: Kartesz JT, Meacham CA. Synthesis of the North American Flora, Version 1.0. Chapel Hill: North Carolina Botanical Garden.

For Vertebrates and Invertebrates

Animal distribution data in NatureServe Explorer are derived from many sources. For vertebrates and certain well-studied groups of invertebrates, the primary sources are scientific literature, web sites, experts, and information from local data centers. Many of the same sources used for taxonomy and nomenclature are consulted for distribution information. In turn, much of the published information is based on museum specimen records and, especially for birds, reliably documented observation records. Review of the available literature and other sources is done by NatureServe zoologists and by other experts contracted to develop this information, who supplement their literature research with personal knowledge. Over time, state and province distribution lists are refined as local data centers obtain new records for species not previously recognized in their jurisdictions and transfer this new information to the NatureServe's central databases during the annual data exchange process. For invertebrates in less well-studied groups, the state and province data in the central databases come from local natural heritage zoologists who derive their knowledge from the sources mentioned above, especially local experts and museum collections.

Tabular County and Watershed Distribution (based on available natural heritage records)

County and watershed distribution data are available for plants and animals listed under the U.S. Endangered Species Act, including those already listed as threatened or endangered and those that are candidates or have been proposed for listing. In addition, distribution data are available for species tracked by the natural heritage network with an emphasis on those species with a NatureServe global conservation status of critically imperiled (G1 or T1) and imperiled (G2 or T2). Data on ecological communities are not currently available at these scales. See below for important caveats about the completeness of these county and watershed distributions.

The county and watershed distribution data based on natural heritage records presented on this site include all U.S. states. In addition, county and watershed data for most animals of Washington are based on data provided by the Washington Department of Fish & Wildlife. The data are based on Element Occurrence (EO) records, precise locality data that are developed and maintained by individual state natural heritage programs¹. The focus of these programs is on collecting data for imperiled species, therefore data is most complete for plants and animals that are imperiled (G1 or G2) and incomplete or non-existent for plants and animals with a NatureServe global conservation status of at-risk or apparently or demonstrably secure (G3 or T3, G4 or T4, G5 or T5). Data for selected species may include information based on historical records. If your search returns no records, then the participating programs have no data available at this website. However, natural heritage biologists have extensive knowledge of plants and animals within their respective jurisdictions; for additional information please contact the appropriate natural heritage program or NatureServe.

In addition to watershed distribution data based on natural heritage records, this site presents maps based on a variety of information sources. See: U.S. Distribution by Watershed for more information. We are always looking to improve the overall quality of our databases. If you have information on a current occurrence of a G1/T1 or G2/T2 ranked plant or animal for a particular county or watershed not indicated on this report, please contact the appropriate natural heritage program (http://www.natureserve.org/natureserve-network).


The following are the dates these data were acquired for each state or provincial program. Due to latency between updates made in state, provincial or other NatureServe Network databases and when they appear on NatureServe Explorer, you may wish to contact the data steward in your jurisdiction to obtain the most current data. Please refer to the NatureServe Network Directory to find contact information for your jurisdiction.

Participating Jurisdiction

Date Data Acquired


September 2015


November 2013


October 2016


September 2007


July 2013


October 2016


October 2016


March 2014


November 2013


September 2015


February 2014


June 2011


May 2015


June 2015


December 2011


September 2015


May 2015


May 2015


April 2015


December 2013


May 2010


January 2015


August 2016


January 2015


November 2015


July 2011

Navajo Nation

August 2013


September 2016


February 2015

New Hampshire

October 2013

New Jersey

June 2010

New Mexico

October 2013

New York

February 2015

North Carolina

December 2013

North Dakota

September 2015


July 2008


December 2013


September 2016


September 2010

Rhode Island

July 2007

South Carolina

November 2013

South Dakota

January 2015


February 2015


January 2014


January 2013


September 2016


January 2015


Plants May 2015; Animals January 2017

West Virginia

September 2015


November 2013


December 2011

Mapped U.S. Distribution by Watershed

For most native, U.S. freshwater fishes and U.S and Canadian freshwater mussels, watershed distribution maps are available. These maps are based on a variety of information sources (i.e. published and unpublished literature, natural heritage element occurrence records, personal communications, etc.) and are generally more complete than what is available in the tabular display of watershed distribution or via the NatureServe Explorer watershed search which are both based only on natural heritage element occurrence records.

Fishes: all native freshwater fishes of the United States, exclusive of Alaska and Hawaii, have been mapped by small watershed. The ranges depicted reflect native ranges. Note that many species, especially sport or commercial species, have been introduced widely. Areas where these species have been introduced are not shown on the maps. Visit the USGS Nonindigenous Aquatic Species database for ranges outside of the native range. The NatureServe data on native freshwater fishes were compiled over a period of several years (1997-2003 and 2007-2010) and represent the most complete distributional information possible for these species at the level of the USGS 8-digit cataloging unit. The maps display both historic-only and current watersheds of occurrence within the native range. These data were derived from the precise location data (element occurrences) compiled by state natural heritage programs, scientific literature, and species experts, representing over 250 different sources. Funding was provided by the Regina Bauer Frankenberg Foundation for Animal Welfare, The Nature Conservancy, Landscope America, the Central Administrative Office of the USDA Forest Service, and the US Geological Survey.

Mussels: all native, freshwater mussels of North America, north of Mexico, have been mapped. These data were compiled over a period of several years (1997-2000 and 2007-2009) and represent the most complete distributional information possible for these species. Extinct, Possibly Extinct, Imperiled and Vulnerable species (NatureServe Conservation Status Ranks of GX, GH, G1, G2, and G3) are mapped by cataloging units (defined as a geographic area representing part or all of a surface drainage basin, a combination of drainage basins, or a distinct hydrologic feature) and utilize USGS 8-digit cataloging units or Canadian sub-sub-drainage areas. The remaining species (NatureServe Conservation Status Ranks of G4 and G5) are mapped by subregions (defined as the area drained by a river system, a reach of a river and its tributaries in that reach, a closed basin, or a group of streams forming a coastal drainage area) and utilize USGS 6-digit accounting units or Canadian sub-drainage areas. The maps display both historic-only and current watersheds of occurrence within the native range. These data were derived from the precise location data (element occurrences) compiled by state natural heritage programs and provincial conservation data centres, scientific literature, and species experts, representing over 450 different sources. Funding was provided by the Regina Bauer Frankenberg Foundation for Animal Welfare, the Southeast Information Node of the National Biological Information Infrastructure, Sears Holding Management Corporation, L.L. Bean, Inc., Limited Brands, Inc. and the Sarah K. de Coizart TENTH Perpetual Charitable Trust.

Analyses of both the fish and mussel data were first presented in the report Rivers of Life: Critical Watersheds for Protecting Freshwater Biodiversity (1998). The analyses were also published in amended form in Precious Heritage: The Status of Biodiversity in the United States (2000).

Changes to these Data

These data are dynamic with new records frequently being added and old records being revised as new information is received. As a result, the information on this website should not be considered a definitive statement on the presence or absence of freshwater fishes or freshwater mussels in any given watershed, nor should be used as a substitute for on-site surveys required for environmental assessments.

In any data set such as this there will be errors of omission as well as errors of commission. We ask users of these data to let us know about such errors so that the data can be improved over time for the future benefit of all users. Comments can be submitted through the Contact Us button above or by email to Bruce Young, Director, Species Science. Please cite the data source for any omissions or changes in status (e.g., current to historic-only). We hope that these data will be a useful tool for aquatic research and analyses and for conservation planning.

¹ An element occurrence is NatureServe's basic unit of record for documenting and delimiting the presence and extent of a species or natural community on the landscape. EOs are defined as an area of land and/or water where a species or ecological community is, or was, present, and which has practical conservation value. Element occurrences for species commonly reflect populations or subpopulations. (For additional details about element occurrences, see NatureServe Core Methodology.)

Distributions for Ecological Communities

National and Subnational Distribution

U.S. state, Canadian province and ecoregional distribution information is an inherent part of the development of both parts of the International Ecological Classification Standard: the International Vegetation Classification, and the International Terrestrial Ecological System Classification. NatureServe ecology staff and other experts review distributional data and assign communities to additional states, provinces, and ecoregions based on their knowledge of the local flora, analyses of vegetation data, and consideration of more qualitative information on vegetation patterns. However, absence of a state, province, or ecoregion from the distributional data cannot be interpreted as a definitive statement that the community does not occur there.


The Nature Conservancy Ecoregions

The Nature Conservancy (TNC) developed a map of "ecoregions" to organize its conservation prioritization work. TNC first delineated ecoregions for the United States in the late 1990s (adapted from Bailey et al.1994), and has now delineated ecoregions for all of North America. For the rest of the world, TNC has adopted World Wildlife Fund (WWF) ecoregions. For more information, see "Conservation By Design". TNC is currently in the process of delineating marine ecoregions for the Western Hemishpere, but NatureServe has not currently attributed any ecological units to the marine ecoregions.

For the United States, plant associations, vegetation alliances and ecological systems have all been attributed to TNC's ecoregions by TNC and NatureServe ecology staff. These data are reviewed and refined continually as vegetation mapping and conservation planning efforts proceed. For Latin America (including Mexico) and the Caribbean, ecological systems have been attributed to the WWF ecoregions, as adopted by TNC. These data will be available in the future on InfoNatura.

United States Forest Service Ecoregions

The U.S.D.A. Forest Service has developed a hierarchical framework, the National Hierarchical Framework of Ecological Units (as described by Cleland et al. 1997), which provides a systematic method for classifying and mapping areas of the earth based on co-occurring ecological factors at different geographic scales. NatureServe has attributed ecological communities in the U.S. to three of these ecoregion levels: Province, Section, and Subsection, with varying degrees of comprehensiveness across the country.

All western* U.S. plant associations and alliances are comprehensively attributed to Sections using Bailey et al. (1994), except in the interior Pacific northwest where the Section boundaries used are those developed by the U.S. Forest Service during the Interior Columbia Basin Ecosystem Management Project. Eastern* U.S. alliances and associations are attributed to Sections and Subsections using Keys et al. (1995): the data are comprehensive for alliances and on a more case-by-case basis for associations, with generally greater completeness for more globally rare associations. This map shows the combined Bailey et al. (1994) and Keys et al. (1995) NatureServe used, as well as the Section boundaries used in the interior Pacific Northwest.

For Ecological Systems, western U.S. systems have been attributed to the USFS Ecomap regions as described by Cleland et al. (2007). The eastern U.S. ecological systems will be attributed during late 2006 and 2007.

*Keys et al. (1995) provide the spatial framework and labeling of the USFS Ecoregional units for the area east of the "dry line." This generally corresponds to 97 degrees West longitude (or roughly just west of a line extending through Fargo, North Dakota, south through Corpus Christi, Texas), and includes Divisions 210, M210, 220, M220, 230, M230, 250 of the Humid Temperate Domain (200) and all of the Humid Tropical Domain (400). For areas west of the dry line, Bailey et al. (1994) provide the spatial framework for Divisions 240, M240, 260, M260 of the Humid Temperate Domain (200) of the west coast of the United States and all of the Dry Domain (300).

Bailey, R. G., P. E. Avers, T. King, and W. H. McNab, editors. 1994. Ecoregions and subregions of the United States (map). U.S. Geological Survey, Washington, DC. Scale 1:7,500,000 colored. Accompanied by a supplementary table of map unit descriptions compiled and edited by W. H. McNab and R. G. Bailey. Prepared for the USDA Forest Service.

Keys, J. E., Jr., C. A. Carpenter, S. L. Hooks, F. G. Koenig, W. H. McNab, W. E. Russell, and M-L. Smith. 1995. Ecological units of the eastern United States - first approximation (map and booklet of map unit tables). Presentation scale 1:3,500,000, colored. USDA Forest Service, Atlanta, GA.

Cleland, D. T., J. A. Freeouf, J. E. Keys, Jr., G. J. Nowacki, C. Carpenter, and W. H. McNab. 2007. Ecological subregions: Sections and subsections for the conterminous United States. A. M. Sloan, cartographer. General Technical Report WO-76. USDA Forest Service, Washington, DC. [1:3,500,000] [CD-ROM].

MRLC - NLCD Map Zones

The Multi-Resolution Land Characteristics (MRLC) Consortium is a group of federal agencies who first joined together in 1993 to purchase Landsat 5 imagery for the conterminous U.S. and to develop a land cover dataset called the National Land Cover Dataset. In 1999, a second-generation MRLC consortium was formed to purchase three dates of Landsat 7 imagery for the entire United States (MRLC 2001) and to coordinate the production of a comprehensive land cover database for the nation called the National Land Cover Database (NLCD 2001). “Mapping zones” were developed for use by consortium members and any other partners, as described by Homer et al. (No date).

Under contract to the Interagency LANDFIRE project, NatureServe ecology staff have attributed Ecological Systems to MRLC Map Zones in the coterminous western U.S. from New Mexico north to Montana and west. These distributional data are being continually revised as review comments are provided to NatureServe by LANDFIRE partners and other partners. For the eastern U.S., ecological systems will be attributed to map zones during the remainder of 2006 and 2007.

Ecological Divisions

Ecological Divisions are sub-continental landscapes reflecting both climate and biogeographic history. Continent-scaled climatic variation, reflecting variable humidity and seasonality (e.g. Mediterranean vs. dry continental vs. humid oceanic) are reflected in these units, as are broad patterns in phytogeography (e.g. Takhtajan 1986. The division lines were modified by using ecoregions established by The Nature Conservancy and World Wildlife Fund throughout the Western Hemisphere. All ecological systems are attributed to one or more ecological divisions, and the names of the systems include the divisional ‘center of distribution’ as detailed in Comer et al. (2003).

Takhtajan, A. 1986. Floristic Regions of the World. Transl. by T.J. Crovello and ed. by A. Cronquist. University of California Press, Berkeley.

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US ESA and Canada COSEWIC national statuses. The Heritage Conservation Status Rank system and definitions. Sources for names of plant, animal, and ecological community records in <i>NatureServe Explorer</i>