Jump to main content or area navigation.

Contact Us

Water: Wetlands Program Development Grants

NatureServe: Wetland Program Development Grants (WPDGs) Case Studies

Helping state and tribal programs assign biodiversity value to geographically isolated wetlands


NatureServe is a non-profit organization working to provide scientific information and tools to help guide effective conservation actions. NatureServe works through a network of international natural heritage programs to provide information on species and ecosystems of special concern. Government agencies, states, tribes, conservation groups, landowners and resource managers can then make informed decisions about how to effectively protect these valuable resources.

NatureServe and its partners have made significant advancements in a number of endeavors enabling good resource management including: the development of a classification approach for ecological systems which provide an integrated framework that is readily applicable to mapping efforts, resource assessment, monitoring and management; establishment of a system to asses and rank the conservation status (critically imperiled, G1 ? secure, G5) of biodiversity elements (i.e. plants, animals and ecological communities) in terms of their global status; and management of the NatureServe Explorer website which houses searchable data on over 60,000 plants, animals, vegetative associations and ecological systems. States and tribes can, and no doubt will, use many of the above resources in developing the various components of their comprehensive wetland programs.

WPDG Activity

The issue of wetland jurisdiction continues to be an area of concern as court cases are brought to the U.S. Supreme Court. The court decision in the case involving the Solid Waste Agency of Northern Cook County vs. U.S. Army Corps of Engineers in 2001 and the more recent cases of Rapanos v. United States and Carabell v. U.S. Army Corps of Engineers (2006) all raised issues over the extent of federal jurisdiction over geographically isolated wetlands. The misunderstandings among scientists, resource managers and policy makers are amplified by the lack of a common definition for 'isolated wetland' in the legal arena. An overall lack of baseline data describing the status and trends of most wetland resources makes it difficult to systematically assign values to those wetland resources which are isolated. NatureServe received a Wetland Program Development Grant (WPDG) in 2003 to examine the biodiversity value of wetlands geographically isolated from navigable waters. At-risk species and communities supported by these wetland types were used as the gauge for determining the biodiversity value.

NatureServe worked with State Natural Heritage programs to evaluate geographically isolated wetland systems and associated species. The study used a nationally standardized classification system for wetland types that was based on the United States National Vegetation Classification (US-NVC) system. Geographically isolated wetlands (in the context of this study) represented 81 of the 276 wetland types described. The majority (77%) of the geographically isolated wetlands identified were in the "depressional" hydrogeomorphic class, while the remaining wetlands were fairly equally divided between "extensive wet flat" and "seepage-fed sloping". NatureServe linked "at-risk" biodiversity elements (plants, animals and vegetative associations) to isolated wetlands. The "at-risk" status of species in this study was based on NatureServe's central database which links biodiversity elements to a conservation status. Species considered "at risk" had a conservation status rank of G1 (critically impaired), G2 (imperiled) or G3 (vulnerable). The following table highlights some of their major findings.

Number of At-Risk Plant and Animal Species in Isolated Wetlands, by Geographic Region
This table was adapted from data in "Biodiversity Values of Geographically Isolated Wetlands in the U.S.", published by NatureServe in 2005.

Geographic Region At-Risk Species Dependence on Isolated Wetlands Total Number of At-Risk Species in Region
Obligate Facultative Unconfirmed*
North Atlantic Coast 2 10 1 13
Central Atlantic Coast 7 12 2 21
South Atlantic and Gulf Coast 25 38 13 76
Upper Great Lakes 1 7 2 10
Central Hardwoods and Interior Highlands 4 11 6 21
Great Plains and Tallgrass Prairie 1 3 2 6
Intermountain and Rocky Mountain 16 19 3 38
Southwest 7 7 5 19
Pacific Coast 45 81 1 127
Alaska 0 1 0 1
Hawai'i 6 22 7 35
U.S. Total# 95 153 26 274

* When a species was known to occur in wetland habitats according to the project definition for isolated wetlands but not established to have a specific link to a classified wetland type, it was listed as "unconfirmed".
# Since species could occur in more than one region, total counts for the U.S. do not equal the sum of values across regions.

In addition to the data provided above, there were a total of 270 at-risk vegetation associations documented as characteristic of geographically isolated wetlands and 67% do not occur in any of other habitat. Results of this study will help states, tribes, local governments, landowners, developers and others associated with wetland management appreciate the biodiversity value of isolated wetlands, where so much uncertainty exists as to their future protection under the Clean Water Act. The 274 at-risk species depending on these habitats support increasing evidence on the ecological importance of geographically isolated wetlands.

The final report entitled "Biodiversity Values of Geographically Isolated Wetlands in the United States" was released in December 2005 and has thus far been well received. A targeted e-mail of the report's availability was sent out and in the 9 days following its release, 1184 (~ 70%) of 1700 email recipients stayed an average of 7 minutes on the NatureServe webpage containing the report's Executive Summary.

Current Work and Future Plans

State Natural Heritage Program biologists throughout the United States continue to inventory isolated wetlands and their associated at risk species and plant associations on a project by project basis. NatureServe continues to seek additional funding to conduct the inventory and mapping needed to fill critical knowledge gaps identified in the study. In addition, NatureServe is working to develop mitigation performance standards for all wetland types (not just isolated wetlands) based on ecological integrity measures of reference sites.

For more information, please visit the NatureServe Web site (http://www.natureserve.org/)  Exit EPA Disclaimer

Jump to main content.