Criteria: Imperiled Species
Data Source: NatureServe
Last Updated: August 2019
WHY IS THIS CRITERION IMPORTANT?
Species are important because of their role within an ecosystem. The term ecosystem describes the complex web of interactions between the living community (plants and animal species) and the non-living community (soil, air, water, light). Changes in the composition of species within that community (i.e. biodiversity: the number of species and their relative abundance) can thus, have a major influence on the system as a whole. The loss of a keystone species (a species upon which an ecosystem heavily depends; e.g. red-cockaded woodpecker, longleaf pine, grey wolf, beaver, etc.) may result in a regime shift in which the ecosystem has been fundamentally changed (i.e. ecosystem loss).
For a species to be categorized as imperiled or critically imperiled, they must be at high or very high risk of extinction, respectively. Conservation and forest management work that restores, protects and/or improves habitat for at-risk species is critical because (1) it can be difficult to predict how ecosystems will respond to a species (or biodiversity) loss, and (2) these practices help improves the systems’ resiliency (i.e. ability to withstand and recover from stressors and disturbances) into the future.1
This criterion helps our members understand where imperiled species are present.
SUMMARY
This criterion estimates the number of critically imperiled or imperiled species present in the geography of interest. In the Assessment Area Dashboard we use NatureServe data to report the following information at a Hex and Assessment Area level:
- Total number of imperiled species (within NatureServe G1/G2, T1/T2 and ESA E/T)
- Percentage of imperiled species in the selected geography that are forested vs. non-forested
- Percentage of forested imperiled species in the selected geography that are upland vs. wetland
- Percentage of forested imperiled species in the selected geography that are NatureServe (G1/G2) rank, ESA (E/T) listed or cross-listed (both)
In doing so, Forests in Focus members can identify areas of high significance to at-risk species that potentially overlap with their sourcing areas.
| Ranking | Critically Imperiled | Imperiled | Endangered | Threatened |
| Type | NatureServe Global Rank (1-5): | NatureServe Global Rank (1-5): | Endangered Species Act (ESA): | Endangered Species Act (ESA): |
| Definition | At very high risk of extinction or elimination due to very restricted range, very few populations or occurrences, very steep declines, very severe threats, or other factors.2 | At high risk of extinction or elimination due to restricted range, few populations or occurrences, steep declines, severe threats, or other factors.3 | Any species which is in danger of extinction throughout all or a significant portion of its range.4 | Any species which is likely to become an endangered species within the foreseeable future throughout all or a significant portion of its range.5 |
| Symbol | Species: G1
Subspecies: T1 |
Species: G2
Subspecies: T2 |
ESA: E | ESA: T |
RISK THRESHOLDS
| CRITERIA | LOWER RISK | MEDIUM RISK | HIGHER RISK |
| Imperiled Species | No known imperiled or critically imperiled species present. | Count of imperiled or critically imperiled species that is less than or equal to the national median (2 in a Hexagon or 27 in an Assessment Area). | Count of imperiled or critically imperiled species that is greater than the national median (2 in a Hexagon or 27 in an Assessment Area). |
TECHNICAL INFORMATION
NatureServe is a non-profit organization with a network of over 80 member programs that collect and maintain a unique body of data on the location, condition, and status of plants, animals, and ecosystems. To learn more about NatureServe, visit their website: https://www.natureserve.org/
NatureServe assigns global conservation status ranks to species (or ecosystems). They do so by scoring species on ten conservation status factors, then weight and aggregate these scores to produce a total. Species status ranks range from Critically Imperiled (G1) to Imperiled (G2), Vulnerable (G3), Apparently Secure (G4) and Secure (G5).6
NatureServe leveraged their robust dataset, managed with their ‘Biotics’ database, to provide data for the Imperiled Species criterion. This database includes information on location, conservation status, habitat associations, threats, and high conservation value (HCV) metrics that are available at a national level. To create this database, NatureServe aggregated and reconciled data from natural heritage program field inventories in each state. Which allowed them to (1) access current information on imperiled species and legally protected locations across the United States, and 2) combine datasets to fully assess the global imperilment of species and subspecies.
POSSIBLE DATA AND ANALYSIS LIMITATIONS
For the Imperiled Species criteria, the location of globally imperiled species (G1 – G2), globally imperiled subspecies (T1- T2) and the U.S. Endangered Species Act (ESA) endangered (E) or threatened (T) species were included, totaling 5,062 taxa from 45 of the lower 48 states (excluding all species from Massachusetts, Pennsylvania, and Rhode Island, and only plant species from Washington) and adjacent Canadian provinces. The Imperiled Species criterion essentially counts the presence of an imperiled species in the geography of interest. As a safeguard against old records from old sources (e.g., museum specimens never reconfirmed) being used, NatureServe only included species that have been documented at a location within the last 42 years (i.e., since 1978).
The methodology we utilize is designed to support an understanding of the nation’s forest resource and to support observations about trends at different scales. As with any analysis, there are statistical limitations to results, especially at finer scales. The biodiversity criterion does not display imperiled species information for Massachusetts, Pennsylvania, and Rhode Island or for imperiled plant species located in Washington state.
1 U.S. Fish & Wildlife Service. Why Save Endangered Species? 2005.
2, 3, 6 NatureServe. Definitions of NatureServe Conservation Status Ranks. Website.
4, 5 NOAA Fisheries. Endangered Species Act. Website.