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Predicting concentrations of at-risk species nationally

February, 2015

Geographic distribution of species formally listed as threatened and endangered, and imperiled according to NatureServe conservation ranks.
Geographic distribution of species formally listed as threatened and endangered, and imperiled according to NatureServe conservation ranks.
In the last decade there has been growing use of ecosystem services to economically justify biodiversity conservation programs that ultimately contribute to human well-being. Notwithstanding the substantial benefits attributed to biotic resources, the short term costs of biodiversity degradation remain overshadowed by the short term economic benefits of resource extraction and land use intensification to support growing human populations. For this reason, recent efforts to conserve biodiversity are largely insufficient to offset human drivers (habitat loss, overexploitation, and invasive exotic species) of increased species rarity and extinction. Thus, global biodiversity has not only continued to decline, but is declining at an accelerated pace. To anticipate where future concentrations of at-risk species are likely to emerge, the scientists participating in this study will develop empirical models that help conservation practitioners understand drivers of species rarity.


The researchers will create a georeferenced database that will contain the following:

  • Response variables – the count of species formally listed as threatened or endangered (under the U.S. Endangered Species Act); the count of species considered to be imperiled (NatureServe conservation ranks G1 and G2) with extinction. 
  • Candidate predictors – annual climate regime variables, seasonal climate regime variables, mean elevation, elevation range, proportion protected lands by class, proportion intensive land uses, human population, proportion of the land base under extractive resource use (timber harvesting, mining), and a set of regional context variables that attempt to quantify the degree of human impact within some ecologically relevant neighborhood.

These data will be used to develop a priori competing models based on endemism and refuge hypotheses. The endemism hypothesis is expected to dominate in environmentally harsh and physiographically diverse systems that are known to support a disproportionately high number of narrowly distributed (i.e., endemic) species. The refuge hypothesis is expected to dominate in systems where human impacts are high except in a few areas (i.e., refugia) that have escaped development owing to land ownership patterns or remoteness to centers of human settlement.

Key Findings

Using contemporary species occurrence records obtained from NatureServe and its network of natural heritage programs, we found hotspots of species’ listing in Hawaii, in the southern Appalachian Mountains, in peninsular Florida, in coastal parts of the Southeast and eastern Gulf States, in California Mediterranean-climate regions, and in the Cascade and lowland mixed forests of the Pacific Northwest. This is not a new finding – since the late 1990s, scientists have consistently recognized these hotspots, despite variation in analytical methods and a substantial increase in the number of listed species. However, we have also identified a new, emerging area of listed-species concentration associated with the interior highlands and plateau region of southern Missouri, northern Arkansas, western Kentucky, and southern Illinois and Indiana. Many regions outside of these hotspots contain very few listed species.  Overall, 54 percent of the U.S. land area has no listed species in NatureServe’s databases.


The geographic occurrence of listed and imperiled species across the U.S. is clearly nonrandom, with available data showing that species of conservation concern concentrate in distinct regions of the country (see associated image). Although the conservation implications of these endangerment hotspots has been discussed in the past, conservation science has struggled with how to use this information to move beyond the species-by-species conservation strategies that have thus far dominated conservation efforts. One approach that has recently been formalized in the USDA, Forest Service planning rule governing biodiversity conservation on lands it administers is based on the notion of coarse-filter conservation strategies.  In general, coarse filters are based on attributes that can be measured easily and inexpensively, relying on existing inventories (e.g., remotely sensed imagery, weather station data), and describing broad characteristics of the environment. As such, coarse filters are but another kind of surrogate that attempts to identify the environmental cues – the amounts and spatial distribution of bio-physical factors – that, in the case of this study, predict where we expect at-risk species to concentrate. This study will develop spatially explicit models of at-risk species occurrence in an effort to anticipate how climate and land use change may affect the geographic pattern of at-risk species over time.



Threatened and endangered species geography.  Ignite Session: The Endangered Species Act Turns 40:  Lessons learned for conservation of threatened and endangered species in the United States. Ecological Society of America Annual Meeting. 4-9 August 2013.  Minneapolis, MN.

Issues in Ecology Workshop.  Baltimore, MD.  15-17 Jan 2014.  Presented material on the geography of listed and at-risk species.  Reviewed multi-species Habitat Conservation Planning and their coincidence with listed and at-risk species hotspots.  Invited participant.  Ecological Society of America Sponsored.

Why biodiversity matters to the USDA Forest Service.  AAAS Science and Technology Policy Fellowship and the AAAS Fellows Biodiversity Affinity Group.  29 April 2014.  Washington, DC.

Papers in review or in press:

Evans, D. M., J. P. Che-Castaldo, D. Crouse, F. W. Davis, R. Epanchin-Niell, C. H. Flather, R. K. Frohlich, D. D. Goble, Y. Li, T. D. Male, L. L. Master, M. Moskwik, M. C. Neel, B. R. Noon, C. Parmesan, M. W. Schwartz, J. M. Scott, B. K. Williams.  in review.  Species recovery in the United States: assessing the Endangered Species Act.  Issues in Ecology #00.  000 p.

U.S. Department of Agriculture, Forest Service. in press.  Interim update of the 2010 Renewable Resource Planning Act assessment.  Gen. Tech. Rep. WO-000.  Washington, DC.  000 p.

Principal Investigators:
Philip A. Stephens - Durham University - United Kingdom

Research Staff:
Funding Contributors:
US Forest Service Research and Development - RPA Assessment research program