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Out of sight and out of mind? The conservation status of subterranean biodiversity in the United States and Canada

Published Article

United States, Canada, Texas

Publication date: June 5, 2025

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Subterranean ecosystems host globally significant but highly imperiled biodiversity, yet conservation assessments rarely capture their status. Reviewing 1,460 cave‑obligate species in the United States and Canada, this study compares NatureServe, IUCN Red List and federal/state listings. Only 9.3% of species have IUCN assessments, and just 41 are listed or proposed under the U.S. Endangered Species Act. Vertebrates and decapods are overrepresented in assessments, while arachnids, millipedes and insects remain largely unassessed. Most federally listed and IUCN‑assessed species occur in Texas’ Edwards Plateau and Balcones Escarpment karst regions. Major threats include habitat degradation, pollution, recreation, climate change and groundwater extraction, though threat data are missing for many taxa. The findings underscore substantial knowledge gaps and offer recommendations to strengthen conservation assessments and policies for subterranean biodiversity.

Subject Tags

  • Biodiversity
  • Groundwater

Abstract

Subterranean ecosystems harbor globally important yet highly threatened biodiversity. Unfortunately, subterranean biodiversity is often neglected in regional and global conservation initiatives, including conservation assessments. We reviewed the conservation status and threats to subterranean species based on the two most popular conservation assessment protocols in North America, NatureServe and International Union for Conservation of Nature (IUCN) Red List, as well as federal and state/provincial protection status of the 1,460 described cave-obligate species occurring in the United States and Canada. Only 9.3% of species have been assessed under IUCN Red List criteria compared to 77.9% of species assessed under NatureServe criteria; notably, 1,065 and 116 of species are assessed at an elevated risk of extinction by NatureServe and IUCN Red List, respectively. Just 41 species are listed or proposed to be listed under the U.S. Endangered Species Act and none of the 10 species that occur in Canada are federally listed. Vertebrates (fishes and salamanders), decapods (crayfishes and shrimps), and U.S. federally listed species are overrepresented on the list of species with IUCN Red List assessments compared to other taxonomic groups, particularly arachnids, millipedes, and insects. Most species assessed under IUCN Red List criteria as well as federally listed species occur in the Edwards Plateau and Balcones Escarpment karst region of Texas. Major threats frequently reported in conservation assessments include habitat degradation, pollution/contamination, recreational activities, climate change, and groundwater exploitation; however, information on threats was lacking for most species for nearly all major taxonomic groups, except decapods, fishes and salamanders. The intrinsic vulnerability of subterranean biodiversity coupled with the many potential threats facing species and extensive biodiversity knowledge gaps makes assessing their conservation status and ultimately their protection a challenging endeavor. We highlight several limitations of implementing current conservation assessment approaches while offering recommendations to improve our ability to assess the conservation status of subterranean biodiversity to better inform sound local to global conservation policies and actions.

Citation

Niemiller, M. L., Zigler, K. S., Curtis, A. N., Trapeni, C. M., Slay, M. E., Culver, D. C., ... & Kendall Niemiller, K. D. (2025). Out of sight and out of mind? The conservation status of subterranean biodiversity in the United States and Canada. Biodiversity and Conservation, 34(8), 2851-2882. https://doi.org/10.1007/s10531-025-03099-6

TNC Authors

  • Michael E. Slay
    Ozark Karst Program Manager, Arkansas
    The Nature Conservancy
    Email: mslay@tnc.org