WHY IS HABITAT IMPORTANT? THE FIGHT TO KEEP PROTECTION IN THE ENDANGERED SPECIES ACT

by Brenda McComb, PhD

That seems like a silly question, right? Of course we need habitat to sustain species. But the answer is important to understand to appreciate the effects of an impending change to the Endangered Species Act. The federal government is now proposing to eliminate habitat as a cause for jeopardizing a species’ extinction. Let’s take a closer look at what habitat is and how an understanding of habitat relates to these proposed changes to federal policy.

What is habitat?

People often say, “Habitat is the place where a species lives”, but we can find individuals of some species living in very odd places that we would not consider habitat for that species. For instance, young spotted owls occasionally disperse into suburban areas where they would be unlikely to persist. Hence, we need to be more specific—habitat includes those resources necessary to support both individuals and populations. These resources are food, cover to provide protection from weather and predation, and the space over which these specific food and cover resources are available in sufficient supply to support individuals and populations. Each species and each population have their own habitat requirements (Krausman 1999). References to “wildlife habitat” are meaningless unless a particular wildlife species is identified because everything is habitat for something (Krausman 1999, Hall et al. 1997, Garshelis 2000, McComb 2016). We prefer to define “habitat” as the set of resources necessary to support a population over space and through time (McComb 2016). The ultimate function of habitat is to ensure survival of individuals, and more importantly of populations.

How is habitat federally protected?

When a species is listed as threatened or endangered, the government includes habitat within its scope of protection.

The ESA prohibits the “taking” of endangered species where "take" is defined as “to harass, harm, pursue, hunt, shoot, wound, kill, trap, capture, or collect, or to attempt to engage in any such conduct.” For the last 50+ years, the government has recognized the importance of protecting listed species from both direct harmful actions (killing or injuring) AND from indirect harmful actions, such as loss of habitat, or habitat modification that may lead to injury or death or reduce population viability.

The U.S. Fish and Wildlife Service (USFWS) and the National Marine Fisheries Service (NMFS) are proposing to rescind the regulatory definition of "harm" and rely solely on the statutory definition of "take." This proposed change would narrow the scope of "take" to exclude some forms of habitat modification that indirectly impact species. But defining habitat as critical for species persistence and recovery has been a key component of ESA policy. For those species listed under the Endangered Species Act (ESA) as threatened or endangered, the federal government will designate “critical habitat” for any listed species (FWS 2017). Once designated, any alteration of critical habitat that imperils one or more individuals of any protected species constitutes a violation of the law (Sagoff 1997), unless the nonfederal landowner has an incidental “take” permit (ITP) (Smallwood 2000). If a federal agency concludes that a Habitat Conservation Plan developed by the landowner will result in no net population decline then the agency can issue an incidental take permit, that allows the landowner to continue to manage the land without violating the law even though some individuals of the protected species are harmed. To date, without an ITP, alteration of habitat would constitute harm to a species, and this has been a powerful tool for habitat protection and species recovery. Indeed, many listed species have been listed based on loss of habitat (Eichenwald et al. 2020). Habitat protection and recovery have been key to recovery for species such as the redcockaded woodpecker of the southern pine forests, whose status was changed from endangered to threatened.

Should habitat be removed from federal protection?

The USFWS and NMFS are proposing to rescind the regulatory definition of “harm” in the Endangered Species Act regulations (USDI 2025 a, b). They state that the existing regulatory definition of “harm,” which includes habitat modification, runs contrary to the best meaning of the statutory term “take.” (USDI 2025a,b). Currently harm may include “significant habitat modification or degradation where it actually kills or injures wildlife by significantly impairing essential behavioral patterns, including breeding, feeding or sheltering.” (USDI 2025b). The agencies contend that “harm” in the definition of `take' in the Act means an act which actually kills or injures wildlife but not habitat. The agencies propose to rescind the current regulatory definition of “harm” (i.e., habitat modification). Such a change would mean that if a landowner were to cut down a nest tree for an endangered bird, and that nest had young in it, then ESA would be violated (direct harm to individuals of the species). But if the nest tree were no longer being used, or if a potential nest tree that could be used in the future was not being used now, then that nest tree could be cut down without legal “harm” to individuals of that species. While this revision would not affect ITPs that have been granted as of the date this new regulation becomes final, the implications for land managers and for biologists responsible for sustaining populations or recovering populations is obvious in that habitat important to sustaining the species can be lost over time.

Is this policy change logical?

If we accept that habitat provides the resources for an individual to survive or a population to sustain itself, as it would appear the federal agencies do when describing “critical habitat” (FWS 2017), then not considering habitat loss or degradation as ‘harm’ and a form of ‘take’ is illogical, resulting in a law that has lost its connection with reality. What happens to individuals which do not receive an adequate quantity or quality of food? Or protection from cold or heat (likely more important in a warming future with climate change), or a means of escaping predators or competitors? What would happen to those individuals is the same as would happen to you or me: we would be under several forms of stress and eventually with continued lack of access to resources, we would die. Similarly, if we wish populations to be self-sustaining, then the resources must be available over areas large enough to provide those resources for multiple generations of a population. Quite simply, habitat for a species is a part of its inherent biology and ability to exist and is clearly a part of any recovery plan to rebuild populations that are listed under ESA. To ignore loss of habitat as a component of ‘harm’ or ‘take’ would ignore the thousands of scientific studies that have related habitat quantity and quality to species occurrence, distribution and sustainability. It is both illogical and inconsistent with our state of knowledge about animal habitat relationships and will very likely contribute to continued declines of some species listed under ESA.

Acknowledgements and a Disclaimer

I thank Drs. Candace Bonner, Dianna Fisher, Sharon Selvaggio, and Joan Hagar for their helpful comments on this article. Be aware that while I was asked to write this piece as someone who has studied animal habitat relationships for over 45 years, I do not have a background in law, so I recognize that my interpretation of the ESA may be inadequate.

References

■ USDI (Department of the Interior, Fish and Wildlife Service, and Department of Commerce, National Oceanic and Atmospheric Administration). 2025a. Proposed Rule: Rescinding the Definition of “Harm” Under the Endangered Species Act. Federal Register 90 (73): 1610216105. https://www.federalregister.gov/ documents/2025/04/17/2025-06746/ rescinding-the-definition-of-harm-under-theendangered-species-act

■ USDI (Department of the Interior, Fish and Wildlife Service. 2025b. Part 17 -- Endangered and Threatened Wildlife and Plants, Subpart A —Introduction and General Provisions, 17.3 Definitions). https://www.ecfr.gov/current/ title-50/chapter-I/subchapter-B/part-17/ subpart-A/section-17.3

■ Eichenwald, A.J., M.J Evans, J.W. Malcom. 2020. US imperiled species are most vulnerable

to habitat loss on private lands. Frontiers in Ecology and the Environment 18 (8): 439-446. https://doi.org/10.1002/fee.2177

■ FWS (U.S. Fish and Wildlife Service) 2017. Critical habitat. What is it? U. S. Fish and Wildlife Service, Endangered Species Program. Falls Church, VA. https://www.fws.gov/sites/ default/files/documents/critical-habitat-factsheet.pdf

■ Garshelis, D.L. 2000. Delusions in habitat evaluation: Measuring use, selection, and importance. Pages 111–164 in L. Boitani and T.K. Fuller (eds.). Research Techniques in Animal Ecology: Controversies and Consequences. Columbia University Press, New York.

■ Hall, L.S., P.R. Krausman, and M.L. Morrison. 1997. The habitat concept and a plea for standard terminology. Wildlife Society Bulletin 25:173–182.

■ Krausman, P.R. 1999. Some basic principles of habitat use. In K. L. Launchbaugh, K.

D. Sanders, and J.C. Mosley (eds.). Grazing Behavior of Livestock and Wildlife. Idaho Forest, Wildlife and Range Exp. Sta. Bull No. 70. University of Idaho, Moscow, pp. 85–90.

■ McComb, B. C. 2016. Wildlife habitat management: concepts and applications in forestry. 2nd ed. CRC Press, available as open source: https://open.oregonstate.education/ wildlifehabitat/

■ NOAA Fisheries. 2022. Glossary: Endangered Species Act. USDI NOAA https://www. fisheries.noaa.gov/laws-and-policies/glossaryendangered-species-act

■ Sagoff, M. 1997. Muddle or muddle through?: Takings jurisprudence meets the Endangered Species Act. William and Mary Law Review 38:825–993.

■ Smallwood, K.S. 2000. A crosswalk from the Endangered Species Act to the HCP Handbook and real HCPs. Environmental Management 26(1):23–35.