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Contacts: Noah Greenwald


The Endangered Species Act works, but how? The procedures behind listing and protecting species can be complicated, but it’s helpful for anyone interested in conservation to understand the law’s ins and outs. Listing is essential, because only after species are listed do they receive the critical benefit of the Act’s substantial protections.

To date, 2,244 species are listed as threatened or endangered under the Endangered Species Act, with 1,618 of those in the United States. Of the listed species in the United States, 884 are plants; 307 are invertebrates, including insects, mollusks, and others; 163 are fishes; 95 are birds; 96 are mammals; 36 are reptiles;  35 are amphibians; and two are fungi — lichens, actually. For both plants and animals, many more species are listed as endangered than as threatened.

Petitions and lawsuits by the Center have so far resulted in the listing of more than 700 plants and animals — and we've helped save hundreds more in ways other than listing. We aim to help protect and list many others.


The Act is implemented by two federal agencies, the U.S. Fish and Wildlife Service, under the auspices of the Interior Department — responsible for protecting land animals, plants, and freshwater fish — and the National Marine Fisheries Service, within the National Oceanic and Atmospheric Administration — responsible for protecting marine species.

Species can be nominated for listing in one of two ways. The Fish and Wildlife Service and National Marine Fisheries Service can, of their own accord, single out a species for listing. Much more commonly, however, one of the agencies will be spurred by a citizen petition by a group or individual to list a given plant or animal.

Once a petition is received, the agency has 90 days to make a “finding” on the document declaring whether or not it contains substantial information showing that federal protection for the species “may be warranted.” If the finding is positive, the agency then has one year to conduct a status review of the species — that is, an assessment of its plight, population trend, and threats. At the one-year mark, the agency must make another finding that the listing either is or isn’t warranted. If protection isn’t found warranted, the listing process goes no further — unless and until a concerned party takes legal action against the agency.

If listing is found to be warranted, the agency can go one of two routes, either declaring listing “warranted but precluded” or issuing an official proposal to list the species. In the former case, the species’ protection is put on the shelf, supposedly in favor of higher-priority listings, and the species waits on the “candidate list” in some cases for years. In the case of a listing proposal, the Fish and Wildlife Service or Fisheries Service has one year to publish its final decision on listing, and if listing is ultimately greenlit, protections for the species must officially take effect 30 days after the decision is made. All agency findings and rules are published in a Department of the Interior publication called the Federal Register.

Under these legally binding timelines, the listing of a species should take at most two years from the submission of a petition. But despite the obvious urgency to protect species as quickly as possible, this has rarely occurred. Instead, species have experienced delays in listing in many cases lasting decades, and the majority have only been listed following litigation by the Center for Biological Diversity and other organizations. Of currently listed species in the United States covered by the U.S. Fish and Wildlife Service, 41 percent were listed only after a lawsuit was filed, 39 percent after a petition was filed, and only 20 percent solely on the agency’s own initiative.

The listing of species slowed to a crawl during the eight years of the Bush administration, which listed a mere 62 species, all under court order, for a rate of seven species per year. In contrast, the Clinton administration listed 522 species for a rate of 65 species per year and the Bush Sr. administration listed 231 species for a rate of 57 species per year. Meanwhile, literally hundreds, if not even thousands, of species await protection.


Once either the Fish and Wildlife Service or the Fisheries Service has granted an at-risk species the status of “threatened” or the more serious status of “endangered,” that agency is required to designate for the species federally protected habitat, or critical habitat, which limits activities that harm species’ habitat. The agency is also required to develop a recovery plan for the species to act as a road map to recuperation.

If any citizen or public-interest group feels that a federal agency is not protecting a listed species as the Act requires, that party may file a lawsuit against the agency.

Photo © Gerald and Buff Corsi/California Academy of Sciences