Quantify endangered species listings

![Figure][1] The snowy egret was removed from Florida's protected species list after the state adopted a quantitative listing system. PHOTO: CMCNEILL17/ISTOCKPHOTO The U.S. Congress is considering changes to the Endangered Species Act (ESA) of 1973, a law that protects more than 1500 U.S. species facing extinction. Currently, decisions about which species should be protected appear arbitrary and are frequently litigated ([ 1 ][2]). The ESA could benefit from a transparent and predictable quantitative framework that standardizes these decisions. However, such improvements do not require any changes to the Act itself, and Congress's proposed revisions would have the opposite effect, making classification decisions more political and unpredictable. Countries such as Canada ([ 2 ][3]) and New Zealand ([ 3 ][4]) already use quantitative thresholds to determine species' extinction risk ([ 4 ][5]). Using such systems as a model, Florida adopted a quantitative listing system in 2010 that led to protection for 40 species and removal of protection for 15 that do not merit it ([ 5 ][6]). The quantitative system uniformly applies objective criteria such as current population size and rate of decline to all species. Instituting quantitative definitions for “threatened” and “endangered” does not require any legislative change to the ESA. The law already gives agencies authority to develop a listing system by regulation. Such regulations should require listing decisions to be made according to criteria similar to those that have been developed by scientists and extensively tested ([ 4 ][5]). This strategy would be substantially more effective in meeting the ESA's goals than the proposals under discussion in Congress, which include giving state governors veto power over decisions about the species in their state ([ 6 ][7]). Our understanding of extinction risk has advanced since 1982 when listing categories under the ESA were last amended. Defining these terms, and making decisions about listing and recovery more quantitative and legally defensible, would reduce controversy and free up resources to recover wildlife. 1. [↵][8]1. A. Treves, 2. J. T. Bruskotter , BioScience 61, 584 (2011). [OpenUrl][9][FREE Full Text][10] 2. [↵][11]1. R. S. Waples et al ., BioScience 63, 723 (2013). [OpenUrl][12][Abstract/FREE Full Text][13] 3. [↵][14]1. A. J. Townsend et al ., New Zealand threat classification system manual (New Zealand Department of Conservation, 2007); [www.doc.govt.nz/Documents/science-and-technical/sap244.pdf][15]. 4. [↵][16]International Union for Conservation of Nature (IUCN), IUCN Red List categories and criteria: Version 3.1 (IUCN Species Survival Commission, 2001). 5. [↵][17]Florida Fish and Wildlife Conservation Commission, Biological status review (2010); . 6. [↵][18]U.S. Senate, Endangered Species Management Self-Determination Act, Senate bill S. 935 (2017); [www.congress.gov/bill/115th-congress/senate-bill/935][19]. [1]: pending:yes [2]: #ref-1 [3]: #ref-2 [4]: #ref-3 [5]: #ref-4 [6]: #ref-5 [7]: #ref-6 [8]: #xref-ref-1-1 "View reference 1 in text" [9]: {openurl}?query=rft.jtitle%253DBioScience%26rft_id%253Dinfo%253Adoi%252F10.1525%252Fbio.2011.61.8.2%26rft.genre%253Darticle%26rft_val_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Ajournal%26ctx_ver%253DZ39.88-2004%26url_ver%253DZ39.88-2004%26url_ctx_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Actx [10]: /lookup/ijlink/YTozOntzOjQ6InBhdGgiO3M6MTQ6Ii9sb29rdXAvaWpsaW5rIjtzOjU6InF1ZXJ5IjthOjQ6e3M6ODoibGlua1R5cGUiO3M6NDoiRlVMTCI7czoxMToiam91cm5hbENvZGUiO3M6MTA6ImJpb3NjaWVuY2UiO3M6NToicmVzaWQiO3M6ODoiNjEvOC81ODQiO3M6NDoiYXRvbSI7czoyNToiL3NjaS8zNTYvNjM0NS8xMzQyLjEuYXRvbSI7fXM6ODoiZnJhZ21lbnQiO3M6MDoiIjt9 [11]: #xref-ref-2-1 "View reference 2 in text" [12]: {openurl}?query=rft.jtitle%253DBioScience%26rft_id%253Dinfo%253Adoi%252F10.1093%252Fbioscience%252F63.9.723%26rft.genre%253Darticle%26rft_val_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Ajournal%26ctx_ver%253DZ39.88-2004%26url_ver%253DZ39.88-2004%26url_ctx_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Actx [13]: /lookup/ijlink/YTozOntzOjQ6InBhdGgiO3M6MTQ6Ii9sb29rdXAvaWpsaW5rIjtzOjU6InF1ZXJ5IjthOjQ6e3M6ODoibGlua1R5cGUiO3M6NDoiQUJTVCI7czoxMToiam91cm5hbENvZGUiO3M6MTA6ImJpb3NjaWVuY2UiO3M6NToicmVzaWQiO3M6ODoiNjMvOS83MjMiO3M6NDoiYXRvbSI7czoyNToiL3NjaS8zNTYvNjM0NS8xMzQyLjEuYXRvbSI7fXM6ODoiZnJhZ21lbnQiO3M6MDoiIjt9 [14]: #xref-ref-3-1 "View reference 3 in text" [15]: http://www.doc.govt.nz/Documents/science-and-technical/sap244.pdf [16]: #xref-ref-4-1 "View reference 4 in text" [17]: #xref-ref-5-1 "View reference 5 in text" [18]: #xref-ref-6-1 "View reference 6 in text" [19]: http://www.congress.gov/bill/115th-congress/senate-bill/935