Chronic Underfunding and Delays in Protecting Species Hinder the Endangered Species Act

Written by
Columbia Climate School and Keely Swan, Princeton School of Public and International Affairs
Oct. 12, 2022

Most species are not receiving protection until their populations are precariously small, and funding available for their protection has been insufficient, thus dimming prospects of species’ recovery.

Since its passage in 1973, the U.S. Endangered Species Act (ESA) has been the strongest law to prevent species extinctions in the United States, and has served as a model of conservation policy to other nations. However, the law has resulted in relatively few successes in helping species recover. Out of more than one thousand species that have been listed by the ESA in the past 48 years, only 54 have recovered to the point where they no longer need protection.

A new study, published in the journal PLOS ONE, examines why so few species have recovered successfully. Researchers from Princeton University and Columbia University find that the combination of delayed protection for imperiled species, small population sizes at the time of listing, and insufficient funding continue to hamper the ESA’s ability to help species recover.

“Our study makes an important point: It costs money to save endangered species — money to identify which species are in trouble and deserve special attention, money to protect and restore habitats, money to eliminate other threats like harmful invasive species. These endangered species can’t save themselves,” said co-author David Wilcove, professor of Ecology and Evolutionary Biology and Public Affairs and the High Meadows Environmental Institute at Princeton University.

The best way to increase the efficacy of the Endangered Species Act is to ensure that the relevant agencies have the funds they need to do what needs to be done. Full stop. – David Wilcove.

The findings are particularly newsworthy in light of the upcoming meeting of the United Nations Convention on Biological Diversity in December. The meeting aims to finalize a framework that will guide conservation efforts around the world through 2030. The planet currently faces accelerating rates of species extinction, with a projected loss of over 1 million species in the foreseeable future.

“It's a sad testimony regarding the state of U.S. leadership on this issue as we go into the next round of international talks on global biodiversity,” said co-author Andrew Dobson, professor of  Ecology and Evolutionary Biology at Princeton. “Nations need to commit more funds to saving threatened species and biodiversity in general, which also serves as a hedge against climate change and could create many other societal benefits, including jobs," said Dobson.

A persistent pattern

red knot on rocky shoreline

The Red Knot (Calidris canutus rufa) was added to the threatened list in 2014 after populations had declined markedly for several decades. Credit: Dan Liang, Center for Policy Research on Energy and the Environment, Princeton University

Small populations are more vulnerable to environmental and genetic threats, and thus more likely to go extinct before conservation interventions can recover the species to a stable population size.

Wilcove and colleagues first reported evidence in a 1993 study that species were not receiving protection under the ESA until their populations had become very small. At the time, species listed for protection had, on average, just 1,075 remaining individuals for vertebrate species, 999 remaining individuals for invertebrate species, and 120 remaining individuals for plant species.

The new study repeats the 1993 study’s methodology to determine whether the U.S. Fish and Wildlife Service has become more proactive during the roughly 30 years since attention was first drawn to the problem. They find that species’ population sizes at time of listing did not significantly change between 1985-1991 and 1992-2020.

The study also finds that there are consistently long “wait times” — the length of time between when a species is first identified as potentially needing protection and when it actually receives protected status under the ESA — which further increases the risk of extinction to species with already small or rapidly declining populations.

While funding allocations declined between 2010 and 2020, the number of species listed for protection increased by over 300% during that time. As a result, the study found that funding for protection has dropped by nearly 50% per species since 1985.

“It’s sad to see how little has changed over the last three decades,” said Wilcove. “We have a lot of species in serious danger of extinction in the United States. Looking ahead, we should aspire to protect species before they become so rare. Early action greatly increases the probability of success.”

As the meeting of the Convention on Biological Diversity draws near, the study authors hope that leaders in the U.S. and across the world will learn from these lessons to better protect and conserve imperiled species across the globe. 


The paper “Too few, too late: U.S. Endangered Species Act undermined by inaction and inadequate funding” first appeared in PLOS ONE on October 12, 2022. The study’s lead author is Erich Eberhard (Columbia University) with co-authors David Wilcove (Princeton University) and Andrew Dobson (Princeton University and the Santa Fe Institute).

This story was adapted from a news release written by Columbia Climate School with Keely Swan, Center for Policy Research on Energy and the Environment at the Princeton School of Public and International Affairs.