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. However, the law has resulted in relatively few successes in helping species recover. 

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. 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.

“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 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.