" " A Hawksbill sea turtle swimming off the coast of Australia. Mark Kolbe/Getty Images

Back in 1973, out of concern that many of America's native plants and animals were in danger of extinction, Congress passed the Endangered Species Act. The law enables regulators to designate species as either "endangered," meaning that they're at risk for becoming extinct throughout at least a significant portion of their range, or "threatened," meaning that they're likely to become endangered in the near future. Once plants and animals are on the list, they can't be harmed or harvested, and their habitats can't be modified or damaged in a way that kills, injuries or impairs their ability to breed, feed, take shelter or perform other functions necessary for existence.

While environmentalists have viewed the law as a milestone, mining and agribusiness interests long have considered it too restrictive. The Trump Administration recently has sought to change the way the law is applied to reduce what it considers burdensome protections for threatened species.



But the Act's defenders may get a boost from a study by Abel Valdivia, Shaye Wolf and Kieran Suckling of the Center for Biological Diversity in Tucson, Arizona, published January 16 in the journal PLOS ONE. The researchers, who looked at 31 different populations of marine mammals and sea turtles, found that 78 percent of the mammals and 75 percent of the turtles increased their population size after receiving protection under the Act. Just 9 percent of marine mammal populations — and no sea turtle populations — decreased after receiving legal protection.

Sea turtles in particular benefited from the law, with their populations increasing by 980 percent. Even more impressive was the resurgence of Hawaiian humpback whales, which increased from just 800 animals in 1979 to more than 10,000 in 2005. The species recovered so much that regulators were able to remove it from the endangered list in 2016.

"The Endangered Species Act not only saved whales, sea turtles, sea otters and manatees from extinction, it dramatically increased their population numbers, putting them solidly on the road to full recovery," Wolf said in a press release. "We should celebrate the Act's track record of reducing harms from water pollution, overfishing, beach habitat destruction and killing. Humans often destroy marine ecosystems, but our study shows that with strong laws and careful stewardship, we can also restore them, causing wildlife numbers to surge."