What is the difference between an endangered species and a threatened species?

Properly designating a species as threatened or endangered can ensure its protection and longevity.

The bengal tiger is an endangered species (Photo: Aditya Singh/Getty Images)

The Endangered Species Act, enacted by Congress in 1973, defines an endangered species as "any species which is in danger of extinction throughout all or a significant portion of its range." The ESA defines a threatened species as "any species which is likely to become an endangered species within the foreseeable future throughout all or a significant portion of its range."

In other words, endangered species are plants or animals on the brink of extinction now, while threatened species are likely to be on the brink in the near future. According to the U.S. Environmental Protection Agency, there are approximately 2,000 endangered or threatened species in the U.S. today.

How do species become endangered or threatened?

Most of the listed species got into trouble because of human influence, through hunting, habitat destruction, or the introduction of nonnative invasive species. Though animals and plants have gone extinct throughout all of Earth’s history, the rate of extinction is rapidly increasing.

Who makes the decision to list a species?

The U.S. Fish and Wildlife Service decides which species get listed as threatened or endangered, often in response to a petition by an environmental group. (The National Oceanic and Atmospheric Administration is responsible for listing marine species.) To do so, the agency considers a handful of criteria, such as what percentage of the species’ critical habitat has been degraded or destroyed and whether the species has been over-depleted by commercial, recreational, scientific, or educational uses. Biologists also determine if the species is threatened by disease or predation, if current regulations or legislations inadequately protect the species, and if other human-caused factors threaten the long-term survival of the species.

What happens after a species is listed?

The wood stork was downgraded from endangered to threatened in June 2014.

(Photo: Getty Images)

When a species makes it on the list, it is protected by federal law and can’t be harassed, moved, trapped, killed, or wounded by people. The primary goal of this strict protection is to restore sustainable populations of the species so it can eventually be delisted.

Have species been removed from the list?

Recently, there have been a handful of endangered species success stories. In August 2008, the Virginia northern flying squirrel was delisted after being protected since 1985. In 2011, most gray wolf populations were removed from the list. Gray wolves’ numbers dwindled to just a few hundred in the continental U.S. during the 1950s. But thanks to concentrated efforts to boost its breeding and increase its habitat, the species is poised for a comeback, though environmentalists are fighting efforts by ranchers and state officials to remove the wolf from the endangered species list.

As of September 2012, fifty-six species have been delisted. Twenty-five others have been downgraded from endangered to threatened status. 

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