The endangered species list is full of ghosts

The International Union for Conservation of Nature, which organizes the international species lists, declared the Scioto madtom extinct in 2013. It had last been seen alive in 1957. But the United States still classifies the catfish as endangered, despite the U.S. Fish and Wildlife Service—the federal organization in charge of the endangered species list—agreeing that the fish is gone. Without clear incentive to delist the Scioto madtom, yet also without proof that there are any left to save, the catfish has drifted into extinction purgatory.

The fate of future endangered species could hinge on a semantic argument

Everyone agrees that the Pacific walrus is stressed. The large, tusked pinnipeds depend on floating sea ice to rest and give birth in the spring and summers, when the Goldilocks-sized not-too-thin, not-too-thick ice floes they require are becoming increasingly rare. But coming to a consensus on how the large marine mammals will react to that stress is less straightforward.