This week the US government declared the ivory-billed woodpecker and 22 species extinct. They were officially removed from the endangered species list because they hadn’t been documented in the wild for many years.

The loss of the species was hailed by many as a consequence of human population growth and the attendant loss of natural habitats and growth in pollution, as well as the climate crisis.

But the move was also questioned by some experts who say it’s too soon to remove the protections that come with the endangered designation. And it is possible that some of the species could still pop up again, like the biblical Lazarus, rising from the dead.

Scientists have been on the hunt for the ivory-billed woodpecker ever since a kayaker apparently spied one in southern swamps in 2004. Millions of dollars have been spent on searches – and just as importantly for many other species preserving the bird’s potential habitat.

The ivory-billed woodpecker is an icon, and a representative of the major old-growth forests of the south-east, John Fitzpatrick, a biologist who authored a study that claimed the bird had been rediscovered in eastern Arkansas, told the AP. “Keeping it on the list of endangered species keeps attention on it, keeps states thinking about managing habitat on the off-chance it still exists.”

US Fish and Wildlife officials released an analysis Wednesday stating that there have been no definitive sightings of the woodpecker since 1944 and “there is no objective evidence” of its continued existence.

The wildlife service says that delisting the woodpecker – and the 22 other species, including a fruit bat, birds from Pacific islands and freshwater mussels – frees up resources to devote to species that may still recover from threats.

Conservation is certainly expensive. A 2016 study by the Center for Biological Diversity found that Congress only provides about 3.5% of the funding that the Fish and Wildlife Service’s own scientists estimate is needed to recover species. Roughly one in four species receives less than $10,000 a year toward recovery. Joe Biden has yet to nominate a director for the Fish and Wildlife Service, though he did request a more than $60m increase for endangered species – the largest increase requested for the program in history.

The vast majority of species under federal protection – 99% – have not gone extinct. And since 1975, 54 species have left the endangered list after recovering, including the bald eagle, brown pelican and most humpback whales. However, these success stories represent only about 3% of those on the list.

The International Union for Conservation of Nature, a Switzerland-based group that tracks extinctions globally, is not putting the ivory-billed woodpecker into its extinction column because it’s possible the birds still exist in Cuba. The group’s Red List still designates the birds as “critically endangered” but not extinct.

The group notes that despite historical declines, the woodpecker’s habitat throughout the south-eastern US is recovering as previously cut forests mature. However, habitat loss and potential hunting in Cuba may pose a threat to any remaining individuals within the Cuban subpopulation.

Many recreational birders agree that the search is not over. Derek Sallmann, who runs a popular YouTube channel devoted to birding, told his viewers it’s a terrible idea to delist the species. “They have nowhere near exhausted efforts to find the ivory-billed woodpecker,” he says. “There’s so much unsearched area, there’s so much land out there. By declaring the species extinct it’s just going to fall off people’s radar and then a lot of the habitat can be destroyed.”