MISSOULA — On Wednesday the U.S. Fish and Wildlife Service declared 23 species of birds, fish, and other species extinct.
Probably the most famous species on the list is the Ivory-Billed Woodpecker, which some thought had been seen in the swamps of the southern U.S. in recent decades.
The U.S. government is declaring the splendid ivory-billed woodpecker -- and 22 more birds, fish and other species-- extinct.
It's a rare move for wildlife officials to give up hope on a plant or animal, but government scientists say they've exhausted efforts to find these 23.
And they warn climate change, on top of other pressures, could make such disappearances more common as a warming planet adds to the dangers facing imperiled plants and wildlife.
The factors behind the disappearances vary - too much development, water pollution, logging, competition from invasive species, birds killed for feathers and animals captured by private collectors. In each case, humans were the ultimate cause.
Another thing they share: All 23 were thought to have at least a slim chance of survival when added to the endangered species list beginning in the 1960s.
Only 11 species previously have been removed due to extinction in the almost half-century since the Endangered Species Act was signed into law.
Wednesday's announcement kicks off a three-month comment period before the species status changes become final.
Around the globe, some 902 species have been documented as extinct. The actual number is thought to be much higher because some are never formally identified, and many scientists warn the earth is in an "extinction crisis" with flora and fauna now disappearing at 1,000 times the historical rate.
It's possible one or more of the 23 species included in Wednesday's announcement could reappear, several scientists said.
A leading figure in the hunt for the ivory-billed woodpecker said it was premature to call off the effort, after millions of dollars spent on searches and habitat preservation efforts.
What's lost when those efforts fail are creatures often uniquely adapted to their environments. Freshwater mussel species like the ones the government says have gone extinct reproduce by attracting fish with a lure-like appendage, then sending out a cloud of larvae that attach to gills of fish until they've grown enough to drop off and live on their own.