Their recent message says we are now witnessing the greatest extinction crisis since dinosaurs disappeared from our planet 65 million years ago.
While critics might counter that IUCN is engaging in hyperbole, claiming that extinction is part of the natural cycle, conservationist Scott McRobert, Ph.D., professor of biology at Saint Joseph's University in Philadelphia, Pa., says the urgent tone of the message is accurate, and the current mass extinction has little in common with the prehistoric event. So what is different?
"Human beings are the cause of this crisis. Almost everything humans do that causes damage to the Earth - polluting, introducing alien species, causing global climate change, sport hunting, commercial hunting and poaching - contributes to the loss of species," he says.
McRobert adds that the biggest cause of extinction is habitat destruction: cutting down forests, draining wetlands, and replacing natural areas with housing developments, roads or farms.
A geneticist who also studies animal behavior, McRobert houses several assurance colonies of endangered species in his biodiversity lab at SJU. Of particular interest is his colony of 13 Vietnamese leaf turtles - Mauremys annamensis - a small turtle once abundant in central Vietnam.
"This species is listed as critically endangered, but may very well be extinct in the wild, which means no individuals exist in the natural world," says McRobert. "It has been decimated by habitat destruction and hunting for food, which demonstrates the limitations of attempts to save a species."
McRobert adds that leaf turtles are relatively easy to keep and breed in captivity. "There are quite a few individuals alive in captivity. We study them to learn more about the species, and breed them to increase the size of the remaining population, but we also must ask, 'what's the point?' since there are no safe places for them to be released into the wild."
But McRobert is hopeful that the leaf turtle - and many other species - will not go the way of the dinosaur. "Scientists are playing a waiting game," he says. "Though we don't know if it will ever happen, we are trying to keep species alive long enough to someday reestablish populations to nature."