"Up to 50 percent of species are predicted to be lost in the next 50 years," they added. "Current extinction estimates need to be recalibrated by taking species coextinctions into account."

The team, led by Lian Pin Koh and Navjot Sodhi of the National University of Singapore, compiled a list of 12,200 plants and animals currently listed as threatened or endangered. They then looked at insects, mites, fungi and other organisms that are uniquely adapted to some of the species.

"What we found is that with the extinction of a bird, or a mammal or a plant, you aren't just necessarily wiping out just one, single species," said Heather Proctor from the University of Alberta in Canada, who also worked on the study.

"We're also allowing all these unsung dependent species to be wiped out as well."

For example, a vine that became locally extinct in Singapore took along with it a species of butterfly, Parantica aspasia, that was dependent on the vine for survival.

"When we lose this vine, this beautiful butterfly dies off with it, and we'll never see it again except in photographs at museums," said Proctor.