The ongoing global growth in the human population will inevitably crowd out（挤出，推开） mammals and birds and has the potential to threaten hundreds of species with extinction within 40 years, new research shows. Scientists at The Ohio State University have determined that the average growing nation should expect at least 3.3 percent more threatened species in the next decade and an increase of 10.8 percent species threatened with extinction by 2050.

The United States ranks sixth in the world in the number of new species expected to be threatened by 2050, the research showed.

Though previous research has suggested a strong relationship between human population density and the number of threatened mammal and bird species at a given point in time, this study is the first to link an expanding human population to fresh threats of extinction for these other species.

The lead researcher created a model based on 2000 data to forecast future threatened species connected to human population growth projections, and published the predictions in 2004. In this new study, that model's predictions were confirmed by 2010 actual figures. The scientists then used the same model, containing data on 114 countries, to extend their predictions to the middle of this century.

"The data speak loud and clear that not only human population density, but the growth of the human population, is still having an effect on extinction threats to other species," said Jeffrey McKee, professor of anthropology at Ohio State and lead author of the study.

The findings suggest that any truly meaningful biodiversity conservation efforts must take the expanding human population footprint into consideration -- a subject that many consider taboo.

"Our projection is based on human population density alone. It doesn't take into account climate change, industrialization or wars. So the actual numbers that we predict for 2050 will be very different because everything we do will exacerbate the problem," he said. "You can do all the conservation in the world that you want, but it's going to be for naught if we don't keep the human population in check."

McKee conducted the research with Ohio State undergraduate Julia Guseman and former graduate student Erica Chambers. The study is published this week in the journal Human Ecology.