Anthropologist Predicts Major Threat To Species Within 50 Years

"If other species follow the same pattern as the mammals and birds in our study, then we are facing a serious threat to global biodiversity associated with our growing human population."

The prediction, carried in a paper published in the journal Biological Conservation, arose from an effort by McKee to separate the effects of the numbers of humans from questions about how they use – or abuse – the environment.

McKee, an associate professor of both anthropology and of evolution, ecology and organismal biology at the university, was seeking a direct correlation between population growth and the number of threatened species. To do so, he had to balance the size of each country against the number of people living within its borders in order to develop an accurate population density.

"We knew that there are a number of natural components (that can affect species vulnerability)," he said. "We wanted to put all of the countries in the study on a level playing field in terms of their particular environments and the number of species present."

Once they combined the natural factors together with the human factors and did the tabulations, McKee says the result was an 88 percent predictability of how many species would be threatened if human population continued to grow.

The remaining 12 percent, he says, is explainable using other variables, such as the number of endemic species in a specific country as well as differences in patterns of human behavior. The greater the diversity, he said, the more likely his estimate could be wrong because of the greater number of species still unknown to science.

McKee's prediction that the United States would face 10 additional threatened species in the next half-century may seem minimal, he said, but it isn't.

"The loss of an additional 10 species of mammals and birds doesn't sound like a lot but it really is," he said. "Remember, it takes hundreds of thousands of years for a new species to arise. We're saying that it may only take 50 years for 10 of them to reach the brink of extinction."

McKee emphasized that this predicted additional 10 species at risk does not include the current rate of disappearing species the world now faces.

"In our study, we only looked at species of mammals and birds," he said. "We didn't include the countless species of insects and other life forms, many of which are relatively unknown, in this analysis."

McKee sees the loss of these mammals and birds as a kind of "canary in a coal mine" phenomenon, a warning of the impact on the environment.

"We have no way of knowing before it is lost if one particular animal is a 'keystone' species – one upon which countless others depend," he said.

To reach his conclusions, McKee started with data on 230 nations. He excluded island nations and those whose small size forced an unusual population density. Other nations, such as the former Soviet block, were excluded for lack of precise data. In the end, he used a list of 114 countries worldwide.

He linked the total numbers of known mammals and birds from international databases with the IUCN (International Union for Conservation of Nature and Natural Resources) Red List of Threatened Species. To this he added the U.S. Census Bureau's current data on human population and its projections for world population growth. Climatic data such as annual precipitation and temperatures were factored in as well.

His study pointed to the Congo as having the worst future – an estimated addition of 26 threatened species by the year 2050, an increase of 39.8 percent. At least 100 of the 114 nations covered in the study showed a possible increase in the number of threatened species. Another 10 nations should have a decrease in the number of threatened species by 2050, because of their individual declines in human population, he said.

"The density of people is a key factor in species threats," he says, "depending upon the ecological nature of a nation and the number of species 'available' for the threat of extinction.

"If other species follow the same pattern as the mammals and birds in our study, then we are facing a serious threat to global biodiversity associated with our growing human population."