Study sheds new light on extinction rates of species on islands

Washington, August 27 : A new research has shed surprising light on the subject of extinction rates of species on islands, suggesting that diversity among animals on islands is on the rise.

It's no secret that humans are having a huge impact on the life cycles of plants and animals.

UC (University of California) Santa Barbara's Steven D. Gaines and fellow researcher Dov Sax decided to test that theory by studying the world's far-flung islands.

"The presumption at the time was that we are driving biodiversity to lower levels," said Gaines, who directs UCSB's Marine Science Institute. "Certainly, if you think about it at the global level, this is true because humans have done a lot of things that have driven species extinct," he added.

However, when studied on the smaller scale of islands, the findings showed something completely different. Diversity is on the rise - markedly so in some instances.

Diversity has gone up so dramatically that it might cause some to wonder if the health of the ecosystems might not be better because the number of species is twice as high as it used to be.

"What Dov and I worked on a few years ago is the fact that the vast majority of introductions (of species) don't have large negative effects," said Gaines.

"Indeed, most species that get introduced don't have much effect at all. It doesn't mean that they're not altering the ecosystem, but they're not driving things extinct like some of the big poster-child stories we've been hearing about," he added.

Sax, a former postdoctoral researcher at UCSB, who is now assistant professor of ecology and evolutionary biology at Brown University, did much of the fact-finding for this report by digging through data that had been collected over hundreds of years on islands around the world.

"The dramatic increase in the number of species has changed how the system functions," Sax said.

"Changing the abundance of natives versus exotics affects all of the other species that used to depend on the natives for food or shelter. So, it's not in any way to say that increasing biodiversity is a good thing," he added.

The study showed that human colonization has had a massive impact on ecosystems of islands, with the introduction of new, exotic plants and animals.

According to Sax, about 40 percent of the species of birds that are found on islands today are introduced species, which means that a comparable number of birds has gone extinct.

"In the case of birds, lots of extinctions, no change in total biodiversity," he said.

ANI