A comprehensive survey of lizards on islands around the world has confirmed what island biologists and seafaring explorers have long observed: Animals on islands are much more abundant than their counterparts on the mainland.
Besides confirming that longstanding observation, the study signals an alarm for island populations in a rapidly warming world. It suggests that climate change may have devastating consequences for lizards and other animals that inhabit islands because their ecosystems are much more sensitive than those on the mainland to change.
Details of the study conducted by biologists at the University of California, San Diego will appear in a paper slated for publication in the June issue of the journal Ecology Letters, available online in May.
We found that island populations are less resistant to biological invasions, which will likely increase dramatically with changing climate, says Walter Jetz, an assistant professor of biological sciences at UCSD and a co-author of the study.
Climate change will drive animals to move to new places, says Lauren Buckley, a postdoctoral fellow at the Santa Fe Institute who is a visiting scholar at UCSD and the other co-author of the study. Our research suggests that those animals that move to islands can strongly affect the sensitive animal communities on islands.
In addition to their increased sensitivity to biological invasions, populations on islands are more vulnerable than those on the mainland to sea level rise and increased storm activity, which are expected by many scientists to become worse as a result of global warming.
Jetz and Buckley gathered 643 estimates of lizard abundance from around the world for their survey, the first extensive global study of island densities for any animal group. Analyzing these estimates, they determined that lizards were consistently more than ten times more abundant on islands than on the mainland.