Survival of the fit, fast and persistent?

Climate variability adds another hurdle for amphibian species trying to migrate to more suitable habitats to escape the impacts of global warming.

As the climate warms, species that cannot adapt to local conditions may be able to survive by migrating to more suitable habitats elsewhere. Along the way, these species will face many perils posed by fragmented and human-dominated landscapes.

Image Credit: Rainforest Harley

In a study published in the November 2011 issue of Ecology Letters, scientists discovered that migrating species may be hindered by climate variability, and that their chances for survival will hinge largely on their ability to either disperse quickly into new habitats or to persist for many years during unfavorable weather conditions.

To conduct their research, the scientists used well-known climate forecasting models (the Hadley CM3 Model and the Parallel Climate Model) to examine the projected “climate paths” of fifteen amphibian species in the western United States to the year 2100. They chose to evaluate frogs, toads and salamanders whose susceptibility to temperature changes are thoroughly understood.

Their data indicate that by 2100 four of the fifteen amphibians will likely become extinct, four others would become endangered and that only seven of the original fifteen species will be able to adequately make the transition to an altered climate. Specifically, the scientists discovered that temperature swings can cause a migrating species to be stopped in its tracks, and that the ability of a species to persist during unfavorable weather conditions may be just as important as dispersal speed at predicting extinction risks.

Dov Sax, an assistant professor at Brown University, stated in a press release:

Our work shows that it’s not just how fast you disperse, but also your ability to tolerate unfavorable climate for decadal periods that will limit the ability of many species to shift their ranges. As a consequence, many species that aren’t currently of conservation concern are likely to become endangered by the end of the century.

The speckled black salamander could expand its current range (orange) into new territory (gray). However, climate variability may put the new areas beyond the salamander’s reach. Image Credit: Sax Lab, Brown University.

The paper was the first to explicitly look at persistence as a factor that can impact the success of species migrations during climate change. An improved understanding of the intrinsic traits that allow for species to survive in a changing climate will enable science to better identify species at risk for extinction and to design appropriate conservation practices.

Image Credit: rikidesignPhoto

Dov Sax and his co-author Regan Early, a post-doctoral fellow at the Universidade de Évora in Portugal, have been studying the response of species to climate change, with a particular emphasis on understanding and preventing species extinctions. They believe that wildlife managers may need to start seriously considering the use of a controversial practice called managed relocation to help prevent species extinction due to climate change.

Managed relocation is a conservation practice that involves physically assisting species in their migration into new, more suitable habitats. The practice is hotly debated due in part to well-founded concerns over the unintended consequences that can result when an exotic species is introduced into a new habitat. On the other hand, leaving the future of biodiversity up to species that are fit, fast and persistent is a pretty tall order.

Sax commented further in the press release:

This study suggests that there are a lot of species that won’t be able to take care of themselves. Ultimately, this work suggests that habitat corridors will be ineffective for many species, and that we may instead need to consider using managed relocation more frequently than has been previously considered.

Funding for the research on species range shifts due to climate change/global warming was provided by Brown University, the U.S. Forest Service and the Portuguese Foundation of Science and Technology.

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