As the climate shifts, many species will migrate to more favorable destinations, altering their natural range. However, researchers have found that the journey itself may be perilous and the path to a new habitat could fall apart, meaning some organisms may not make the transition to a new home.

Scientists at Brown University studied 15 amphibian species in the Pacific Northwest, including the black-bellied slender salamander, the Santa Lucia Mountains slender salamander, the California red-legged frog and the California newt. The researchers, Regan Early and Dov Sax, examined amphibians because they have distinct habitats. In addition, climate impacts on frogs, toads and salamanders are well-understood.

Using computer simulations, the researchers modeled species' ranges with climate projections over several decades, marking out areas where the organisms could feasibly live. By comparing current ranges with projections, Early and Sax could see whether ranges were contiguous and if the organisms could migrate. "We are really interested in the process by which species move from where they live now and where they will live in the future," said Early, now a postdoctoral researcher at the University of Évora in Portugal.

In its recent paper in Ecology Letters, the team concluded that eight of the 15 species studied would become endangered or go extinct. One of the main reasons for this is that the favorable climate paths to new environments are inconsistent, varying in size with the average temperature.

"As we move from the temperature we're at to warmer temperatures, it could be a smooth line or temperature change could be bouncing all around," said Sax, assistant professor of ecology and evolutionary biology at Brown. "You could have a situation going forward where the decade is actually cooler than the decade that preceded it. It's those sort of dynamics that interplay with the maximum speed those species can move."

The fluctuating temperature can shrink amphibian habitats, effectively trapping them in pockets en route to more stable environments. Thus, a species' survival depends not only on access to favorable pathways, but also on its resilience and resistance to climate changes.

Running gantlets toward survival
"It was a real surprise to us actually that species may not be able to move along these paths," said Early. "Warming and cooling creates a 'two steps forward, one step back' problem."

Sax said this research has implications beyond amphibian wildlife. When rain patterns change and temperatures rise, a number of species will feel pressure to migrate, but will face obstacles beyond geography and development. "For me, one of the most interesting things in thinking about biological conservation is that biological corridors -- large extents of land that connect reserves -- are often ineffective," he said. "It's potentially big news for conservation biology and conservation planning."

In addition, not all wildlife is equally vulnerable to climate change. "There are some [species] that have a harder time dispersing," said Sax. "The worst off are things that only live in isolated environments, like lakes or mountaintops."

One alternative to creating conservation corridors is managed relocation, where organisms are deliberately collected and moved to a new habitat. This approach, however, brings its own problems. "It's very controversial," said Early. "Every time we've moved species in the past, there have been disastrous results. It's very difficult to predict how they might perform, and they can become invasive species."

Early said the next step is to quantify how effective different conservations methods would be in order to chart a path forward for ecosystems affected by climate change, controlling for more variables and studying more species. "Everything in these landscapes will be changing in the next hundred years," said Early.

Reprinted from Climatewire with permission from Environment & Energy Publishing, LLC., 202-628-6500.