Species displaced by climate change face unexpected obstacles

Contributing Writer
Friday, September 30, 2011

As climate change affects many animals’ habitats, conservationists, environmentalists and scientists are becoming increasingly concerned about their ability to survive environmental disruptions. In a yearlong study that began in early 2009, Dov Sax, assistant professor of biology, found unexpected obstacles to the migration paths 15 amphibian species are likely to take as climate change worsens.

Sax conducted the research with Regan Early, now a post-doctoral fellow at the University of Evora in Portugal. Their article, “Analysis of climate paths reveals potential limitations on species range shifts,” states that climate change will force many species to seek out new homes as their original environments become increasingly unsuitable to their survival.  

To study these organisms’ ability to make the transition, Sax and Early constructed a “climate path” for each species of amphibians. This projected migrational route predicts where each amphibian would travel over the next few decades and when it would inhabit a particular area.

Sax and Early constructed these climate paths using a variety of models, including climate models that predict how an environment is going to change over time and climate niche models, which examine the current habitats of a species to determine “the set of conditions it can tolerate,” Sax said.

Originally, Sax and Early “expected to find that cities and large areas of human impact on the landscape would stop species from shifting their ranges,” but during their initial research, they began looking more closely at natural “gaps” as a major obstruction to these climate paths, Early said. These “gaps” are areas of climatic instability that a species is projected to travel through.

“Once we discovered this effect, we realized that it was so important because it was so fundamental and would be affecting species all over the world. We decided to stop studying the effects of cities and human impact on the landscape and focus on this much more fundamental question,” Early said.   

“Instead of getting steadily warmer, climate might get a few degrees warmer and then one degree cooler. Because it is always getting warmer and cooler, species will move into the areas when it gets warmer, but then they will disappear from that area when it gets cooler again. So it’s like taking two steps forward but one step back,” Early said.

Sax and Early also found that both a species’ persistence and its “dispersal-ability” positively correlated with its capacity to migrate successfully down its “climate path.” According to the article, persistence is a species’ capacity to withstand “short-term unfavorable climate conditions.” Dispersal-ability is the distance an organism can travel from its niche.  

This is the first time that “the importance of persistence under short-term unfavorable climate conditions has been quantified,” according to the article. Due to the lack of existing information in this area, more research must be done to understand various species’ persistence-levels, Sax said.

Sax and Early both said they consider their research a precursor to possible future areas of study related to climatic gaps, persistence and dispersal abilities.

“We have the technology now to be able to map the climate paths that species will move along from where they live now to where they can live in the future. So we’re suggesting that people should do this a lot more widely and start to become much more aware of the actual processes that will help species move or not,” Early said.

The study also has many implications for animal conservationists. Currently, habitat corridors — which are set up to ensure that the land between two different niches is traversable for migrating species — are among the most common methods of helping animals move from one environment to another.

But Sax said he believes climate gaps will reduce the effectiveness of habitat corridors.  

“I think what our work shows is that (habitat corridors) won’t work well for as many species as was originally thought. So it’s not going to be as powerful as a strategy as people had hoped,” Sax said.

One alternative that Sax and Early considered is the heavily debated “managed relocation” option, where humans transport species from one location to another.

There is concern that managed relocation may contribute to the growth of invasive species, Early said. Despite this, Sax said he sees it as a viable option for the future.            

“If we want to have populations that live in the wild, then (managed relocation) is going to be our only option for some species,” Sax said.

Currently, Sax is leading a working group of roughly 35 lawyers, politicians, activists and researchers who are examining the scientific, ethical, economic and legal issues related to managed relocation. He said he expects to finish his work with the group within a year, possibly producing results that will help the general public come to a greater consensus on the topic.

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