October 1, 2011 — andyextance

Warming temperatures will force creatures to journey in search of cooler areas to call home, but some are set to be trapped and endangered by short-term climate changes. That’s according to Dov Sax and Regan Early who have devised a way of understanding such “range shifts” in detail in research carried out at Brown University in Providence, Rhode Island. Their “ecological niche modelling” approach looked at 15 types of salamanders, frogs and newts that are set to move from California northwards towards Oregon as the US gets hotter. “Six of the 15 species we studied became trapped in less than half of their potential habitat by the year 2100,” Early told Simple Climate. “Four of these are likely to become endangered because of this. This is startling since these species are far from endangered at the moment.”

“Over the past ten years or so, scientists have realised that climate change will force many species to move to new ranges, where the climate is suitable for them, often dozens or hundreds of miles away,” Early explained. Most of this research assumes steady climate change, but in reality there will be periods when these changes speed up and slow down. This is especially true of the western coast of the US that the Brown researchers were interested in, Early noted. “In this region the climate is strongly driven by the Pacific Decadal Oscillation,” she said. “That means that temperature and precipitation might change strongly for one decade, then in another go back to being similar to historic conditions.”

Species are likely to colonise new areas during warm periods, and pause or temporarily retreat during cool periods. It’s wasn’t previously clear that creatures will be able to get to the location that will suit them best in the future through this “two steps forward, one step back” process, Early said. “We don’t really know whether species will be able to move to these new ranges,” she underlined.

Climate path

Early and Sax study whether such epic journeys could see the amphibians reach their promised lands in a paper published in scientific journal Ecology Letters on Wednesday. To do this they exploit general circulation models that produce some of the most authoritative global climate change predictions, adapted so that they give better information on local scales. “We used ecological niche models, that use the locations in which species are found and the climate at those locations to measure each species’ climatic requirements,” Early said. “Once we have that we can make maps that forecast these species’ ranges at multiple points in the future. When you overlay these maps you get the ‘climate path’ that species will need to follow.”

Their models showed that the 15 species, which are only found in the western US, face tough times. For example, they suggested that the speckled black salamander might not be able to shift into its full potential future range. Climate variability after 2050 causes the landscape connecting northern California and southern Oregon to become suitable for them only briefly. That means that there isn’t enough time for the entire population to pass through the area.

“We found that climatic fluctuations could stop species from being able to find new habitat under climate change,” Early said. “That’s even before you start to consider all the other things that might cause problems, like the landscape being intensely modified by people, as is the case in large urban or agricultural areas. Species move forward during the decades when climate is getting warmer, but during the decades when climate gets temporarily cooler the species get knocked back to where they came from. Every time climate warms again they have to make up all that lost ground, and all the while their current ranges are becoming more and more unsuitable for them.”

Robust forecasts

Early, who now works at the University of Évora in Portugal, underlined that this approach provides an important tool for conservationists, though it stops short of exact predictions. “Climate is so complicated that forecasts aren’t detailed enough to be able to map these climate paths precisely,” she acknowledged. Knowing more about how able species are to disperse and survive as climate changes would help improve them, she noted. But the fact that several models provide similar results shows they are already robust. “Whilst we can’t tell you exactly where species will move and when, we are confident that we’ve identified some of the biggest threats to these movements,” Early said.

Now that those threats have been demonstrated, humans can help ensure the amphibians don’t become endangered. This can be done by taking steps to reduce the impact of climate change, or removing other threats like predators and competitors, the researchers write. Other alternatives include improving habitat quality and the links between different areas and captive breeding programmes or moving individuals to boost population size or genetic composition. Without such steps, their survival is all down to how hardy they already are when the climate takes a turn for the worse, Early noted. “If species are able to persist during these decades of unsuitable climate at the point of the climate path that they’ve reached, then they don’t have as far to travel when climate warms again,” she said. “If they can’t persist like this then they are in trouble.”