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Climate warming accelerates Arctic migration for some species

Doug O'Harra

Climate warming has been driving animals and plants toward the poles at a rate three times faster than previously thought — and pushing them higher in elevation about twice as fast, according to a new study that examined the response of some 2,000 species to global warming over the past half century.

The research, conducted by a team based at the University of York, also demonstrated for the first time that these plants and animals have shifted their habitat in direct response to rising temperatures and not some other factor.

"This research shows that it is global warming that is causing species to move towards the poles and to higher elevations,” said lead author I-Ching Chen, former a PhD student at York and now a researcher at the Academia Sinica in Taiwan, in this story posted by York. “We have … shown that the amount by which the distributions of species have changed is correlated with the amount the climate has changed in that region."

In some ways, it’s all about chasing the ecological sweet spots — those Goldilocks niches with just right temperatures, seasonal rhythm and food sources — as they keep drifting further north (and south) and farther up (or down) the slopes in the face of climate change.

"These changes are equivalent to animals and plants shifting away from the Equator at around 20 cm per hour, for every hour of the day, for every day of the year,” added Chris Thomas, Chen’s advisor and Professor of Conservation Biology at York, in the same story. “This has been going on for the last 40 years and is set to continue for at least the rest of this century.”

No Alaska species were include in the analysis, but Thomas says that his team’s results would definitely apply to Alaska and the entire Arctic.

“The high Arctic is already warming faster than other parts of the world, and is expected to continue to do so,” he told Alaska Dispatch in an email. “Thus, the changes in Alaska are likely to have been even greater than the averages we report in our Science article.”

Rapid Range Shifts of Species Associated with High Levels of Climate Warming," published this week in Science, examined hundreds of previous studies documenting how animals and plants have been shifting their ranges from the middle of the 20th century through the past decade.

“The researchers brought together all of the known studies of how species have changed their distributions, and analysed them together in a ‘meta-analysis,’” according to York story. “The changes that were studied include species retreating where conditions are getting too hot (at low altitudes and latitudes), species expanding where conditions are no longer too cold (at high altitude and latitudes), and species staying where they are but with numbers declining in hotter parts and increasing in cooler parts of the range.”

Only by looking at the mass of studies could the scientists detect the global patterns, explained co-author Jane Hill, Professor of Ecology at York.

"It's a summary of the state of world knowledge about how the ranges of species are responding to climate change,” she said here. “Our analysis shows that rates of response to climate change are two or three times faster than previously realised."

Finding species on the move to avoid rising temperatures

Although most species examined live in Great Britain, other locales covered the gamut — from the mountains of Madagascar to the European Alps, from Yosemite to Finland, from coastal tide pools of Chili to coastal waters along Portugal. Existing research about Alaskan animals and plants were not included because they didn’t match the criteria the scientists followed.

“We only included studies where scientists had studied many species in the same place (to make sure that there was no possible bias in the choice of species), and we did not find any studies of this type from Alaska,” Thomas told Alaska Dispatch in an email. “So, we could not, for example, include the excellent work that is going on on polar bears, which are starting to suffer from warming; or the consequences of permafrost melting.”

But, Thomas added, “What I hear from Alaska is consistent with our results.”

The critters involved were diverse. Included were a menagerie of British butterflies, dragonflies, wood lice, spiders and harvestmen. The scientists looked at research into birds of the U.S. Great Plains, findings about reptiles and amphibians off the coast of Africa and the tracking of millipedes in England.

What they found was startling. Among 764 species across 23 groups that have moved further north or south in response to climate change, the average shift in latitude has been about 17.6 kilometers per decade — or just over one mile per year. Previous studies suggest species were moving only about 6 kilometers per decade.

Among 1.367 species from 31 groups that have moved higher or lower on mountains and hills, the average shift in elevation was about 12.2 meters per decade — or about four feet per year. That’s twice as far what was indicated in previous studies.

“We found that rates of latitudinal and elevational shifts are substantially greater than reported in a previous meta-analysis, and increase with the level of warming,” wrote the authors. 

The more it warmed, the further they moved

“The distances moved by species are greatest in studies showing the highest levels of warming, with average latitudinal shifts being generally sufficient to track temperature changes.”  

Not all species moved at the same pace, and some even retreated in the direction opposite of what you might expect, the scientists said. It’s complicated not only by temperature but also by what happens when their habitat heats up. Sometimes there’s no good place to move.

"In Britain, the high brown fritillary butterfly might have been expected to expand northwards into Scotland if climate warming was the only thing affecting it, but it has in fact declined because its habitats have been lost.,” explained co-author Dr David Roy, from the Centre for Ecology & Hydrology in the release from York. “Meanwhile, the comma butterfly has moved 220 kilometres northwards from central England to Edinburgh, in only two decades."

So certain groups of animals and plants acted differently, depending on how their ecological needs interacted with changes on the ground, the scientists said.

“Cetti's warbler, a small brown bird with a loud voice, moved northwards in Britain by 150 kilometres during the same period when the Cirl bunting retreated southward by 120 kilometres, the latter experiencing a major decline associated with the intensification of agriculture.”

With the help of Thomas, her Ph.D advisor at York, Chen had already produced some of the first evidence showing that climate warming was shifting tropical animals, in particular a family of moth species living on Mount Kinabalu, one of the highest mountains in Borneo. In “Elevation increases in moth assemblages over 42 years on a tropical mountain,” Chen and her seven co-authors gathered hundreds of the critters on the mountain slopes and found that 106 species of geometer moths had shifted their habitat an average of 67 meters uphill between 1965 and 2007.

Up to 10 percent of animals and plants face extinction

More work needs to be done before scientists can start predicting whether or how far any given individual species will move in the face of further climate change, the authors concluded.

The bottom line: Many animals and plants are being driven from their preferred habitats and increasingly face ecological trouble in their new homes.

“The current research does not explicitly consider the risks posed to species from climate change, but previous studies suggest that climate change represents a serious extinction risk to at least 10 per cent of the world's species,” the scientists said in the story.

Contact Doug O'Harra at doug(at)alaskadispatch.com