Polar bears threatened: Experience limited energy savings in summer

A young polar bear stands on pack ice over deep waters in the Arctic Ocean in October 2009, during a major research project headed by the University of Wyoming.
Credit: Shawn Harper

Polar bears are unlikely to physiologically compensate for extended food deprivation associated with the ongoing loss of sea ice, according to one-of-its-kind research conducted by University of Wyoming scientists and others, and published today in the journal Science.

“We found that polar bears appear unable to meaningfully prolong their reliance on stored energy, confirming their vulnerability to lost hunting opportunities on the sea ice — even as they surprised us by also exhibiting an unusual ability to minimize heat loss while swimming in Arctic waters,” says John Whiteman, the UW doctoral student who led the project.

The loss of sea ice in the Arctic, which is outpacing predictions, has raised concern about the future of polar bears, leading to their listing as a globally threatened species under the U.S. Endangered Species Act in 2008. The bears depend on hunting seals on the surface of the sea ice over the continental shelf, most successfully from April to July. In parts of the polar bears’ range, the lengthening period of sea ice retreat from shelf waters — caused by increasing temperatures — can reduce their opportunities to hunt seals, leading to declines in bear nutritional condition.

Some earlier research suggested that polar bears could, at least partially, compensate for longer summer food deprivation by entering a state of lowered activity and reduced metabolic rate similar to winter hibernation — a so-called “walking hibernation.” But the new research shows that the summer activity and body temperature of bears on shore and on ice were typical of fasting, non-hibernating mammals, with little indication of “walking hibernation.”

Whiteman and his colleagues concluded in theSciencepublication: “This suggests that bears are unlikely to avoid deleterious declines in body condition, and ultimately survival, that are expected with continued ice loss and lengthening of the ice-melt period.”

The researchers reached that conclusion by capturing more than two dozen polar bears, implanting temperature loggers and tracking their subsequent movements on shore and on ice in the Arctic Ocean’s Beaufort Sea, north of Alaska and Canada, during 2008-2010. The unprecedented effort, logistically supported by the U.S. Geological Survey (USGS) and funded by the National Science Foundation, USGS, U.S. Fish and Wildlife Service (USFWS), as well as the Environmental Protection Agency, required the assistance of numerous personnel, multiple helicopters and deployment of the U.S. Coast Guard ice-breaker, the Polar Sea.

“Many colleagues — even some on our research team — doubted whether the study was possible, until we actually did it,” says Merav Ben-David, the UW professor who developed the research plan along with Professor Hank Harlow, an eco-physiologist and colleague in the Department of Zoology and Physiology, and Steve Amstrup, previously with the USGS and currently the chief scientist at Polar Bears International. “This project was logistically so intense that it may never be replicated.”

At the same time, the scientists found that polar bears use an unusual physiological response to avoid unsustainable heat loss while swimming in the cold Arctic waters. To maintain an interior body temperature that allows them to survive longer and nowadays more frequent swims, the bears temporarily cool the outermost tissues of their core to form an insulating shell — a phenomenon called regional heterothermy.

“This regional heterothermy may represent an adaption to long-distance swims, although its limits remain unknown,” wrote the scientists, who in an earlier publication — in the journalPolar Biology— noted that one of the bears in the study survived a nine-day, 400-mile swim from shore to ice. When recaptured seven weeks later, the bear had lost 22 percent of her body mass, as well as her cub.

By shedding light on potential mechanisms that facilitated that bear’s survival during her long swim, as well as the overall metabolism and activity of bears, the current study “profoundly contributes to understanding the value of summer habitats used by polar bears in terms of their energetics,” Harlow says. Amstrup adds, “It fills a gap in our otherwise extensive knowledge of polar bear ecology and corroborates previous findings that the key to polar bear conservation is arresting the decline of their sea ice habitat.”

In addition to Whiteman, Ben-David, Harlow and Amstrup, co-authors of theSciencepaper are Research Zoologist George Durner of the USGS Alaska Science Center and Wildlife Biologist Eric Regehr of the USFWS Marine Mammals Management in Alaska, both previously Ph.D. students at UW, who also participated in project development and execution; and Professor Richard Anderson-Sprecher of UW’s Department of Statistics and Research Scientist Shannon Albeke of UW’s Wyoming Geographic Information Science Center, who contributed to data analyses.

Additional support for the project was provided by the UW Program in Ecology and Wyoming NASA Space Grant Consortium. Consultation with key Inuit communities in Alaska and Canada ensured the successful completion of the study.

Source: University of Wyoming. “Polar bears threatened: Experience limited energy savings in summer.” ScienceDaily. ScienceDaily, 16 July 2015

Polar bears threatened: Experience limited energy savings in summer

Hydroelectric dams drastically reduce tropical forest biodiversity

Widely hailed as ‘green’ sources of renewable energy, hydroelectric dams have been built worldwide at an unprecedented scale. But research from the University of East Anglia reveals that these major infrastructure projects are far from environmentally friendly.

A study published today in PLOS ONE reveals the drastic effects of the major Amazonian Balbina Dam on tropical rainforest biodiversity.

The research reveals a loss of mammals, birds and tortoises from the vast majority of islands formed by the creation of the vast Balbina Lake, one of the world’s largest hydroelectric reservoirs.

Lead author Dr Maíra Benchimol, a former PhD student at UEA and now at Universidade Estadual de Santa Cruz, Bahia, Brazil, said: “Hydroelectric dams have been thought to be an environmentally friendly source of renewable power — and in recent years they have been built to supply the burgeoning energy demands of emergent tropical countries.

“Previous studies have shown that large dams result in severe losses in fishery revenues, increases in greenhouse gas emissions, and socioeconomic costs to local communities. Our research adds evidence that forest biodiversity also pays a heavy price when large dams are built.

Prof Carlos Peres, from UEA’s School of Environmental Sciences, said: “Of course, it is widely known that dams cause massive population losses in terrestrial and tree-dwelling species within lowland forest areas that are flooded. However, we’re only beginning to realize the staggering extent of extinctions in forest areas that remain above water as habitat islands.

“The Brazilian government is currently planning to build hundreds of new dams in some of the world’s most biodiverse tropical forest regions. But the high biodiversity costs of mega dams should be carefully weighed against any benefits of hydropower production.”

The Balbina Dam in the Central Brazilian Amazon is one of the world’s largest hydroelectric dams in terms of total flooded area. The creation of this dam saw a formerly unbroken landscape of undisturbed continuous forest converted into an artificial archipelago of 3,546 islands.

The research team carried out intensive biodiversity surveys over two years on 37 islands isolated by the hydroelectric reservoir and three neighbouring continuous forest areas. They also surveyed land and tree dwelling vertebrates at these 40 forest sites.

Further research focused on plants and used high-resolution satellite images to better understand the level of forest degradation on the islands.

Key findings:

– Clear evidence of widespread loss of animals on forest islands following 26 years of isolation, even under the best-case protection scenario ensured by the largest biological reserve in Brazil.

– Large vertebrates including mammals, large gamebirds and tortoises disappeared from most islands formed by the creation of the Balbina Lake.

– Of the 3,546 islands created, only 25 are now likely to harbour at least four fifths of all 35 target species surveyed in the study.

– Island size was the most important factor predicting the number of forest vertebrate species retained.

Dr Benchimol said: “We found that only a few islands larger than 475 hectares still contained a diverse community of animal and bird species, which corresponds to only 0.7 per cent of all islands in the reservoir.”

“In addition to the effects of area reduction, most small islands succumbed to wind exposure and ephemeral fires that occurred during a severe El Niño drought in 1997-98. Post-burn islands retained even fewer wildlife species than islands of similar size that had not been affected by wildfires.”

In another study published last month in Journal of Ecology the authors showed that fires on these small islands have a knock-on effect for animal life, with extinction rates accelerated by the reduction of habitable forest.

Dr Benchimol said: “Different wildlife species respond differently depending on their lifestyles. Those that need small home ranges coped better with forest habitat loss caused by the dam. Nevertheless, the future demographic and genetic viability of small isolated populations in areas affected by major dams seems bleak, as few species are able to maintain gene flow by swimming long distances to reach other islands.”

Prof Peres said: “We predicted an overall local extinction rate of more than 70 per cent of the 124,110 wildlife populations of the species we studied occurring in all 3,546 islands across the entire archipelago. We’re shedding new light into the devastating impacts of large infrastructure projects on tropical forest biodiversity, which should be considered in any Environmental Impact Assessments of new hydroelectric dams.”

‘Widespread forest vertebrate extinctions induced by a mega hydroelectric dam in lowland Amazonia’ is published in the journal PLOS ONE on July 1, 2015.

This research was funded by the Wildlife Conservation Society (WCS), the Natural Environment Research Council (NERC), The Rufford Small Grant Foundation, the Conservation Food and Health Foundation, Idea Wild, the Amazon Region Protected Areas (ARPA) programme, Amazonas Distribuidora de Energia S.A, Associação Comunidade Waimiri Atroari, and the Brazilian Ministry of Education.

Story Source:

The above post is reprinted from materials provided by University of East Anglia. Note: Materials may be edited for content and length.

Journal Reference:

  1. Maíra Benchimol, Carlos A. Peres. Widespread forest vertebrate extinctions induced by a mega hydroelectric dam in lowland Amazonia. PLOS ONE, July 1, 2015 DOI: 10.1371/journal.pone.0129818
Hydroelectric dams drastically reduce tropical forest biodiversity