Keyword Tag Sort by


Categories: Climate Ecology Geology Polar Bears

Polar Bear-Climate Connection Supported by New Study

Forecasts of polar bear populations and their likely responses to climate change have been strengthened by a new publication that refutes criticisms of the scientific basis for listing the polar bear under the Endangered Species Act.  

The new paper, by a team of scientists from the U.S. Geological Survey (USGS), Woods Hole Oceanographic Institution (WHOI), University of Alaska, University of Maryland, Canadian Wildlife Service and the US Forest Service, refutes point-by-point a widely publicized critique of polar bear population predictions. The new rebuttal reinforces the reports written by the scientists and accepted by the Department of Interior in its May 2008 decision to list polar bears as a threatened species on the U.S. Endangered Species Act. 

polar bear and her cub

Enlarge Image
To feed themselves and their cubs, polar bears rely on sea ice for platforms to hunt for their main source of food: seals. Largely because of reduced amounts of sea ice, the polar bear is listed as "threatened" under the Endangered Species Act. (Chris Linder, Woods Hole Oceanographic Institution)


“The decision to list the polar bear as threatened was politically charged, and the scientific research on which it was based attracted some criticisms. Our new study shows that the critique is incorrect and based on misconceptions about climate models, the Arctic environment, polar bear biology, and statistical and mathematical methods,” said WHOI biologist Hal Caswell, an author on two of the USGS reports and of the rebuttal.

The rebuttal was published in the journal Interfaces online on April 22, 2009, and will be published in the July-August print edition. The journal recently made the article available for free to the public.

In 2007 when the Department of the Interior was considering listing the polar bear under the Endangered Species Act, it asked the USGS to assemble an international team to analyze information on polar bear populations. The team included Hal Caswell, a mathematical ecologist who specializes in developing population models.

Caswell, along with former WHOI postdoctoral investigator Christine Hunter, and researchers from the USGS and other universities and agencies, developed new models that incorporated USGS-collected information about polar bears’ mortality rates, birth rates, life cycles, and habitats. They coupled these models to projections of Arctic climate changes, especially forecasts of sea ice conditions. They calculated the interplay of all these factors – some 10,000 simulations – to estimate the probabilities of future polar bear population growth or decline. Through their study, Caswell,Hunter, and their colleagues were able to link Arctic sea ice directly to population growth.

Enlarge Image
Mathematical ecologists Hal Caswell of WHOI (above) and Christine Hunter of the University of Alaska developed new population dynamics models that documneted for the first time the critical importance of sea ice for polar bears' survival. (Tom Kleindinst, Woods Hole Oceanographic Institution)


The USGS-led group presented its reports in fall 2007, and in May 2008, the Department of Interior listed the polar bear as a threatened species under the US Endangered Species Act.

Following that listing, a critique of the USGS reports was published in the Sept.-Oct. 2008 issue of Interfaces, a journal that specializes in management and operations research. Its lead author, Scott Armstrong, a professor of marketing at the University of Pennsylvania, is a key architect of a set of principles on the science of forecasting, which are intended to provide guidance on which methods to use under different circumstances. The principles were derived from such fields as economics, finance, management, politics, medicine, and weather.

In performing its “audit” of the USGS reports, Armstrong’s group applied its set of forecasting principles and claimed that nearly 70 percent of them had been contravened by the USGS reports. The authors of the forecasting audit include a physicist and two economists but do not include biologists, oceanographers or climate scientists.

 “We debated writing something short outlining why we don’t think their criticism are valid,” said Caswell. “After going through their report, however, we decided we needed to do a rebuttal of this, and in the end, we went point by point to refute their criticism.”

Caswell continued: “We began by explaining why the sea ice habitat of polar bears is declining and showing how climate models, outputs from which we used as inputs to our analyses, are reliable for forecasting the future climate.  Then we showed how each specific criticism of the Armstrong team was either wrong or misleading.  Finally, we took a look at their principles of forecasting, and found they are too ambiguous and subjective to be used as a reliable basis for auditing scientific investigations.” 

The rebuttal concludes that the audit offers no valid criticism of the USGS conclusion that global warming poses a serious threat to the future welfare of polar bears and that it only serves to distract from reasoned public policy debate.

In the meantime, the USGS continues to collect data in Alaska and Caswell says he will be involved in further analyses of the polar bear populations based on the new data.
 

Related Link: Hal Caswell's Lab, Hal Caswell studies the mathematical ecology of populations and communities.

The Woods Hole Oceanographic Institution is a private, independent organization in Falmouth, Mass., dedicated to marine research, engineering, and higher education. Established in 1930 on a recommendation from the National Academy of Sciences, its primary mission is to understand the oceans and their interaction with the Earth as a whole, and to communicate a basic understanding of the oceans’ role in the changing global environment.

Contact: Media Relations Office, (508) 289-3340, media@whoi.edu

Source: Woods Hole Oceanographic Institution

Related News:

New Antarctic geological timeline aids future sea-level predictions 16 January 2013, 05:31
Radiocarbon dates of tiny fossilised marine animals found in Antarctica’s seabed sediments...

Will changes in climate wipe out mammals in Arctic and sub-Arctic... 14 January 2013, 09:02
The climate changes depicted by climatologists up to the year 2080 will benefit most mammals...

Drought affects Mediterranean truffle harvest 28 November 2012, 02:56
An international research team under the lead of Ulf Büntgen and Simon Egli from the Swiss...

Mythbusting scientists 'undiscover' fantasy island 23 November 2012, 03:54
A team of Australian and international scientists including a geologist from The University of...

Corals Have Evolved Four Lifestyles 1 October 2012, 13:19
A new study by Simon Fraser University researchers will help scientists better understand and...

Ecosystems cope with stress more effectively the greater the... 5 September 2012, 09:09
Ecosystems with a high degree of biodiversity can cope with more stress, such as higher...

Climate more sensitive to carbon dioxide now than in past epochs 7 June 2012, 05:15
Counterexample from the geologic record highlights today's close coupling of climate and...

Cod Has a Key Role in the Whole Baltic Sea 24 April 2012, 03:40
A new investigation put in evidence the key role of cod as regulator of the whole Baltic Sea...

Global Sea Level Likely to Rise as Much as 70 Feet for Future... 19 March 2012, 11:13
Even if humankind manages to limit global warming to 2 degrees C (3.6 degrees F), as the...

Massive volcanoes, meteorite impacts delivered one-two death punch... 17 November 2011, 10:42
A cosmic one-two punch of colossal volcanic eruptions and meteorite strikes likely caused the...