Are Polar Bears Really an Endangered Species?
Tuesday, May 13, 2008
The Bush administration must decide by Thursday. Its answer may have serious consequences for the U.S. energy economy.
Environmentalists use charismatic megafauna to raise awareness of and promote policy solutions to perceived environmental threats. Studies show charismatic species are more likely to be protected than are less photogenic animals. Giant pandas are charismatic megafauna, as are whales, salmon, eagles, and caribou. The latest example is Ursus maritimus, the polar bear.
Environmental groups, claiming manmade global warming threatens the polar bears’ survival, have called for an endangered species listing with extraordinarily far-reaching consequences. Such a listing would most likely place the Arctic region off limits for mineral exploration, and would very likely lead to strict federal regulation of greenhouse gas emissions. As of this writing, the Bush administration has not rendered a verdict on whether polar bears will be declared an endangered species, but a federal judge has given the administration a deadline of May 15 (this Thursday) to make a final determination.
As Carl Sagan observed, “Extraordinary claims require extraordinary evidence.” This should be especially true when the stakes are significant and are likely to impose considerable costs or limitations on economic development.
How Many Polar Bears Are There?
Polar bears are difficult to study for a variety of reasons. They live in isolated and inhospitable parts of the Arctic; their home range often exceeds 200,000 square kilometers; and the Arctic is such a hostile environment that polar bears can only be counted at certain times of year and in areas close to landmasses.
Since they can’t accurately count either polar bears or their offspring over time, scientists make population estimates based on limited data. There are two main ways to count polar bears: through periodic flyovers of suspected habitat or by capturing and marking a subpopulation of bears and then using the frequency of recapture as a means to estimate the size of a population. Few subpopulations have been surveyed repeatedly, and the surveys that exist were taken over different years, with some dating back to the 1980s. Where even that data is unavailable, population estimates are created from hearsay: local people report seeing a certain number of polar bears to researchers, who then estimate the size of the population that would be needed to support such a number of sightings.
Data on polar bear populations are relatively scarce; data on population trends are nearly nonexistent.
Given these uncertainties, the best estimate published by the International Union for Conservation of Nature’s Polar Bear Specialist Group is that there are about 20,000 to 25,000 polar bears worldwide. The bears are spread out around the Arctic in 19 separate subpopulations that researchers think are largely non-interbreeding. The groups range in size from small groups of several hundred bears to a few larger groups of several thousand.
While data on polar bear populations are relatively scarce, data on population trends are nearly nonexistent. So trends in population are predicted using something called population viability analysis (PVA), which is a kind of statistical modeling. Like other statistical models, PVA can be a useful tool, but its results are only as accurate as the data and the model assumptions that go into it. According to PVA experts, to predict extinction or other outcomes requires that you have between five and ten times as many years of good historical data. In other words, if you want to predict ten years out, you would need 50 to 100 years’ worth of historical data.
The highest quality data on polar bear populations simply won't do the job. According to the Polar Bear Specialist Group, there is sufficient historical aerial and mark/recapture data to predict population trends for 12 of the 19 subpopulations. Of these, five are estimated to be in decline. Still, only two of these five include data collected after 1998.
Are Polar Bears Threatened By Climate Change?
As with most everything involving climate change, data are limited and studies are contradictory. Satellite imaging has only allowed accurate measurement from about 1979—a short span of time to use in extrapolating forward. The Intergovernmental Panel on Climate Change (IPCC) summarizes Arctic ice changes in its most recent report: “Satellite data indicate a continuation of the 2.7 ± 0.6% per decade decline in annual mean Arctic sea ice extent since 1978. The decline for summer extent is larger than for winter, with the summer minimum declining at a rate of 7.4 ± 2.4% per decade since 1979. Other data indicate that the summer decline began around 1970.”
The IPCC computer models project that Arctic ice decline will continue into the future. But the IPCC projections are based on the assumption that Arctic ice melting is the result of global warming caused by greenhouse gas emissions, and that remains a questionable assumption. In a January 2008 publication in Nature (hardly a hotbed of climate change skepticism), Nordic researchers took a look at the vertical distribution of atmospheric heating. They found that Arctic heating has actually been happening too high in the atmosphere to reflect greenhouse gas causation. What the data seem to indicate is that heat from the tropics is being transported to the Arctic by wind patterns that are not well understood. Thus, at present, we cannot assume that the IPCC predictions for Arctic ice melt trends are meaningful. Recently observed Arctic melting could very well be a short-term phenomenon unrelated to manmade global warming.
Polar bears survived an interglacial period when temperatures were considerably warmer than they are at present.
At present, polar bear populations are robust and, according to native peoples living in the Arctic, are considerably larger than they were in previous decades. Predictions of polar bear endangerment are based on two sets of computer models: one set predicts how much Arctic sea ice will melt as a result of global warming, and the other predicts how polar bear populations will respond. But computer models of climate change are known to be fraught with problems, and the ecological models used to predict polar bears’ response to climate shifts are equally limited.
It is essentially impossible to know whether polar bears are endangered and whether their habitat is threatened by manmade global warming or other natural climate cycles. What we do know about polar bears is that, contrary to media portrayals, they are not fragile, “canary in the coal mine” animals, but are robust creatures that have survived past periods of extensive deglaciation. Polar bear fossils have been dated to over 100,000 years ago, which means that polar bears have already survived an interglacial period when temperatures were considerably warmer than they are at present and when, quite probably, levels of summertime Arctic sea ice were correspondingly low.
If polar bears are placed on the endangered species list, the legal hurdles to oil and gas drilling will increase. Last year, Shell Offshore Inc. was about to start drilling in the Beaufort Sea when a court order halted the activity on the grounds that the federal government did not thoroughly assess the environmental impact before granting Shell permission to drill. In petitioning against the drilling, environmental groups invoked sea ducks, whales, and, of course, polar bears, as well as the effect that drilling could have on native populations. The U.S. Minerals Management Service estimates that the area holds the potential for 7 billion barrels of recoverable oil and 32 trillion cubic feet of recoverable natural gas.
As we have seen, there is no “extraordinary evidence” that polar bears are threatened by manmade global warming. But is the mixed evidence sufficient to justify setting aside Arctic development and regulating our energy economy for the sake of the animal? The Bush administration must give its answer by Thursday.
Image by Darren Wamboldt/The Bergman Group.