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How will global warming affect polar bears?

What the science says...

Polar bears are in danger of extinction as well as many other species.

Climate Myth...

Polar bear numbers are increasing

“A leading Canadian authority on polar bears, Mitch Taylor, said: ‘We’re seeing an increase in bears that’s really unprecedented, and in places where we’re seeing a decrease in the population it’s from hunting, not from climate change.'” (Scotsman.com)

Polar bears are found in the Arctic circle and surrounding land masses. There are 19 recognised subpopulations, and estimates place their numbers at about 20,000 to 25,000. Polar bears are classed as vulnerable by the World Conservation Union (IUCN) and listed as a threatened species under the US Endangered Species Act. Yet some claim that polar bear numbers have increased since the 1950s and are now stable. So what is the situation for this species?

First of all, a few points need to be made about polar bear numbers:

  • Nobody really knows how many bears there were in the 1950s and 1960s. Estimates then were based on anecdotal evidence provided by hunters or explorers and not by scientific surveys.
  • Polar bears are affected by several factors, including hunting, pollution and oil extraction. Most notably, hunting, particularly following the introduction of snowmobiles, airplanes and ice breakers, led to a huge decline in certain subpopulations. The introduction of the International Agreement on the Conservation of Polar Bears in 1973, which restricted or even banned hunting in some circumstances, consequently resulted in an increase in polar bear numbers.
  • Not all subpopulations are affected to the same degree by climate change, and while some subpopulations are well studied, for others there is insufficient data to make broad statements about current and past numbers.

With this caveat in mind, what do the figures actually say? According to a 2009 report by the IUCN Polar Bear Specialist Group, of the 19 recognised subpopulations of polar bears, 8 are in decline, 1 is increasing, 3 are stable and 7 don’t have enough data to draw any conclusions. Figure 1 below compares the data for 2005 and 2009.

 

Figure 1: Subpopulation status of polar bears for 2005 and 2009 (Source: Polar Bear Specialist Group)

Both habitat degradation and over-harvesting are responsible for the decline in some subpopulations. To understand why the IUCN and US Endangered Species Act consider polar bears to be at risk, it is important to look at how rising temperatures are likely to affect their habitat in the future. Polar bears are highly specialised mammals which rely heavily on sea ice for food and other aspects of their life cycle. Satellite data show that Arctic sea ice has been decreasing for the past 30 years, and projections show that this trend will continue as temperatures carry on rising. The changes in sea ice affect polar bears in several ways:

  • The early retreat of summer sea ice means that bears have less time to hunt and therefore less time to build up fat reserves.
  • The fragmentation and reduction in sea ice has several impacts. It forces the bears to swim longer distances, using up some of their fat reserves. It also reduces the number of seals, which are the bears’ main source of food, and impedes travelling and den making. And it also forces the bears to spend more time on land, with increased interactions with humans potentially leading to higher mortality.

To get an idea of the potential impacts of future climate change on polar bears, we can look at subpopulations found at the bears’ southern range, where habitat changes have been most noticeable so far. A good example is the western Hudson Bay subpopulation, which is one of the best studied. Here, ice floe break-up is taking place earlier than 30 years ago, effectively reducing the feeding period by about three weeks. As a result, the average weight of female polar bears has dropped by about 21% between 1980 and 2004, and the population declined by 22% between 1987 and 2004. In Alaska, there is evidence of increased cub mortality caused by a decline in sea ice.

In conclusion, the reason polar bears have been classed as threatened comes from the impacts of future climate change on the bears’ habitat. Current analysis of subpopulations where data is sufficient clearly shows that those subpopulations are mainly in decline. Further habitat degradation will increase the threats to polar bears.

Basic rebuttal written by Anne-Marie Blackburn


Update July 2015:

Here is a related lecture-video from Denial101x - Making Sense of Climate Science Denial

 A further website of interest is from WWF.

Last updated on 22 July 2017 by pattimer. View Archives

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Comments 1 to 25 out of 76:

  1. See Cold Beer Please post in the Artic Ice thread: "Beginning in early January 2009, sensor drift caused an underestimation of ice that grew until the error was finally caught in the mid-February. Internet visitors who look to the NSIDC for data sent emails to the center and, it became clear that there was a significant problem—sea-ice-covered regions were showing up as open ocean. (See NSIDC)" From NCPA: "Though polar bears are uniquely adapted to the Arctic region, they are not wedded solely to its coldest parts nor are they restricted to a specific Arctic diet. Aside from a variety of seals, they eat fish, kelp, caribou, ducks, sea birds and scavenged whale and walrus carcasses. In addition, as discussed above, Arctic air temperatures were as high as present temperatures in the 1930s and polar bears survived. Interestingly, the World Wildlife Fund (WWF), an international organization that has worked for 50 years to protect endangered species, has also written on the threats posed to polar bears from global warming. However, their own research seems to undermine their fears. According to the WWF, about 20 distinct polar bear populations exist, accounting for approximately 22,000 polar bears worldwide. As the figure shows, population patterns do not show a temperature-linked decline: Only two of the distinct population groups, accounting for about 16.4 percent of the total population, are decreasing. Ten populations, approximately 45.4 percent of the total number, are stable. Another two populations - about 13.6 percent of the total number of polar bears - are increasing. The status of the remaining six populations (whether they are stable, increasing or decreasing in size) is unknown. Moreover, when the WWF report is compared with the Arctic air temperature trend studies discussed earlier, there is a strong positive (instead of negative) correlation between air temperature and polar bear populations. Polar bear populations are declining in regions (like Baffin Bay) that have experienced a decrease in air temperature, while areas where polar bear populations are increasing (near the Bering Strait and the Chukchi Sea) are associated with increasing air temperatures. Thus it is difficult to argue that rising air temperatures will necessarily and directly lead to a decrease in polar bear populations." www.ncpa.org/pub/ba551/ -
  2. UNPRECEDENTED LOSS OF SEA ICE RENEW CONCERNS FOR SURVIVAL OF THE WORLD'S POLAR BEARS July6,2009(Copenhagen,Denmark) At the 15th meeting of the IUCN Polar Bear Specialist Group...renewed the conclusions from previous meetings that the greatest challenge to the conservation of polar bears is ecological change in the Arctic, resulting from global warming. "The Western Hudson Bay subpopulation has been on the declilne for almost two decades...the body condition in polar bears is linked to the availibility of sea ice and time of spring break-up; and that when sea ice is available for less time, body condition declines ultimately affecting reproduction in adult female bears..."... ...Reviewing the latest information available, the PBSG concluded that one of 19 subpopulations is currently increasing, three are stable and eight are declining. For the remaining seven subpopulations, available data were insufficielnt to provide an assesment of current trend. The subpopulation increasing is located in Canada's high Arctic, an area that has not seen as much loss of sea ice as others, suppporting the Group's analysis of the critical relationship between the health of polar bears and the amount of sea ice... The IUCN (International Union for the Conservation of Nature and Natural Resouces) Polar Bear Specialist Group...each of the five circumpolar nations that signed the International Agreement for the Conservation of Polar Bears of 1973 - Canada, USA, Greenland(Denmark), Finland and Russia... polarbearsinternational.org Press Release ...(Nov3,2009): For the first time, researchers are studying...the summering ecology of polar bears of the southern Beaufort Sea who choose to migrate north to the sea ice of the polar basin when the winter ice pack melts, rather than return to the shores of Alaska... ...ice breaker expedition... ..."Polar bears need appropriate ice to hunt and survive. Young, thin ice can break up or disappear in a storm and older ice can actually be too thick for the bears to hunt seals..."... Polar Bears International
  3. "No sea ice means no seals which means no polar bears." No seals? Where's the outcry for that? Where's their endangered status? I guess they're not as cute as polar bears.
  4. jasonblanchard, at least one species of seal is indeed at risk. But, controversially, the U.S. recently denied a request to list them as endangered.
  5. The Norwegian polar bear study group shows polar bear populations declining in 8 areas: http://pbsg.npolar.no/en/status/status-table.html but obfuscates the fact that they are declining because they are hunted. Also their estimates have been challenged by indigenous groups interested in hunting. (e.g. nunavut_government_reduces_baffin_bay_polar_bear_quota/) A more accurate phrasing would be "What the science says: polar bear populations are declining primarily due to overhunting. Their long term survival is at greater risk from declining sea ice."
    Response: [RH] Fixing links that are breaking page format.
  6. The real current problem for polar bears http://www.bearskin-rugs.com/polar-bear-rugs-c-62.html is that they are worth $8000 dead.
  7. Eric, is it your speculation that the cause of the projected population reduction is hunting? In the link you provide there's nothing about it.
  8. Riccardo, the Norwegian group doesn't use the word hunting, only the word "removal" which is an obfuscation. The Baffin Bay population with 2000 bears has a hunting quota of about 100, but in fact about 200 have been hunted each year. But the indigenous groups maintain that the population is both underestimated and replenished by polar bears migrating from neighboring areas.
  9. I would add this item about the bears. We stopped shooting the crap out of them in 1973 due to a treaty.
  10. Eric, actually they use "removal" and "harvest"... if you really think that is "obfuscation" then I'd say you place entirely too much weight on semantics. In any case, the claim that hunting is the most significant problem are simply insupportable from the data. Even setting aside the fact hunting quotas can be (and ARE) adjusted as their impact is determined and thus have no long term significance... the majority of population decline is attributed to sea ice loss. For example, the large Davis strait sub-population has an estimate of sustainable kills per year of 66 bears... and 60 bears average actually taken over the past 5 years. Yet the population is in decline, because sea ice conditions have deteriorated. Ditto for the Southern Beaufort sea and Western Hudson Bay groups. Likewise Southern Hudson Bay is currently stable, but the bears have begun to lose body mass due to loss of sea ice (just as observed in other areas prior to population declines) and thus are projected to decline in the future. Over hunting is a temporary problem correctable by adjusting quotas (which is done all the time) and which is only impacting a small percentage of bears. Sea ice loss is a long term problem with no known solution that is threatening several of the largest sub-populations with being wiped out entirely.
  11. All of the above arguments seem to be well researched and effectively made. However, can anyone truly hold stance on a certain side of this argument unless they have actually experienced and seen the possible increasing or decreasing numbers of polar bears? And the statement of "no sea ice means no seals which means no polar bears" seems to be logical. Yet doesn't this statement contain a fallacy of composition? I see it unfit to make such a series of conclusions so cut and dry. There must be many other factors that affect the population of the Polar bears and to limit there existence to a dependence upon just one of those seems to me to be slightly frivolous. I hope I didn't offend anyone, I was simply offering my view upon the arguments thus given.
  12. CBDunkerson (#10), thanks for answering on this old thread. The study group says that the Davis Strait population has grown over the past 30 years (as have most populations), that the growth rate is now just under the replacement rate without considering hunting and that along with hunting the decline is due to "short-term and local density dependence, stabilization of harp seal (Pagophilus groenlandicus) numbers and declining ice conditions" Ice is the 800 pound gorilla knocking at the front door and is all the lead article in this thread talks about. Nothing about the elephant in the living room. You say it is "correctable" but have you asked the Inuit who get income (up to $20k) from selling the tags even if a bear is not killed as a result? Hunting impacts a huge percentage of bears, up to 10% of some populations, I don't see how you can say it is small. In any case, I fail to see how the general public is served by leaving out that important context (along with the local "density dependence" also known as "too many bears in one area").
  13. Eric, the article above references a USGS study from 2006 which looked at only a few regions and specifically at habitat loss. These were sufficient to disprove the false claim that 'polar bear numbers are decreasing'. Adding in information about hunting would be irrelevant to the issue of climate change and misleading given that hunting losses can be recovered IF the habitat can support more bears. As to 'density dependence'... bears go where the food is. When there's no ice in some regions you're naturally going to get bears relocating towards areas that DO have ice. Until recently that included the Davis Strait region. So now you've got alot of bears there and not enough food for them... but even less food back in the areas they came from. The whole 'the population has grown over the past 30 years' bit is also a red herring because 30 years ago polar bears were on the brink of extinction due to there having been no hunting controls at all. The fact that numbers recovered so quickly once hunting limits were put in place shows that hunting is a manageable issue. Loss of habitat is not. As the available food supply dwindles so does the total number of bears. That is an inevitable and obvious dynamic.
  14. Heh, that should have been 'polar bear numbers are INcreasing' in the second sentence of the post above. Oi!
  15. a broader context: Ecol Appl. 2008 Mar;18(2 Suppl):S97-125. Quantifying the sensitivity of Arctic marine mammals to climate-induced habitat change. doi:10.1890/06-0546.1 http://www.esajournals.org/doi/abs/10.1890/06-0546.1
  16. Thanks very much for the update (30 September 2010) on this older post. I just noticed it now and it is much improved in context over the original.
  17. Four bears found in the sea, presumably drowned. Worldwide attention and focus on potential risk of climate change to polar bears. Thousands killed by hunting legally or illegally killed over the last 3 years. A painful silence ensues. Do I smell the scent of double standards and hypocrisy? I’m pleased to see this posting had the honesty to point out the hunting issue. While we may not be able to conclusively show a bear died from shrinking sea ice, a bullet in the head is pretty conclusive.
    Response:

    [DB] "double standards" "hypocrisy" "honesty"

    Your ideology is showing; such talk has no place at SkS.  If you cannot construct a comment based upon the science...then don't make the comment.

  18. Garethman: "Do I smell the scent of double standards and hypocrisy?" No, I'm afraid you're smelling something else there. Can polar bear numbers decrease due to hunting? Why yes... yes they can. Until the 1960s there were no restrictions on hunting polar bears and the population dwindled to just a few thousand bears. They were on the brink of extinction. Can polar bear losses due to hunting be reversed? Again, yes... yes they can. When hunting limits were put in place the polar bear population exploded (~500% growth) over the next 30 years. From these things we can see that allowing hunting can decrease polar bear numbers and restricting hunting can increase them. There are laws and ongoing monitoring in place to determine whether hunting is decreasing polar bear populations and to adjust quotas accordingly. Ergo, hunting does not seem to be a long term threat to polar bear survival. Now, let's look at habitat loss. If the area where the bears hunt and den gets smaller can polar bear numbers decrease? Yes... less area for polar bears equals less polar bears. Indeed, polar bear numbers are now decreasing in many areas where hunting has not increased... but sea ice has retreated. Do we have laws and monitoring in place to reverse habitat loss when it causes polar bear numbers to decrease? No. So... regulated hunting is not a threat to polar bear survival... while unregulated habitat destruction is. Gee, which issue is it hypocritical to focus on?
  19. I agree with you CB on the habitat loss issue, we should not stand by and let it happen. But I also cannot stand idly by while thousands of bears are shot by “sportsmen” If the population exploded after unlicensed unregulated hunting stopped, we see how hunting can effect a species. Maybe licensed hunting does not impact as much as unlicensed, but it has not preserved fish stocks in Europe and I don’t see why bears will be any different in the long run. If they are endangered, they don’t need the extra pressures on their population. For me, (and this I know is more personal than referenced), it does not make sense to talk about a threatened species, and support hunting it at a high level at the same time. ( -Snip- )
    Response:

    [DB] Moderation complaints snipped.

  20. garethman wrote: "But I also cannot stand idly by while thousands of bears are shot by “sportsmen”" According to the IUCN polar bear specialist group, fewer than a thousand bears on average have been killed by hunting over each of the past five years. That includes somewhere between 100 and 200 killed in the Chukchi sea area (where Russia does not enforce quotas). This works out to about 4% of the population per year. Under those kind of controls the population grew steadily for decades before leveling off and then starting to decline over the past twenty years, primarily due to sea ice loss. It is noteworthy that during the peak of unregulated hunting the number of bears killed each year was 'only' about 1500. As the population declined (and it became harder to find bears to kill) that dropped down to about 1000 per year. Given that there were only about 5000 left when hunting limits were put in place it is clear how dire the situation was. Yet just a slight reduction in the number killed each year allowed the population to rapidly increase. Yes, as habitat loss puts increasing stress on the ability of polar bears to survive, maintaining the hunting levels of the recent past would further compound the problem... but it seems unlikely that is going to happen. Both the United States and Canada have already established new protections for the bears and are evaluating further changes. In any case, on its own regulated hunting is clearly not a problem. As the population decreases so do the quotas. Sea ice loss, on the other hand, is increasing in severity. Yet, those 'skeptics' who have moved on from the 'polar bear numbers are increasing' lie all seem to focus on hunting as the new way to avoid even thinking about the real problem. All polar bear hunting could be banned (it very well may be within the next twenty years) and the total polar bear population would still decrease if nothing is done about sea ice loss.
  21. CB, Other studies have found that polar bear populations are largely affected by hunting and seal populations. http://repository.upenn.edu/cgi/viewcontent.cgi?article=1145&context=marketing_papers&sei-redir=1#search=%22polar%20bear%20seal%20population%20increase%22
    Response: [Dikran Marsupial] Link activated. Is this article peer-reviewed? It appears to be published in a social sciences journal of some kind. Do you think a social sciences journal is likely to be able to give a competent peer review to a paper on polar bear populations? Do any of the authors have expertise in polar bears (one is an astrophysicist and the other two are in marketing). Are they in a good position to judge whether they have correctly intepreted the previous studies on polar bears?
  22. "Do you think a social sciences journal is likely to be able to give a competent peer review to a paper on polar bear populations?" There's that and the fact there isn't a polar bear specialist among the three authors. 2 are in marketing/economic forecasting. The other is Willie Soon.
  23. Arghh, Dikran Marsupial added to the mod response and stole my thunder! lol
    Response: [Dikran Marsupial] Ooops, sorry!
  24. 21, Eric the Red, You post comments and links, but you didn't bother to actually follow the link I already gave you which rebuts that particular "study" (which is actually an audit on the quality of the studies used in "....nine government reports were written to help U.S. Fish and Wildlife Service managers decide whether or not to list polar bears as a threatened species." Rebuttal of “Polar Bear Population Forecasts: A Public-Policy Forecasting Audit” In particular, this study by actual scientists in the field of study found that the study you linked to was "mistaken or misleading on every claim." The "qualified scientists" who authored your paper are: J. Scott Armstrong, Professor of Marketing, The Wharton School, University of Pennsylvania Kesten C. Green Business and Economic Forecasting Willie Soon, Astrophysicist, Harvard-Smithsonian Center for Astrophysics
  25. Oh look! Willie Soon... so this goes right back to the 'climate skeptics and their myths' thread. :] Setting that aside, the statement that polar bear numbers are impacted by seal populations is amusing... considering that seal populations are also declining due to global warming; Global warming -> sea ice melts earlier in the year -> seal dens on the ice melt away -> seal pups drown -> fewer seals -> fewer polar bears. So again, 'polar bear numbers are not declining due to global warming'... they're declining due to things CAUSED by global warming. :]

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