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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.'” (

At a glance

Ursus maritimus. The Latin name for the world's largest bear hints at its high dependence on the seas around the Arctic. Polar bears are an apex predator that depend on seals for their food. Because of that dependence they mostly live and hunt out on the sea-ice. Excellent swimmers, they are equipped with the means to swim in the frigid Arctic waters. Thick body fat and a heavy, water-repellent coat make such a lifestyle feasible.

Polar bears live in 19 distinct groups around the Arctic. We don't have great data on eight of the groups. Arctic fieldwork is fraught with logistical problems, especially out on the sea-ice. Regarding the other groups, as of 2017, five are regarded as stable. Two are increasing whereas four are declining. Therefore, it's a mixed picture.

The reason why the picture is mixed lies in the four distinct eco-regions making up the Arctic. Let's look at these. Firstly there is the Seasonal Ice Ecoregion off Canada. Here, the ice has always melted in the summer. The bears hunt voraciously before that happens and then go through a seasonal fast on land. Unfortunately, because the ice-melt is beginning earlier and ending later, the fast period is getting longer, causing malnutrition and cub mortality. This bear population is the one that is definitely declining.

Stretching from Alaska to Svalbard is the Divergent Ice Ecoregion. Here, the ocean currents constantly move the sea-ice offshore as it forms. In summer, new ice does not form and a wide gap of open water exists between sea-ice and the land. Offshore, the sea ice is over the depths of the Arctic ocean - an area of relatively low food productivity. The seals remain near land, in the more productive shallows. Again, the problem facing the bears is the increased length of the ice-free season, for the same reasons as above. Bears living in this region are particularly vulnerable.

In the Convergent Ice Ecoregion, from the North Barents Sea around to Eastern Greenland, ice collects along the shore. The bears living in this region therefore have constant access to ice over shallow productive seas. Finally, there is the Archipelago Ecoregion, around the islands of the Canadian Arctic. Here too, the polar bears have been able to remain on the ice all year round. Both Ecoregions are therefore a known or potential stronghold for them.

The primary threat to all of these regions is obviously sea-ice loss due to climate change. As the sea-ice retreats, the bears have to spend more time on land. This can bring them into contact with human populations and such encounters tend not to end well.

Polar bears belong on the sea-ice. The long term trend for sea-ice extent is downward. Even if some populations are stable or even increasing, it's an uneven picture due to the differing characteristics of the regions they inhabit. Rapid Arctic climate change - Arctic Amplification as it's known - is real. Concern for this magnificent creature is entirely justified.

Please use this form to provide feedback about this new "At a glance" section. Read a more technical version below or dig deeper via the tabs above!

Further details

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 on top of climate change, including hunting, pollution and oil extraction. The introduction of snowmobiles, aeroplanes and ice breakers and the increased hunting that followed led to a decline in certain populations.
  • On the other hand, the International Agreement on the Conservation of Polar Bears was introduced in 1973. That restricted or even banned hunting in some circumstances, resulting in a recovery of polar bear numbers.
  • Not all subpopulations are affected to the same degree by climate change. While some subpopulations are well studied, others are data-poor. That means there is insufficient information to make specific statements about current and past numbers.

With this caveat in mind, what do the figures actually say? According to a 2019 report by the World Wildlife Fund, of the 19 recognised subpopulations of polar bears, four are in decline, two are increasing, five are stable and eight don’t have enough data to draw any conclusions (fig. 1).

Population status of polar bears around the Arctic as of 2021

Figure 1: Population status of polar bears around the Arctic as of 2021. Data: Arctic Portal. Map: Wikipedia. Key to eco-regions, clockwise from bottom: EG = East Greenland; DS = Davis Strat; BB = Baffin Bay; KB = Kane Bay; SHB = Southern Hudson Bay; WHB = Western Hudson Bay; FB = Foxe Basin; GB = Gulf of Boothia; QE = Queen Elizabeth; NW = Norwegian Bay; LS = Lancaster Sound; VM = Viscount Melville Sound; MC = M'Clintock Channel; NBS = Northern Beaufort Sea; SBS = Southern Beaufort Sea; CS = Chukchi Sea; LVS = Laptev Sea; KS = Kara Sea; BS = Barents Sea.

Both habitat degradation and over-harvesting are responsible for the decline in some populations. 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. Projections show that this trend will only 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 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. You can read about these habitats, or 'Ecoregions', in the 2021 status report (PDF) issued by the IUCN/SSC Polar Bear Specialist Group. Ecoregions are based on the different ways in which the sea-ice behaves around the Arctic. Current analysis of subpopulations where data is sufficient clearly shows some are in decline, although some areas are too data-deficient to draw a conclusion so far. Further habitat degradation will, however, do nothing but increase the mounting threats to polar bears.

Last updated on 14 January 2024 by John Mason. View Archives

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Comments 26 to 50 out of 68:

  1. Seal populations are through the roof? Why? Seal hunting basically collapsed when the EU banned the import of seal skins. It used to be the Canadians killed thousands of seal pups every year for their white pup fur. Polar Bears aren't the only change. Certain fish populations in the Grand Banks have severely dropped as the seals eat them. Will the Polar Bear populations stay up as the seal population becomes more balanced? Possibly. It will likely end up higher than it was but not at the current extremely elevated levels.
  2. Polar bears may go extinct but probably will not. It's thought that some populations will disappear due to ice loss, but that is currently conflicted based on recent Hudson Bay numbers. Balanced against potential natural losses will be mankind's management: A case could be made that this won't work, or it will result in a polar bear reserve with none elsewhere. But a better case could be made that a high profile species such as polar bears will be relatively easy to manage, but what about the others?
  3. Eric (skeptic) @27, the final fate of polar bears with global warming is a subtle issue. In the absence of humans their fate would be fairly predictable in a warming world. Put simply, polar bears would find refuges on Arctic Island where, free from competition from other top predators, they would be likely to survive even if conditions were debilitating for them physiologically. In contrast on the mainland they would face competition from the northward expanding range of various brown and black bears. We know those brown and black bears are better adapted to survival in forests than are polar bears from the current ranges of the respective species. Those forests will be marching north with time and greater warming, and can be expected to reach the northern shores of North American, Asia and Europe within a few centuries with predicted warming, a situation that would coincide with the extinction of Polar Bears in mainland areas. The polar bears surviving on the islands might also go extinct, simply because their population would be low, and species with low populations can go extinct easily as a result of chance events, ie, a virulent disease, or a number of particularly poor seasons in succession. If the do not go extinct in this way they will reduce in size over a period of thousands of years as do all large species trapped on islands. As a result, the descendants of polar bears would survive as a new species of pygmy polar bears, having probably lost their white coat but not their aquatic adaptions (as the ability to swim between islands would greatly increase range and hence survival prospects). The presence of humans greatly complicates things, first because they already inhabit many of the Arctic islands, and will compete for them more fiercely as the Earth warms, making those islands dubious refuges for polar bears. On the other hand, humans may (and probably will to some extent) intervene to preserve polar bears by creating specific refuges either on islands or on the mainland (by culling brown bears entering the area, and imprisoning poachers etc). Consequently it is impossible to predict categorically that polar bears will go extinct in a warming world. What we can predict that efforts to preserve them will both become more onerous, and in greater conflict with human demands for economic development. Polar bears did survive the Eemian on a Svarlbad without humans (and presumably other islands). But will they be able to do so when Svarlbad's population has increased from it's current three thousand to 30 or more thousand as humans take advantage of the one of the few remaining "temperate" climates in the world?
  4. Tom, thanks for the perspective. Like CO2 and warming the fate of the polar bears lies in policy decisions, although those decisions are much more localized and have clear cut benefits and tradeoffs. Setting aside an island a few centuries from now seems pretty straightforward on one hand and speculative on the other. But the uncertainty will not be scientific, but social structures, policy priorities, etc.
  5. Eric (skeptic) @29, setting aside a single island is unlikely to be sufficient. The space set aside would need to be able to sustain a large ( >> 1000) population of polar bears to maintain genetic diversity. It would need to be able to maintain something like 100 times that number of prey animals. It would need to large coastal extent relative to area because the primary prey animals of polar bears breed in coastal regions and are not able to operate effectively far from water (seals). I suspect that to be sure of polar bear survival other than in zoos you would need to set aside the the entire Canadian Archipelago. I doubt, however, the Canadians or anyone else would be prepared to sacrifice that many resources to preserve the existence of polar bears and NH seals. Despite my suspicion, however, I think the situation is too complex to make any prediction beyond that the survival of polar bears will require a conscious effort by humans, and that the effort required will be substantial in term of economic cost.
  6. I was hoping the document I linked would have some cost estimates but alas it did not. The cost is somewhat speculative but zoos are relatively cheap and feeding a "reserve" area overpopulated with polar bears (somewhat like a large zoo) is an in-between case. If we require strictly natural feeding then costs would be much more substantial and it may be impossible.
  7. Eric (skeptic) @31, the problem with non-natural feeding is that, should we follow BAU, temperatures are expected to be elevated for tens of thousands of years. If we do not let the polar bears gather the majority of their diet, the will become "domesticated" within a few tens of generations. That is, they will loose intelligence, sensual acuity, strength, and probably other essential traits for survival in the wild. That probably doesn't matter so much if they are "returned" to a wild in which there are no comparable top predators. Domestic cats do very well when they go feral in Australia, where the "top predators" are 4 foot long monitor lizards and a variety of very deadly snakes. I believe they become lunch if they go feral in Africa, and "domesticated" polar bears will fair similarly poorly if required to feed themselves in an area with a genuine top predator. That assumes that it will be possible for them to be returned to the wild state, which assumes the large scale survival of a variety of seal species. Again, these can be kept alive in zoos in which case they will loose much of the ability to feed themselves in the wild. Or they can be kept alive in smaller refuges than are required for polar bears (because you do not require as much territory to sustain a large enough population for genetic diversity), but only if they have no predators in which case they will loose their ability to avoid predators within a few generations. I am sure care programs can be implemented that avoid many of these problems. It will not, however, be simple or cheap. As to whether it would be more expensive than providing adequate refuges without supplementary feeding? I could not say.
  8. Eric@27 I wouldn't bet the farm on the most recent survey results from Hudson's Bay if I were you. That survey was done by different people (the government of Nunavut instead of the government of Canada) using different methodologies (aerial survey instead of capture, tag and release) which by themselves could account for the slight increase. I think it is also pertinent to look into the "local knowledge" of the Inuit inhabitants that convinces them that the population isn't declining ... that they are seeing more bears in remote settlements where they had not ranged before. They could be right ... but it also might be that since Hudson's Bay isn't freezing over until November in recent years, and freezes for six weeks less on average, that bears with no natural sources of food who wake from hibernation with hungry cubs start looking for food in places they wouldn't ordinarily go. The more cynical might say that the Nunavut government's decision to raise the polar bear harvest quota last October from eight to twenty-one might have a bearing on it, particularly as hunters from farther south with more money than brains typically pay upwards of $50,000 for the opportunity to do the "harvesting". Best wishes, Mole
  9. Tom, you are right that it isn't simple or cheap: e.g. in the case of Florida panthers "These [studies of rescues prior to Florida panthers] show the benefits of added genetic diversity. The compendium of such direct studies is still so small that it provides scant support for managers justifying expensive rescues.." To their methods I would add artificial insemination to preserve desired traits. Old Mole, I agree that the Inuit have an immediate financial interest in more bears, and there is not enough information to determine what habitat changes have occurred and what those imply for the bears. See for a diverse and thorough survey of Inuit opinion.
  10. TOP @35, the IUCN report says, among other things:
    "Polar bears rely almost entirely on the marine sea ice environment for their survival so that large scale changes in their habitat will impact the population (Derocher et al. 2004). Global climate change posses a substantial threat to the habitat of polar bears. Recent modeling of the trends for sea ice extent, thickness and timing of coverage predicts dramatic reductions in sea ice coverage over the next 50?100 years (Hassol 2004). Sea ice has declined considerably over the past half century. Additional declines of roughly 10?50% of annual sea ice are predicted by 2100. The summer sea ice is projected to decrease by 50?100% during the same period. In addition the quality of the remaining ice will decline. This change may also have a negative effect on the population size (Derocher et al. 2004). The effects of sea ice change are likely to show large differences and variability by geographic location and periods of time, although the long term trends clearly reveal substantial global reductions of the extent of ice coverage in the Arctic and the annual time frames when ice is present."
    (My emphasis, the sentence you quoted is underlined.) Straightforwardly, the sentence immediately preceding the sentence you quoted directly contradicts the conclusion that you wish to draw from the quote. That means whether deliberately or by incompetence you have quoted the report out of context, and in a deceptive manner. You suggest that Polar Bears are a flexible breed, but the report says:
    "While all bear species have shown adaptability in coping with their surroundings and environment, polar bears are highly specialized for life in the Arctic marine environment. Polar bears exhibit low reproductive rates with long generational spans. These factors make facultative adaptation by polar bears to significantly reduced ice coverage scenarios unlikely. Polar bears did adapt to warmer climate periods of the past. Due to their long generation time and the current greater speed of global warming, it seems unlikely that polar bear will be able to adapt to the current warming trend in the Arctic. If climatic trends continue polar bears may become extirpated from most of their range within 100 years."
    (My emphasis) Clearly the report adresses your claim and contradicts it. As counter evidence you provide us nothing more substantive than the infallibility of TOP speaking ex cathedra. Finally, you say that the article says that it is the habitat, not the bears at risk, whereas the report says:
    "There is little doubt that polar bears will have a lesser AOO, EOO and habitat quality in the future. However, no direct relation exists between these measures and the abundance of polar bears. While some have speculated that polar bears might become extinct within 100 years from now, which would indicate a population decrease of >50% in 45 years based on a precautionary approach due to data uncertainty. A more realistic evaluation of the risk involved in the assessment makes it fair to suspect population reduction of >30%."
    (Again my emphasis) A population reduction of greater than 30% in 45 years or less is a clear indication of a population at risk. Therefore in claiming that the article claims it is the habitat, not the bears which are at risk you have straightforwardly misrepresented the article. What is more, the article explicitly categorizes polar bears as "vulnerable", which is defined as meaning:
    "A taxon is Vulnerable when the best available evidence indicates that it meets any of the criteria A to E for Vulnerable (see Section V), and it is therefore considered to be facing a high risk of extinction in the wild."
    (My emphasis) So you have quoted out of context, directly misrepresented the articles contents, and contradicted the article without supporting evidence. Why exactly are we supposed to take anything you say seriously?
  11. @Tom I take it you have read and agree to Section 4 here. I read the article. I pointed out that it is the habitat and not the bears that are at risk according to the article. There were a plethora of possible events that could or are putting them directly at risk and that are currently responsible for their reduced numbers the chief of which is human/bear interaction. The last two assessments of their status flip-flopped which suggests they are borderline vulnerable right now. It would seem that limiting or changing human/bear interactions would have a far greater effect on their current survival. Hunting bears just for the fun of it is just sick.
    Response: [DB] The materiel cited earlier complies to the IUCN policies per these terms.
  12. TOP @36 and DB inline comment, TOP's reference to the terms of use are a deliberate distraction. I will not be distracted - but see below. The important point that TOP is trying to distract from is that he is trying to represent a report that says polar bears are at risk as not saying that polar bears are at risk. Indeed he continues to do so, saying that "it is the habitat and not the bears that are at risk according to the article" (my emphasis). TOP is entitled to form and put forward any view he likes about the risk to polar bears. He is not entitled to misrepresent the opinions of others about that risk, and he is certainly not entitled to put forward those misrepresentations as evidence for his own opinions. As TOP's attention has been drawn to the misrepresentation, and as he persists in it regardless, the only reasonable supposition is that the misrepresentation is deliberate. Lest there be any doubt about this, the article says in its lead section: "Red List Category & Criteria: Vulnerable A3c ver 3.1" Where "Vulnerable" means: "A taxon is Vulnerable when the best available evidence indicates that it meets any of the following criteria (A to E), and it is therefore considered to be facing a high risk of extinction in the wild:"(my emphasis) So the article directly states that polar bears are "facing a high risk of extinction in the wild", which TOP represents as saying that it is "... not the bears that are at risk according to the article." The numbers after the classification indicate that polar bears are facing ...
    "A. Reduction in population size based on any of the following: ... 3. A population size reduction of ≥ 30%, projected or suspected to be met within ... three generations, ..., based on (and specifying) any of (b) to (e) under A1."
    ... where A1 (c) specifies the reason for the risk as ...
    "(c) a decline in area of occupancy, extent of occurrence and/or quality of habitat"
    . So, contrary to TOP, it is habitat degredation, specified as being due to global warming in the article, which is claimed as the reason why the polar bears are facing "a high risk of extinction". The only reasonable conclusion at this point is that TOP is willing to straightforwardly misquote and misrepresent articles as saying the exact opposite of what they do so to further his cause. Everything he says should be understood in that light. Returning to TOP's attempted distraction, I note that terms and conditions do not apply to publicly accessible portions of the website, but only to those sections requiring login. What is more, limited quoting such as I have done constitutes fair use under copyright law, and the resulting product (my post) would constitute a "derivative work" under the terms and conditions even if they did directly apply. If TOP disagrees with my assessment, he is quite welcome to contact the IUCN, and I will modify my comment to comply with their directions. Indeed I would look forward to his doing so, for I would like to see their public comment on TOP's use of the material from their site.
  13. @ Tom
    "TOP's reference to the terms of use are a deliberate distraction."
    Absolutely spot-on. And part-and-parcel of the usual TOP agenda to distort & misinform with due deliberation and intent. Any future comments made by TOP should heretofore be viewed as being suspect until proven otherwise. For his credibility-meter has flatlined. I would submit that it is impossible for a denier to admit to error, as that would be anathema to the denier worldview.
  14. There are four main threats to polar bears in the article. 1) Loss of habitat, sea ice (potential threat) 2) Ingestion of seals rich in pollutants (currently going on) 3) Oil spills (potential threat, but likely to happen in a limited time over a limited area) 4) Harvesting in an unregulated manner (current threat) I would have to ask whether #2 will do them in before #1 or #4? There is not much control over #2.
  15. You might look here for information on what is known to be going on and why.
  16. TOP, if the Arctic is ice-free within 20 years, Nos. 2 and 3 won't really be a factor, because polar bears will begin to seek out new sources of food, and that will bring No. 4 into play. Unless the ice loss flattens for a few years, polar bears are going to have to evolve flippers and a snorkel. DB: if by "denier" you mean someone who has become psychologically invested in maintaining a position, and any threat to that position is seen as a potential attack on confidence or self-esteem (as if SkS were a game board)--ala Doug Cotton. There are plenty of people, though, who post "sciency" unevidenced stuff because they've been misled by opinion-makers; many of those may be called "deniers" but might actually be willing to engage the science and "come unstuck." TOP I have no opinion on--still weighing the evidence.
  17. @DSL I've done some more reading on the subject. #2 is interesting. I found a map showing the PCB levels in polar bears and that highest levels appeared to be around eastern Greenland and the southern part of Hudson Bay. In my opinion the only way PCBs could get up there is by transport in the ocean from farther south (at least the Greenland PCBs). The bears are kind of integrating the PCB content of the water over time which may act like a proxy for long term effects of the currents. #2 and #4 kind of work together some times. It turns out that polar bears aren't real picky as to what they eat and have been killed by eating lead acid batteries/hydraulic fluid and antifreeze. In other words polar bears can be killed/harvested by eating polluted human castoffs/garbage. Until the icepack is gone I would expect the polar bears to go where the food is. Their food is mobile too. So a decline in their population in one area might mean a move to another area where there is more food. If a decline in sea ice means a less extensive feeding ground it might also mean a denser source of food and at least short term an increase in polar bears in particular areas. One thing that a decrease in sea ice might mean is that fishing ships expand into the polar areas previously off limits. That would cut into the polar bear's food's food. I didn't see any mention of that on the IUNC Red List.
  18. "The bears are kind of integrating the PCB content of the water over time which may act like a proxy for long term effects of the currents." By what exotic biological process would that work? Absorbtion through the skin? Bear fur is so dense that water does not even touch the skin, hence their ability to withstand cold water temperatures during long swims. Or do you think bears drink sea water? More plausibly, they absorb the PCBs throug their food, mainly seals or other mammals that concentrate the PCBs because they are near the top of the ocean food web and they have a high fat content where they accumulate a lot of PCBs and other toxins. Where the bears' preys get their food, and the travels of that food are the more interesting questions.
  19. "Polar Bears are in Danger of extinction." What does that mean "in danger?" The cited evidence from the IUCN states that Polar Bears face a risk of a greater than 30% but less than 50% population decline within 100 years. The report specifically states that speculation of their extinction within 100 years is not very realistic.
  20. jzk @44, the report says: 1) That some people have speculated that polar bears will be extinct in 100 years; 2) That extinction in 100 years would "indicate a population decrease of >50% in 45 years; and 3) That a more realistic estimate is a population reduction of >30% in 45 years. At no place does it assert an upper limit on the population loss, so your claimed < 50% is entirely a misunderstanding of the report, just as is your stated 100 year time period rather than the 45 years stated in the report. Fairly straightforwardly, a population that has crashed from about 23,000 to about 15,000 or less in 45 years cannot be expected to miraculously stabilize at that number while the conditions that brought about the collapse continue to worsen. Rather, we can expect it to crash further to about 7,000 or less in the next 45 years, and unless you believe that negative population numbers can be turned around, is plainly heading for extinction at a fast rate. So while extinction by 2150 may be more realistic than extinction by 2100, that is hardly cause for comfort. I would be the first to admit that such a simple calculation does not allow for appropriate nuances. Indeed, I have discussed the relevant nuances extensively above. But those nuances do not justify treating a report which classifies polar bears as "... facing an extremely high risk of extinction in the wild" (definition of vulnerable) can be legitimately interpreted as indicating polar bears are not " danger of extinction". Finally, the report does not "... specifically states that speculation of their extinction within 100 years is not very realistic"! It states that a reduction of >35% in 45 years is a more realistic assessment than a reduction of >50% in 45 years (and hence of extinction in 100 years). But having learnt that African elephants are larger than Indian elephants, we do not conclude that Indian elephants are not very large at all. To do so would be a complete non-sequitor. Claiming your absurd conclusion as a specific statement of the report is a straightforward misrepresentation.
  21. Tom @45, Thanks for the correction on the 45 vs. 100 year fact. Both the report and the SkS article says that there are 20,000 to 25,000 polar bears. Where do you get 15,000 figure? What are the chances that the Polar Bear population crashes to 7,000 within 45 years? Thanks.
  22. @43 Philippe Exactly. That's what the polar bear experts say. Cod --> Seals --> Polar Bear Not sure what the Cod eat yet. Species that ringed seals eat Boreogadus saida and others. This fish feeds on krill and plankton and favors surface feeding and frequents river mouths. [Ref] It is interesting that it survives best at a water temperature of 0-4C. Maybe more than ice loss, a warming of the water above 4C would cause a decline in the food source for polar bears if ringed seals can't adapt to other species. The Russians fish the polar cod commercially so over fishing of Arctic water with more ice free days could impact polar bears.
  23. jzk @46, in round figures, the difference mean of 20 and 25 thousand bears is 23 thousand. Less a third (8 thousand) leaves you with 15 thousand in 45 years. A further 45 years on (2100) leaves you with 7 thousand. A further 45 years on leaves you with no bears in the wild. If the IUCN projection is correct, absent a radical improvement of conditions for the better the IUCN prognosis is not of a surviving population, but on one going extinct, but more realistically, after 2100 rather than before it.
  24. The figures that seemed more concerning to me, that were quoted by Dr Amstrup here, were the yearling survival rates of 6% in the Hudson Bay population whereas other populations are 22%. It sounds to me like there would eventually be a critical point where polar bear populations would collapse. If the bears can't sufficiently replenish their numbers then you're stuck with a collapse within ~one generation. So, that begs the question, what are the factors that impact yearling survival rates? Because that's what will do them in. If seasonal ice-free conditions have the greatest impact on yearlings, that might be the weak link critical to their survival.
  25. Speaking of polar bears, here are a couple of interesting facts about where they came from and where they may be headed. “Polar bears have maternal Irish brown bear ancestors” by Stephen McKenzie, BBC News, Jul 7, 2011 “Brown and polar bears set to mate again due to global warming” by Cathy Hayes, Irish Central, Jul 13, 2011

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