Arguments
How will global warming affect polar bears?
The skeptic argument...
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)
What the science says...
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.
Last updated on 30 September 2010 by Anne-Marie Blackburn.
"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/ -
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
No seals? Where's the outcry for that? Where's their endangered status? I guess they're not as cute as polar bears.
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."
is it your speculation that the cause of the projected population reduction is hunting? In the link you provide there's nothing about it.
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.
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").
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.
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
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.
[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.
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?
( -Snip- )
[DB] Moderation complaints snipped.
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.
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
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.
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
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. :]
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.
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?
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?
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.
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.
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
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 http://www.researchandpractice.com/articles/2-2/dowsley-1.pdf for a diverse and thorough survey of Inuit opinion.
(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:
(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:
(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:
(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?
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.
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 ...
... where A1 (c) specifies the reason for the risk as ...
.
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.
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.
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.
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.
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.
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.
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.
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 "...in 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.
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.
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.
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.
“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