Increasing polar bear population?

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Abdul Alhazred
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Increasing polar bear population?

Postby Abdul Alhazred » Sun Feb 04, 2007 11:16 pm

OK, it's not a primary source or neutral, but the figures ought to be verifiable.

http://www.charlotte.com/mld/observer/n ... 516171.htm

...

A prime example of its effectiveness came in late December when environmental lobbyists persuaded the Bush administration to recommend that the polar bear be listed as threatened due to global warming.

In lieu of evidence, environmentalists offered mostly anecdotes that polar bears are at risk: isolated reports of a few polar bears drowning in Arctic waters normally containing sea ice as well as a few instances of cannibalism among polar bears.

Then they took a long leap of logic to posit that human-caused global warming will melt most of the ice at the North Pole within 50 years, and that without the ice, polar bears will be unable to hunt seals, their preferred prey.

Fortunately, both for policy and the polar bears, the plight of this one population does not reflect the population trend as a whole. Indeed, since the 1970s, while the world was warming, polar bear numbers increased dramatically from around 5,000 to as many as 25,000 today.

Historically, polar bears have thrived in temperatures even warmer than at present -- during the medieval warm period 1,000 years ago and during the Holocene Climate Optimum between 5,000 and 9,000 years ago.

Polar bears have thrived during warmer climates because they are omnivores just like their cousins the brown and black bears. Though polar bears currently eat seals more than anything else, they also will feast on fish, kelp, caribou, ducks, sea birds, the occasional beluga whale, musk ox and scavenged whale and walrus carcasses.

Mitchell Taylor, a biologist with Nunavut Territorial government in Canada, pointed out in testimony to the U.S. Fish and Wildlife Service that modest warming may be beneficial to bears since it creates better habitat for seals.

...
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Postby Deft One » Mon Feb 05, 2007 5:25 am

He's full of it. For the most part.

See, loss of sea ice habitat will cause a cascading series of impacts on polar bear populations. It is true that seal habitat should improve with loss of sea ice in the short term. Polar bears however will lose a major food source and will have to expend far more energy swimming from ice cap to ice cap. This also means that they will lose some fat storage and that means lower fecundity rates. Bears are known to be adaptable, however given the unprecedented (for bears) rate of climate change predicted and the relatively long generation times, polar bears are at serious risk.

Also consider the tolerance of humans to cohabitation of large omnivores while presenting the possibility of polar bears moving inland and scavenging human remains. And don't even bring up accounts of polar bears being spotted at zoos as evidence that they can live at such and such climate.

The population estimates for the 50's and 60's are just guesses. There were no counts (it was not possible to do then) of polar bear populations, just harvest data. After a treaty in the 70's that controlled polar bear harvest, populations got better, but not by much probably based on monitoring of individual populations. The numbers that we have now are much more accurate, but historical figures are guesses and there are lots out there depending on your bias.

I swear the amount of propoganda and misinformation being spread out there is outrageous. And for what?!
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Postby Abdul Alhazred » Mon Feb 05, 2007 1:29 pm

Thanks.
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Re: Increasing polar bear population?

Postby johannabartley » Thu Nov 22, 2007 5:29 pm

I've heard on this Association that militates to save endangered species just like the polar bears. It's just a rumor now but it is said that in 2008 there will be a big manifestation regarding this problem. Poor polar bears - gentle animals that need our help...

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Re: Increasing polar bear population?

Postby Major Major » Wed Nov 28, 2007 3:23 am

luckily for polar bears they can screw a grizzly and have their genes carried on in the form of a Pizzly Bear!
http://en.wikipedia.org/wiki/Grizzly-polar_bear_hybrid

awwwww....how can anything called a Pizzly be a bad thing?

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Re: Increasing polar bear population?

Postby Deft One » Thu Nov 29, 2007 1:43 am

It would be interesting to know whether or not a Pizzly or a Grolar bear would be reproductively viable. If so, that could spell extra danger for the future of Polar bears. Introgression of unique genetic information would be a major threat if more populations of polar bears are forced south into grizzly territory.
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Re: Increasing polar bear population?

Postby Lance Kennedy » Sat Dec 01, 2007 9:05 pm

In spite of Deft One's assertions, the increase in polar bear numbers is a reality. The reason is that hunting has been drastically cut. In the 1960's heaps of polar bears were shot and their numbers plummeted. Their numbers have been increasing ever since shooting was restricted. The best estimate of current numbers is 22,000.

Will global warming reverse this? Only time will tell for sure. However, the evidence for ice melt causing polar bear mortality is lousy at best. A few bear corpses have been seen floating, and activists jump to conclusions, saying they drowned due to ice melt. It is rather unlikely. Polar bears are superb swimmers. And there are heaps of other possible causes of polar bear mortality in such tiny numbers.

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Re: Increasing polar bear population?

Postby Deft One » Sun Dec 02, 2007 6:14 am

Lance, are you just being contrarian? No one has suggested that polar bears as a whole are drowning to death. However, it is expected that increased distance of swimming to foraging grounds will increase mortality and is just another indicator of increased pressure on this species.

Loss of sea ice poses a danger to polar bears in many other ways. The study linked above (and others) have shown that distributions of polar bear populations are shifting inland, reproductive success is down, morphometric indicators of health like skull size has decreased, and observations of cannibalism are correlated with the recent loss of sea ice.

It has been acknowledged that the hunting ban has at least stabilized the population in a long-term context, but it is only speculation to know if numbers have recovered to any past levels because we dont know them. Satisfactory population data is even impossible to get today, much less ten years ago. However, we know enough about polar bear ecology through monitoring individual populations to have a good idea of the impacts of sea ice loss.

Check this out for the severity of sea ice loss in the Arctic this year. http://earthobservatory.nasa.gov/Newsroom/NewImages/images.php3?img_id=17782

According to the article, at this rate, sea ice could be completely melted by 2030.

So what's the point? There are interested groups that are lobbying to get the polar bear delisted. As we have seen, science does not always play the main factor in policy, especially lately. I am just doing my part (like a good skeptic) to slow the spread of destructive myths.
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Re: Increasing polar bear population?

Postby Deft One » Sun Dec 02, 2007 6:35 am

Here is some reading material. All of these studies support the notion that climate change and sea ice loss pose a considerable risk to polar bears. My search was limited to only the last two years.

Fischbach, A. S., Amstrup, S. C., Douglas, D. 2007. Landward and eastward shift of Alaskan polar bear denning associated with recent sea ice changes. POLAR BIOLOGY 30:11

Richardson, E, Stirling, I, Kochtubajda, B, Richardson, E. 2007. The effects of forest fires on polar bear maternity denning habitat in western Hudson Bay. POLAR BIOLOGY 30:3

Taylor, BL., Martinez, M, Gerrodette, T, Barlow, J, Hrovat, YN. 2007. Lessons from monitoring trends in abundance of marine mammals. MARINE MAMMAL SCIENCE 23:1

Parks, E.K., Derocher, A.E., Lunn, N.J. 2006. Seasonal and annual movement patterns of polar bears on the sea ice of Hudson Bay. CANADIAN JOURNAL OF ZOOLOGY. 84:9

Stirling, I, Parkinson, CL. 2006. Possible effects of climate warming on selected populations of polar bears (Ursus maritimus) in the Canadian Arctic. ARCTIC 59:3

Monnett, C, Gleason, JS. 2006. Observations of mortality associated with extended open-water swimming by polar bears in the Alaskan Beaufort Sea. POLAR BIOLOGY 29:8.

Amstrup, SC., Stirling, I, Smith, TS, Perham, C, Thiemann, GW. 2006. Recent observations of intraspecific predation and cannibalism among polar bears in the southern Beaufort Sea. POLAR BIOLOGY. 29:11

Rosing-Asvid, A. 2006. The influence of climate variability on polar bear (Ursus maritimus) and ringed seal (Pusa hispida) population dynamics. CANADIAN JOURNAL OF ZOOLOGY 84:3.

Thiemann, G, Iverson, SJ, Stirling, I. 2006. Seasonal, sexual and anatomical variability in the adipose tissue of polar bears (Ursus maritimus). JOURNAL OF ZOOLOGY 269:1


To be fair, I found one study that remains skeptical that we can know how climate change might affect polar bear numbers.
Dyck, M. G., Soon, W., Baydack, R. K., Legates, D. R., Baliunas, S., Ball, T. F., Hancock, L. O. 2007. Polar bears of western Hudson Bay and climate change: Are warming spring air temperatures the "ultimate" survival control factor? ECOLOGICAL COMPLEXITY 4:3

Notice the coauthors of Baliunas and Ball. Noteworthy global warming skeptics. Anywho, it was the only source I could find that argues against negative consequences for polar bears regarding the recent turn of events in the Arctic. I tend to go with the consensus.
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Re: Increasing polar bear population?

Postby Lance Kennedy » Sun Dec 02, 2007 8:43 am

To Deft One.

My interest is simply to elucidate that which is scientific. I am not simply trying to be contrarian. The truth is that polar bear numbers are up over previous decades. The speculation is that melting of sea ice may cause them to fall again, but this is currently unproven. It might be true. It might be untrue. Right now, the data is insufficient to permit a definitive conclusion.

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Re: Increasing polar bear population?

Postby Deft One » Sun Dec 02, 2007 3:56 pm

I don't care if it is unproven. In fact, it's nice that it is unproven. However, because we have an insufficient data string (the loss of sea ice at the rates we are witnessing today are only a few years old) to PROVE that polar bears are negatively affected doesn't mean we can't CONCLUDE that they will are based on what we know.

Denialists have made the same argument about global warming, stressing the uncertainty, lack of unanimity between scientists, and wanting to hold off until we have proof. I am tired of scientific "debates" being covered like a religious "debate". There is more here at stake than our personal beliefs, and everyone's opinion is not equally valid. We cannot afford to wait for the proof. Then it is too late.

Besides, Lance, why are you so certain that we have the information to accurately gauge a worldwide number for polar bears yet you feel that we cannot draw conclusions about the impacts of sea ice loss (some of which we have first hand evidence)? What makes you decide whether we know enough?
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Re: Increasing polar bear population?

Postby Lance Kennedy » Sun Dec 02, 2007 6:17 pm

To Deft One.

Re uncertainty.
What we are discussing here is a blend of climatology and ecology. Both are subjects prone to extreme uncertainty, and to error. That is why both resort to statistics to try to quantify the degree of uncertainty involved.

This particular subject is one where there are many unknowns, and many assumptions to be made. For example : How well can a polar bear cope when the ice disappears? We do not know. We know that they are opportunistic and flexible in their food gathering. We know that they are happy to eat a wide range of foods. Can they cope without seals on the sea ice? Probably. Will that lead to a drop in numbers? Probably. But we cannot quantify any of this.

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Re: Increasing polar bear population?

Postby Deft One » Mon Dec 03, 2007 2:33 am

All of your points are valid. It is the response in light of such uncertainty that we may disagree. With all we don't know about the dynamics of regional numbers of bears, the increased presence of humans in the Arctic, and the well-studied bioaccumulation of toxic polycarbons and heavy metals in Arctic predators, the last thing this species needs is the decimation of their primary foraging habitat. It is not ambiguous that this is will have negative implications for the conservation of the polar bear.

It is true we cannot predict the future status of polar bears even if environmental conditions were constant. But that fact should support the necessity for protection, not a delisting as some interests are suggesting.
"I haven't failed, I've found 10,000 ways that don't work." -- Thomas Edison



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