Good news about the polar bear population

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Mon Jan-05-09 02:00 PM
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Good news about the polar bear population

link: http://www.polarbearsinternational.org/ask-the-experts/population/

Ask the Experts: Are Polar Bear Populations Increasing?
Answered by Dr. Andrew Derocher
Some recent media reports have cited inaccurate data concerning polar bears. For clarification on polar bear numbers, we turned to Dr. Andrew Derocher, Chair of the IUCN/SSC Polar Bear Specialist Group.

Dr. Derocher is a polar bear scientist with the University of Alberta in Edmonton, Canada. He also serves on PBI's Scientific Advisory Council.

Question: The U.S. Fish & Wildlife Service has proposed that the polar bear be listed as a threatened species. Yet some news reports state that polar bear numbers are actually increasing. For example, the following paragraph appeared on the Fox News Web site:

"In the 1950s the polar bear population up north was estimated at 5,000. Today it's 20- to 25,000, a number that has either held steady over the last 20 years or has risen slightly. In Canada, the manager of wildlife resources for the Nunavut territory of Canada has found that the population there has increased by 25 percent."

If this is true, then why are scientists worried about population declines?

Answer from Dr. Derocher: The various presentations of biased reporting ignore, or are ignorant of, the different reasons for changes in populations. If I thought that there were more bears now than 50 years ago and a reasonable basis to assume this would not change, then no worries. This is not the case.

The bottom line here is that it is an apples and oranges issue. The early estimates of polar bear abundance are a guess. There is no data at all for the 1950-60s. Nothing but guesses. We are sure the populations were being negatively affected by excess harvest (e.g., aircraft hunting, ship hunting,self-killing guns, traps, and no harvest limits). The harvest levels were huge and growing. The resulting low numbers of bears were due only to excess harvest but, again, it was simply a guess as to the number of bears.

After the signing of the International Agreement on Polar Bears in the 1970s, harvests were controlled and the numbers increased. There is no argument from anyone on this point. Some populations recovered very slowly (e.g., Barents Sea took almost 30 years) but some recovered faster. Some likely never were depressed by hunting that much, but the harvest levels remained too high and the populations subsequently declined. M'Clintock Channel is a good example. The population is currently down by over 60% of historic levels due only to overharvesting. Some populations recovered as harvests were controlled, but have since declined due to climate-related effects (e.g., Western Hudson Bay). In Western Hudson Bay, previously sustainable harvests cannot be maintained as the reproductive and survival rates have declined due to changes in the sea ice.

At this point, we lack quantitative data for an overall assessment of trend in Canada or Nunavut as a whole. There is, however, very strong evidence for a decline in Western Hudson Bay and the Southern Beaufort Sea based on quantitative studies. More recently, scientists working in the Southern Hudson Bay have reported a major decline in the condition of polar bears. A decline in condition was the precursor to the population decline in Western Hudson Bay. There is clear suggestion of a population decline due to over-harvest in Baffin Bay, Kane Basin and possibly Norwegian Bay.

The point is that you cannot simply summarize the status of polar bears—the information lies in the individual populations. You cannot put the various time periods together into a simplistic overview. Sea ice is declining but again, it is not declining the same everywhere. Some small areas of multi-year ice may improve habitat for polar bears. This latter point, however, does not mean that the habitat in all areas will improve and the predictions are very clear that the primary habitat of polar bears is at risk.

We can control harvests through management and these efforts are underway for several of the over-harvested populations. So far, I have not seen any movement on serious consideration of reducing greenhouse gases in North America (or other countries with few exceptions). Climate warming is not under control and I do not see the management changes coming to effect the needed changes in climate change emissions.

Look at the messengers: lobby groups for big business say there is no problem. Yes, conservation groups moved the issue forward for listing under the Endangered Species Act but this was already an issue that was founded on scientific information. The IUCN/SSC Polar Bear Specialist Group was moving on a Vulnerable designation (the same as Threatened under the Endangered Species Act) before anybody heard of actions from environmental groups. Sea ice change and habitat loss is the key driving force. Ignore the bears for a moment and look at the evidence for sea ice change: NASA is a key player in looking at the actual decreases in sea ice. It is an easy matter to put the dots together: no habitat, no seals; no seals, no bears. This never was an issue of polar bears alone. The only effective conservation approach is to protect the habitat and this is an issue of climate change. You can distort the issue any way you so desire. At the end of the day, the sea ice is disappearing. Take away the habitat and the species follows shortly thereafter (or before).

Comparing declines caused by harvest followed by recovery from harvest controls to declines from loss of habitat and climate warming are apples and oranges. Ignorant people write ignorant things.