What
has been happening to polar bears in recent decades?
Scott L. Schliebe
Polar Bear Project Leader
U.S. Fish and Wildlife Service/MMM
Anchorage, AK
Polar Bear Ongoings
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Polar bear photograph
provided by Cold Regions Research and Engineering Laboratory |
Polar bears have long captured the attention of the
general public but probably at no time in the past have they been
more in the forefront of the public's imagination than today. Today's
heightened interest in polar bears may be due in part to an enhanced
understanding of the ecology of polar bears, their environment,
and an increased interest in Arctic issues brought on by concerns
for climate change. Results of years of research and studies are
now available to an interested public, and efforts to communicate
this information to the public has been more effective in recent
years than in the past. As a result the current public is generally
well-informed and educated regarding the ecology of polar bears.
This public, unlike previous publics, has a variety of communication
tools that enable it to interact and communicate more effectively
with researchers and managers.
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Polar bear distribution |
What have we learned? We now know that polar bears
are not a single large homogeneous population that roams throughout
the Arctic. Instead groups of polar bears referred to as stocks
or populations, are distributed throughout the Arctic. Research
begun in the late 1960s and continuing today also provides a thorough
backdrop of information on population demographics, systematically
analyzed data on population boundaries, population movements, population
size, reproductive and survival parameters, and other useful information
about biological, physiological, and ecological aspects of polar
bears.
We also realize that polar bears do not occur in large
numbers; their ability to replace individuals in the population
is very limited and population growth is extremely slow; they are
long-lived creatures, which helps to offset the low reproductive
potential; their populations fluctuate in response to natural factors
such as climate and prey availability; and, populations can also
be impacted by humans through factors such as hunting, oil spills,
shipping, and other activities. We also realize that the level of
human presence and activity in the Arctic continues to build. As
a result the potential for humans to impact polar bears has never
been greater than today.
Technologically, researchers have been blessed in the
last 30 years. Advances in satellite telemetry allowed researchers
to follow individual bears over time and greatly enhanced our knowledge
of movements and population bounds. Infrared thermal sensory equipment
is providing promise in detecting polar bear dens beneath the snow.
Extended time-series of data now available for some populations
documents trends that were previously not apparent. Improvements
in aircraft and vessel transportation have provided access to a
larger portion of the range of polar bears than was previously accessible.
Finally, technologic advances have allowed for multi-disciplinary
Arctic research, which is in many cases supported by polar-class
icebreakers. All of these advances plus greater understanding of
population dynamics and population modeling now allow for greater
precision in making management decisions and a better understanding
of risks and consequences of management actions.
In the past, one of the greatest saving graces for
polar bear populations was the fact that their habitat was relatively
pristine and secure from alteration. In fact a very large portion
of the high arctic was void of any human presence. Hence at that
time the greatest concern for polar bear populations were over harvest
and human development that was occurring at the fringes of the range
of polar bears.
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Changes in sea ice
extent
over the past 25 years |
Polar bears and their prey have evolved to living in
the extreme conditions of the Arctic. Polar bears and seals are
dependent on sea-ice for foraging, resting, and reproduction. The
Arctic ecosystem was shaped by climate and continues to be driven
today by climate. Polar bears and ice seals, primarily ringed seals,
serve as key indicators of the effects of climate change on the
Arctic environment. Today, polar bear populations are facing threats
previously unprecedented during recorded history in the Arctic.
Recent climate change scenarios based upon modeling of climate trend
data predict that the Arctic region will experience major changes
in the upcoming decades. On the most drastic end of the spectrum
one model predicts that the Arctic basin may be void of ice within
50 years. Other models have shown that ice thickness has decreased
by 40% during the past 30 years and the average annual extent of
ice coverage in the polar region has diminished substantially, with
an average annual reduction of over 1 million square kilometers.
While the ultimate or progressively evolving effects
of climatic change on polar bear populations is not certain, we do
recognize that even minor climate changes could likely have a profound
effect on polar bears. The following is from the IUCN/Species Survival
Commission, Polar Bear Specialist Group (PBSG) web site and in summary
indicates the following:
- Climate changes on prey species will have
a negative effect on polar bears
- increased snow can result in reduced success in successfully
entering seal birth lairs
- decreased snow or increased seasonal rain patterns could
effect seal pupping by not providing adequate snow for construction
of birth lairs or if rain fall by collapsing birth lairs thus
reducing seal productivity
- prey reductions could effect polar bear condition and ultimately
cub production and survival
- Changes that alter the period of ice coverage could affect distribution
and impact polar bears
- bears may spend greater amounts of time on land
- extended use of terrestrial areas would ultimately effect
physical condition of bears when forced to rely on fat stores
- decreased physical condition could effect production and
survival
- bears using deteriorating pack ice may experience increased
energetic costs associated with movements and swimming
- Denning could be impacted by unusual warm spells
- access to high quality denning areas may be limited or restricted
- use of less desirable denning habitat could have impacts
on reproduction and survival
- rain or warming could directly cause snow dens to collapse
or be opened to ambient conditions
- loss of thermal insulative properties in opened dens could
affect litter survival
As a case in point, in Western Hudson Bay researchers have collected
demographic information on polar bears since 1981. Over this time
frame and location the sea ice breakup has been occurring earlier. The earlier
breakup has been related to the poorer condition of polar bears
and there is a correlation between the earlier breakup and a decadal
scale pattern of warming air temperatures during the spring between
1950 and 1990. It appears that earlier breakup caused by warmer
temperatures has resulted in declines in physical and reproductive
parameters of polar bears in this area. This is the only study to
date to demonstrate the effects of changed environment resulting
from climate changes, and a corresponding effect on polar bears.
Climate change is not uniform in all areas of the Arctic, however. Since Hudson Bay is located at the southern most extent of the range
of polar bears, findings here may be a forewarning of changes to
come in future years for other areas of the Arctic. Clearly, climate
change and its effect on sea ice and polar bears should be closely
monitored in future years.
Environmental contaminants in the form of persistent
organic pollutants (POPs) pose an additional area of increased concern
for polar bears. Recent documentation of baseline contaminant levels
in the circumpolar environment and in key species has dramatically
expanded the knowledge of regional presence and levels of these
pollutants over the past 10 years. Polar bears, as an apical predator
that tends to amplify the accumulation organochlorines compounds, are
a perfect candidate for studies in evaluating trends. We now know
that polar bears inhabiting certain areas of the Arctic exhibit
elevated levels of organochlorines, particularly PCB's (poly chlorinated
biphenyls) while populations inhabiting other areas have lower levels.
Laboratory experiments involving elevated levels of organochlorines
have been associated with a range of effects including neurological,
reproductive, and immunological changes. Studies are continuing
to evaluate the effect of persistent organic pollutants on essential
life functions of polar bears and other marine animals with an emphasis
on evaluating immune and hormonal systems.
International involvement in polar bear conservation
dates back to 1965 when scientists from Canada, Norway, Denmark,
USSR, and the United States met in Fairbanks to discuss polar bear
conservation due to widespread concern that populations were being
over harvested. Until this time there had been very little management
of polar bears in the Arctic and no coordinated effort among arctic
countries. Harvest rates were rising rapidly in most areas except
Russia which had enacted a ban on hunting in 1956. The Fairbanks
meeting resulted in the formation of the IUCN/SSC Polar Bear Specialist
Group (PBSG) whose mission was to coordinate polar bear research
and management programs on an international basis and to exchange
information on each country's programs.
Members of the PBSG and the countries they represent
developed and negotiated the International Agreement on the Conservation
of Polar Bears (Agreement), which was signed in Oslo, Norway in May,
1973. Among other conditions the Parties agreed through Article
VII to "conduct national research programs
on polar bears, particularly research relating to the conservation
and management of the species. They shall, as appropriate, coordinate
such research with the research carried out by other Parties, consult
with other Parties on management of migrating polar bear populations,
and exchange information on research and management programs, research
results, and data on bears taken." The PBSG meets every
three to five years with a goal of advancing the principles of the
Agreement. The most recent meeting was held June 2001 in Nuuk, Greenland.
The proceedings of the working group meetings are published in the
IUCN series.
Highlights of recent activities include: conducting
ecotoxological studies to evaluate potential effects on polar bear
immune and hormone systems in the Svalsbard Island complex; continuing
efforts to refine population boundaries and better understand sustainable
harvest levels or the effects of harvests on populations; evaluating
new techniques to conduct aerial population surveys; evaluating
the relationship between bears, seals, and sea ice conditions; population
genetics studies; and research to evaluate the effectiveness of
thermal sensory technology to detect polar bear dens beneath snow;
and.
The IUCN PBSG recently developed a web site that can
be located at http://pbsg.npolar.no.
This site includes a wealth of information including presentations
from the last meeting, at Nuuk, Greenland, June 2001, population status
and trends, a summary of the main issues facing polar bears (climate
change, development, contaminants, and hunting), polar bear life
history facts, members list and contacts, and a list of other pertinent
links.
Gallery of Polar Bear Photographs
General Biology and Organizations
International
Association on Bear Research and Management
Polar
Bears International (formerly
Polar Bears Alive)
U.S. Geological
Survey
U.S.
Fish and Wildlife Service
Climate Change
Intergovernmental
Panel on Climate Change
Arctic Council
(International Arctic Science Committee)
Bering Sea
Impact Assessment - Alaska
Barents
Sea Impact Study - Norway
United Nations Framework
Convention on Climate Change
Arctic Monitoring
and Assessment Program
Contaminants
Stockholm
Convention on Persistent Organic Pollutants
U.S. Environmental
Program Persistent Organic Pollutants
Canada:
Northern Contaminants Program
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