Steven Amstrup will be speaking at the Wildlife Conservation Network Expo
in San Francisco on October 11th, 2014.
In 1773, an expedition headed by Constantine John
Phipps, the Second Baron Mulgrave, embarked on a dangerous journey North—to see
how far they could go before having to turn back. In his report at the end of
the exploratory voyage, he notes that every precaution was taken to ensure a
successful voyage—extra clothing on board for when "the higher
latitudes" were reached, spirits for use by the sick, and life boats
designed to carry the crew of both ships, should one be lost. Along the way,
Phipps encountered and described for the first time, a most magnificent animal—one
that has captured the fascination of modern day explorers and the public alike
for centuries.
Robert Bateman, Oil on canvas
"We killed several with our musquets [sic], and the seamen ate of their
flesh, though exceeding coarse," writes Phipps of the polar bear (Ursus
maritumus), large numbers of which he saw on islands and adjacent ice
fields. Standing four feet tall at the shoulder, and weighing a whopping 610
lbs (without head, skin or entrails—a result of being prepared for
consumption), the polar bear was and still is the largest land predator on
Earth—a carnivorous, complex, and, sadly, highly threatened bear.
Polar bears exist only in the Northern Hemisphere, preferring to live on the
edges of great stands of sea ice, where the water is shallow and their favorite
prey, the ringed seal (Phoca hispida), can be consumed. In the winter as
the ice grows, they migrate with it, as much as 1,000 kilometers to stay with
the southern edge of the pack ice. Thus seasonal melting and freezing of the
ice has a significant impact on their ability to feed, and ultimately, their
survival.
Polar
bear in Alaska. Polar bears are the world's largest land carnivore
Polar bear young, besides melting even the stoniest of hearts with their teddy
bear looks, are extremely altricial, or underdeveloped, when first born. Female
bears, nearly 400 to 500 times as large as their miniscule cubs, remain within
their dens, nursing their cubs with fat-rich milk till they weigh as much as
100 kilograms by the time they complete their first year.
After Phipps' exploration, not much more became known about this elusive mammal
to scientists for hundreds of years, occupying as it did some of the most
desolate landscapes on the planet. A large chunk of what we know today has
derived in some form from the incredible research of a modern day
explorer—Steven Amstrup.
As Chief Scientist for Polar Bears International, Amstrup has worked diligently on polar bears for
over 30 years. He radio-collared some of the first bears and discovered that
annual activity areas for 75 tracked females averaged at a stunning 149,000
square kilometers. His recent work, published in the journal Nature,
highlighted the cost of global warming to these incredible animals and the sea
ice they so closely depend on.
Steven
Amstrup with a pair of polar bears during a research expedition.
According to Amstrup, to safeguard the polar bear "the only solution is to
stop the rise in CO2 and other greenhouse gases. All other management actions
are treating only the symptoms and not the disease."
The image shows sea ice coverage in 1980 (bottom) and 2012 (top), as
observed by passive microwave sensors on NASA's Nimbus-7 satellite and by the
Special Sensor Microwave Imager/Sounder (SSMIS) from the Defense Meteorological
Satellite Program (DMSP).
Multi-year ice is shown in bright white, while
average sea ice cover is shown in light blue to milky white.
In the last 25 years, as global temperatures have increased, the extent of
sea-ice in the Northern Hemisphere has abruptly declined by at least a million
square kilometers. Through extensive capture and release programs, scientists
have now recorded that body weights of female polar bears have declined. The
numbers of independent yearlings they produce have also fallen, increasing the
number of years between two successful births. At the same time, sea-ice in
areas such as the Hudson Bay has been melting earlier each summer.
In a recent interview, Amstrup talked about the fate of the polar bear if we
continue to fail to control global temperature increases, and described how the
world's biggest carnivore are an important marker for our own fates.
Steven Amstrup will be presenting at the up-coming Wildlife Conservation
Network Expo in
San Francisco on October 11th, 2014, an event which will be headed by Frank
Pope and Dr. Iain Douglas-Hamilton of Save the Elephants.
INTERVIEW
Journalist: You have been conducting research on polar
bears now for 35 years—how did you first begin?
Steven Amstrup: I started polar bear research in 1980, when the
USFWS (U.S. Fish and Wildlife Service) needed someone to take over the (at the
time) fledgling program. I was selected for the post because of my previous
experience studying bears, and faith from my lab director that I could hit the
ground running. I arrived, established objectives and areas of focus, secured
outside funding, and built the program from a one-man show to a staff of five
researchers.
J: Polar bears are the largest extant bears—some have been too
heavy to lift and weigh during capture. You've been closely involved with
mark-recapture studies of these bears—what is it like to work with animals this
size?
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Polar bear leaping in Spitsbergen Island, Svalbard, Norway. Photo by:
Arturo de Frias Marques
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Steven Amstrup: Polar bears truly are exciting to watch, to study, and to get up close and
personal with. Think about it-giant white bears roaming around in an
environment that looks like the surface of the moon. How could it get more
exciting?
J: How has the use of radio telemeters and satellite tracking
enlightened us as to the movements of polar bears?
Steven Amstrup: I was the first to successfully use radio telemetry
to follow polar bears and monitor their long-term movements. I learned where
they went to den and have cubs, and that they are the most mobile of all
four-legged creatures. I showed that they didn't occupy all of the same areas
every year, but did maintain multi-year activity areas outside of which they
seldom traveled. And they did not drift passively with the ice. Polar bear
researchers worldwide now use the methods I developed in the early 1980s.
J: The primary prey of the polar bear is the ringed seal—have
sea ice levels affected this prey population, and thus the bears themselves?
Steven Amstrup: We currently do not know for sure how ringed seals
are being affected by global warming loss of sea ice. They spend most of their
lives under the ice and for much of the year even their breathing holes are
covered by snow. We do know that less snow on ice and warmer temperatures in
spring ultimately will reduce their breeding success. This is because they give
birth in little caves beneath the snow surface and above the ice surface. If
they don't have sufficient snow, come spring for these "lairs", or if
the lairs melt out because the weather is warmer than usual, the pups are easy
prey not only to bears, but foxes, gulls, and ravens. But ringed seals are so
difficult to study that we don't know if those effects are yet playing out in
any areas. It is likely that at some point it will be obvious there are fewer
ringed seals, but we may not really see it coming.
Thickly packed sea ice in the Arctic from a photo taken in 1949. One day
thick, stable sea ice in the Arctic will likely be a thing of the past as the
Arctic is warming around eight times faster than the rest of world according to
a new analysis. Photo by: Rear Admiral Harley D. Nygren
J: Polar bears are defined as marine mammals because of their
nearly exclusive reliance on sea ice as opposed to land. What have been the
effects of melting ice on polar bear population sizes? Are land-denning females
more or less affected by this than males?
Steven Amstrup: They are marine mammals because they derive their
sustenance from the marine system. They probably could perform most of their
other life-history needs on land, but terrestrial arctic regions are food poor
from the standpoint of these large bears. Less ice in productive areas means
less time to hunt for seals. This is likely to affect survival of cubs first,
and we already have seen some of that in Hudson Bay and the Beaufort Sea.
Steven Amstrup with polar bear triplets
J : Does the current relatively high inter-birth interval (3
years) of polar bears restrict population replacement required to maintain
current population densities?
Steven Amstrup: Polar bears always have had a long inter-birth
interval. Only in Hudson Bay are we aware that a two-year interval was common,
and there I think it was only about 20 percent of females. But it is no longer
occurring there. The issue is not that it takes 3 years for females to wean
their young, but the fact that survival of those young is jeopardized by the
poorer foraging conditions for their mothers. Only about 3 percent of the
western Hudson Bay population, for example, is now composed of yearlings.
During the early years of my study in Alaska it was 15 percent! That means that
substantially fewer cubs are surviving their first year of life.
J: Polar bears are essentially disease free, can forego
reproduction for survival, are top predators in their environment and have
rates of adult survival in excess of 96 percent where left undisturbed (such as
at Beaufort). This makes them remarkably resilient, and yet, their numbers
continue to drop. How have these magnificent animals been overcome?
Steven Amstrup: This is a habitat issue. We
are losing about 13 percent of the summer sea ice every decade on average
(there are lots of inter-annual fluctuations, so every year is not just a bit
worse than the previous). Imagine the impact on a rancher's grazing herd if 13
percent of his land was paved every decade!
It is important to remember that declining numbers only have been documented in
a couple areas so far. The big concern is that the longer we allow the world to
warm (and the laws of physics require it to warm as long as greenhouse gas
levels rise), the less ice habitat we will have and the more polar bears will
be disappearing.
This is a point the general media have totally failed to grasp. Polar bear
range-wide disappearance is mainly a problem we will see in the future. Polar
bears in some areas are already in trouble. But as far as we know, many
subpopulations may still be doing just fine. So the larger fear is mainly for
the future—not just today. And, not just for polar bears, either. Polar bears
are harbingers of troubles to come to the rest of life on earth including us.
The good news is that because we still have many apparently healthy
populations, and we still have the ability to stop the warming in time to save
many of them. In so-doing, we will save much of the rest of life on Earth as we
know it.
J: Some estimates claim that the polar ice cap will disappear
almost entirely during summer in the next 100 years—What's going to happen to
polar bears if this occurs?
Steven Amstrup: They will be gone. And if we wait until then to
address greenhouse gas rise, no one will have time to be thinking about polar
bears. We will have so many human challenges (crop failures, drought, flood,
famine, human refugee problems where they never have occurred before), that polar
bears and other wildlife will be far from anyone's mind.
J: Your Nature paper in 2010 showed that the negative effects
of global warming could be reversed and the polar bear's environment restored
to some extent—can you explain how this is possible and how realistically this
can be achieved?
Steven Amstrup: We are currently just over 400 parts per million of
carbon dioxide. Our paper showed that, there was not an irreversible tipping
point in the sea ice, and that if we can stop CO2 rise at around 450, we will
preserve polar bears in many of their current areas. Importantly, the lack of a
tipping point means that it is not an all or nothing deal. If we overshoot 450
a bit, it is not the end of the world, and wherever we stop emissions and
temperature rise, we will have saved more ice and be better off than if we had
not stopped the rise.
J: Polar bears can be legally hunted in some areas—is over-harvesting
a threat to their numbers today given historical extirpations of bears in
certain areas through commercial hunting?
Steven Amstrup: In a few areas (e.g. western Hudson Bay), scientists
and managers are concerned about excessive harvest. Over most of the polar bear
range, however, harvest regulations adopted in the early 1970s brought human
kills under control. With a few exceptions, harvest is just not an issue. In
fact, some people seem to focus on harvest and other on the ground management
issues to intentionally distract from the critical issue of global warming.
J: Contaminants released into the arctic can build up in the
polar bear over time—has this resulted in active reductions in reproduction or
survival of the bears?
Steven Amstrup: Some individual polar bears have built up levels of
contaminants sufficiently high to compromise immune response and reproduction.
I am not aware yet, of any population level effects, however. An interesting
sidelight of global warming is the expected increased flow of contaminants into
the Arctic Ocean through north flowing rivers in Russia. Many of those large
north flowing rivers carry heavy contaminant loads and forecasts are for flows
to rise as many northern areas see increased rainfall.
J: What needs to be done to ensure the future of the bears as
well as the other species that make up their environment?
Steven Amstrup: The only solution is to stop the rise in CO2 and
other greenhouse gases. All other management actions are treating only the
symptoms and not the disease.
Along with greenhouse gas mitigation, however, there are management actions
that can be taken on the ground, and there are still needed answers to research
questions that can help assure as many bears as possible survive into the
future. Ideally, we will get our act together and stop the rise in greenhouse
gas concentrations while also adjusting harvests minimizing bear human interactions,
and doing everything we can on the ground to minimize other threats.
J: What can the layperson do to help?
Steven Amstrup: A comprehensive list of things everyone can do is
available on our website. Simple things available to all include driving less,
driving slower, not using "drive-throughs" or otherwise idling
unnecessarily. Keep our houses and businesses warmer in summer and cooler in
winter, insulate or re-insulate, and make sure our heating and air conditioning
systems are in peak working order.
Most important, is for everyone to vote for policy leaders who are interested
in moving to a sustainable—low carbon—economy, and voting with our dollars by
supporting companies and businesses that are working for sustainability. Global
warming is not about conservative or liberal or Republican or Democrat. It is
about laws of physics we have understood for over a century, and the future of
our children. Our leaders need to hear that we care about that future.
People often are frustrated that the challenge of global warming is large and
feels intractable. Yet, my work and those of many of my colleagues has shown we
still have time to save polar bears, and we know what is required to do so. All
we need to do is to inspire our fellow citizens and our leaders to convert that
possibility into action. My take home message would be that we need to do this
and we can do this.
Melting Arctic sea ice in
2000. The light blue areas are melt ponds lying on the sea ice; the dark blue
areas are open water. Both Arctic sea ice extent and volume have plunged in the
recent years. Photo by: NASA.
Citations:
- Amstrup, Steven C., et al. 2010. Greenhouse gas
mitigation can reduce sea-ice loss and increase polar bear persistence. Nature 468.7326: 955-958.
- Amstrup, S.C. 2003. Polar bear, Ursus maritimus.
Chapter 27 In Wild Mammals of North America: biology, management, and
conservation. Edited by G.A. Feldhamer, B.C. Thompson, and J.A. Chapman. John Hopkins University Press,
Baltimore. pp. 587-610
- Phipps, C. 1773. Voyage towards the North Pole.
Downloaded from
https://ia700304.us.archive.org/11/items/voyagetowardsnor00mulg/voyagetowardsnor00mulg.pdf
on October 7, 2014
- Reid, P., S. Stammerjohn, R. Massom, T. Scambos,
and J. Lieser. 2015, in press. The record 2013 Southern Hemisphere sea-ice
extent maximum. Annals
of Glaciology 56 (69), doi:10.3189/2015AoG69A892.
