The author of today’s post, Lisa Moore, Ph.D., is a scientist in the Climate and Air program.
A frame from an Environmental Defense ad campaign about the danger of unchecked global warming.“Most Polar Bears Gone by 2050“. You may have seen that headline in the news this week. The study behind this depressing conclusion could land polar bears on the list of threatened species under the Endangered Species Act.
Polar bears depend on the sea – and sea ice – for food. Most often they dine on ringed seals, which they catch by hanging out on sea ice next to seals’ breathing holes. Without sea ice, they can’t get enough food to survive. Unfortunately, summer sea ice has been declining rapidly, raising fears for polar bear survival.
In response to a lawsuit from a number of environmental groups, the U.S. Fish and Wildlife Service recently proposed protecting polar bears under the Endangered Species Act. As part of the decision-making process, the Department of the Interior commissioned a study of polar bears, and how global warming is affecting them. The resulting nine-part report evaluates the distribution and abundance of polar bears in each of four different eco-regions.
Biologists have been studying polar bear populations for years, so they have a good understanding of how sea ice dynamics – particularly the length of the ice-free season – affect polar bear survival. The authors combined this information with climate model simulations of sea ice extent under a business-as-usual scenario of greenhouse gas emissions. The results were sobering.
Polar bear populations in the Western Hudson Bay and Southern Beaufort Sea are declining, and this trend is linked to disappearing sea ice. Polar bears in the Hudson Bay and northern Russia could disappear by mid-century. Polar bears of northern and eastern Greenland may hang on for 75 years. In the archipelagos between northeastern Canada and northwestern Greenland, polar bears are likely to survive through the end of the century, though in smaller numbers.
And these conclusions are conservative. Sea ice models have generally underestimated sea ice loss.
This coming January, the Fish and Wildlife Service is expected to make a recommendation to the Secretary of the Interior on whether or not to add polar bears to the list of threatened species. The legal outcome is a few months away, but in the meantime this comprehensive scientific report hammers home the message that global warming jeopardizes Earth’s stunning biodiversity, including some of its most loved, iconic species.
This is deeply alarming, but not a reason to give up. Remember, these results are for a business-as-usual scenario, and scientists have shown that bold action today can minimize global warming. This report is yet more motivation to get going in the fight against global warming.
5 Comments
Good article here at the National Snow and Ice Data Center site. Very easy reading and great charts. It says the Arctic sea ice is now at record lows, mainly because of wind patters, high pressure over the area, and an unusually high number of clear days. The melting has slowed somewhat in the last part of August the site says, but they expect more melting to occur and will update their site regularly.
http://nsidc.org/news/press/2007_seaiceminimum/20070810_index.html
From the site:
“All of this leads us to ask: why has the melt season progressed so quickly? The answer lies in a combination of high temperatures, changes in the age and thickness of ice, and fluctuations in atmospheric circulations.” (My coment as a former meteorologist:record number of clear days because of the upper wind pattern being stuck as a ridge of high pressure over that area.)
There’s also the fact of all the soot making the snow fields dirty and darker, thus obsorbing more heating sunlight instead of refecting it (per another post by a Environmental Defense author a few weeks ago).
Plausable, Lisa, but don’t forget the research over the last twenty years which shows that polar bears and higher mammals have bioaccumulated much of the PCBs and chlorinated pesticides which got to the Arctic via the “grasshopper effect”. In fact, Inuit women have the highest PCB concentration in mother’s milk of anyone in the western hemisphere except perhaps for a group in Nicaraugua.
How can we be sure that we’ve not decreased the productivity of polar bears via estrogenic pesticides, dioxins and PCB’s?
Hi CaptainLaser!
Thanks for your comment.
Contaminants are definitely a concern for polar bears and other animals (including people!). The USGS report does consider other factors besides sea ice, although sea ice extent and ice-free days are the primary focus.
The authors found significant relationships between sea ice cover and several measures of polar bear nutritional status and population dynamics (such as mass, growth, and cub recruitment). For example, in the Southern Beaufort Sea, the bear population starts to decline when there are more than 125 consecutive ice-free days.
Could contaminants play a role in current declines in polar bear numbers? Certainly the report does not rule out this possibility, and I’m sure that future research will explore the effects of contaminants on population size.
However, one interesting result in the report was that in the Southern Beaufort Sea, polar bears are declining even though these bears have lower contaminant levels than other populations (some of which are currently stable). Also, a 2005 study found that in polar bears from Svalbard, Greenland, Canada and Alaska, tissue concentrations of many contaminants have actually decreased over time.
Of course this isn’t to say we shouldn’t be concerned about or try to decrease contaminant levels! Just that the data so far point to sea ice dynamics as a critical factor for today’s polar bears – and one that will become increasingly important in the future.
Hope that helps.
cheers,
Lisa
Lisa, it is nice to hear from someone with knowledge and a peaceful way of communicating it, and to see the good questions and comments as well.
I put the polar bear and polar ice discussion into the context of a planet that will see tremendous changes in the 21st century – oil slowly declining in availability, temperatures rising, and food and water shortages that have already started in many parts of the world. All of these current or projected events seem to point to two required actions by people: 1) walk lightly – use less, conserve more, live smarter, and 2) reduce population to a long-term maintainable level, which will reduce greenhouse gas production, pollution, and stress on food and water sources.
These are both big challenges to implement in the USA, let alone globally. But all it would of course help the polar bears and other endangered species, and our own civilization and survival. That is the big picture of environment, as I see it.
Look folks, its all going to hell in a handwoven basket. The Earth is dying and there is nothing we can now do about it.
I suggest everyone get the four “G”s, and hunker down for some Mad Max action, Guns, Grain, Ground and Gold. Some oil stocks would be nice as the USD$ is in its death throws. Anyhow, peak oil is here and western civilazation will collapse, so lock and load. Start your garden now and get some goats (if you still want to have goat chesse, which I love). Learn to barter, and something with which to barter with (other than manipulating a computer).
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[…] Two-thirds of polar bears could disappear by 2050. According to a federal report, "because the observed trajectory of Arctic sea ice decline appears to be underestimated by currently available models, this assessment of future polar bear status may be conservative." […]
[…] To hunt for food, polar bears need summer sea ice, which is vanishing. We heard about one starving mother bear who weighed less than 200 pounds at one point. Luckily, when caught and weighed some months later, she was back up to 1000 pounds. […]