Polar bears on thin ice

November 12th, 2013 by
Polar Bear on sea ice, Arctic National Wildlife Refuge, Alaska

Standing on thin ice a polar bear curiously approaches. Polar Bear ice, in the Beaufort Sea, Arctic National Wildlife Refuge, Alaska. Please click on the image above to view a larger version of this photo.

Hey Folks,

Here’s a polar bear photo from my trip to the arctic last month. Given the predicament bears in the Beaufort Sea find themselves in (declines in accessible food due climate change), I thought the image a particularly relevant one.

Polar bears are classified as marine mammals, not, like their darker coated brethren to the south, mammals who earn their living on good old terra firma. Polar bears hunt, almost exclusively seals, and particularly 2 species of seals; primarily ringed seals (Phoca hispida) and less often, bearded seals (Erignathus barbatus). That alone makes polar bears particularly susceptible to population declines; any animal whose primary food source s merely one or 2 other species is somewhat vulnerable. This applies no less to herbivores who may exist on one or 2 types of plants. A crash (or boost) in the abundance of their food source will have an enormous impact on the population of their own species; a look at the lynx and the snowshoe hare cycles illustrates this.

So climate change has shifted the world for the polar bear; here’s a quick, and rough, summary of how.

The most productive waters in the arctic ocean are under sea ice, in the shallower areas over the continental shelf. Deeper water doesn’t hold light as well, and so tiny little critters like plankton and what not don’t do as well. They feed on the algae that grows and collects on the bottom of the sea ice. So where the plankton population is higher, so too is the population of the little critters that feed on plankton; shrimp and such. Fish eat shrimp, and bigger fish and regular size fish, and seals eat bigger fish. Where there’s no sea ice, there’s no algae growing. And if there’s no algae, no plankton, no shrimp, no regular size fish, no big fish, no seals and, you guessed it, skinny, hungry polar bears swimming around wondering why they can’t find any food.

And the arctic ocean waters are not a veritable wealth of other primary food sources; particularly in the deeper water, out from the continental shelf.  Polar bears primary habitat is closer to the shoreline, not thousands of miles out from land on the ice; because even though there is plenty of ice over that deeper water, there is much less primary food sources living under that ice; shrimp and fish, etc.

As climate change causes the ice pack to retreat from land, further out to sea, the water under the ice pack gets significantly deeper, and less productive. Polar bears must follow the ice, as they’re not adapted to hunt successfully on land or in open water. In following the ice, they are (in many places) struggling to find adequate food sources; because their food sources, the seals, can’t find adequate food sources either. And on down the chain.

So it’s all about productive habitat, surprise surprise. The threat to the polar bear populations around the world isn’t, much to the chagrin of countless NGO organizations who like to talk endlessly about drowning polar bears, that they can’t swim. The polar bear is an incredible swimmer, capable of moving through the water vast distances, efficiently. They do so regularly. They don’t actually hunt and catch their prey in open water; a polar bear can’t out swim a seal (generally – though they do use the water to sneak up on seals resting unsuspectedly on an ice flow). Polar bears catch seals on the ice. And the seals are found in higher numbers on ice that sits above biologically productive water. And that water is shallower, over the continental shelf. In the Beaufort Sea region, that’s an area that extends out roughly 100 miles or so from the shoreline.

What all this means is that as the ice pack moves farther out from shore, the polar bears get hungrier. And when they go hungry, in this arctic environment, they die. Climate change is affecting the ice pack every year. The retreating ice pack is a function of a warming arctic environment.

So make an effort to reduce your carbon footprint. If you’re interested, here’s a page on Expeditions Alaska website talking about the kinds of things we can do to reduce our impact.

From a photographic standpoint, which of the images do you like more? The one above, or a vertical composition I shot moments later?

My complete selection of stock polar bear photos found here.

Cheers

Carl

Polar bear on thin ice, Beaufort Sea, Arctic National Wildlife Refuge, Alaska.

A curious polar bear standing on the thin sea ice at the shoreline of the Beaufort Sea. Polar bear, Ursus maritimus, Arctic National Wildlife Refuge, Alaska. Please click on the image above to view a larger version of this photo.

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5 Responses to “Polar bears on thin ice”

  1. Very informative Carl.

  2. Mark says:

    Great writeup Carl and perfect accompanying shots.

  3. Excellent work, Carl, and timely info.

  4. Carl D says:

    Thanks Richard, I appreciate that.

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Skolai Images

Welcome to Skolai Images, nature photography blog from Carl Donohue. I'll post on a variety of topics that in some way or another relate to nature photography, including also travel and adventure photos. Thanks for visiting and feel free to add your thoughts. avatar



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