The polar bear is perhaps the quintessential image of climate change. As if the iconic white bears don't already have enough to deal with, they face even greater peril in the form of man-made pollution.
A recent review of research gathered over the course of more than a decade suggests that toxic chemicals are reaching the Arctic region via air and water. The review, published in the journal Environment International, found that this pollution includes toxins such as mercury, chemical coolants, and pest control agents.
The BBC reports, “Such chemicals are often fat-soluble and accumulate in the fat of many animals, which are then eaten by top predators such as polar bears. These top predators are then exposed to increasingly concentrated levels of toxins.”
Veterinary scientist and polar bear expert Dr. Christian Sonne of the Department of Arctic Environment in Denmark conducted a review of all pertinent research on the link between Arctic contaminates and polar bear health. He was previously part of a research team which found pollutants and environmental stress, such as shrinking sea ice, appear to be negatively affecting polar bear populations.
Dr. Sonne’s new analysis of more than 200 organ and skull tissue samples taken from 80 bears from 1999 to 2009 can show that such pollutants and toxins correlate with ill-effects to polar bears, not that they cause the effects. For that very reason, he studied two of the Arctic’s other top predators — the Norwegian Arctic fox and Greenland sled dog.
In 2003, researchers started a two-year study in which they fed both clean and contaminated whale blubber to Arctic foxes. What they found was the foxes that were fed the contaminated food suffered from harmful effects. Similar effects were found in similar studies of Greenland sled dogs.
Dr. Sonne says the studies on polar bears correlate with the findings of the sled dog and fox studies, but that it is still not conclusive enough to result in a “cause and effect” conclusion. Dr. Sonne said, “So including dogs and foxes as model species is important [because] you use species that are much like polar bears, and the species were exposed to similar food items as polar bears."
Unfortunately, the impact on the bears is likely to be even greater than in the foxes or sled dogs because of the added stress of climate change on the polar bears.
As the levels of sea ice decline, the bears fast for a longer period of the year. This means they will feed on less-contaminated seals but will burn more of their own fat for sustenance … fat that is already housing toxins. The result is they release greater concentrations of toxins from their fat stores into their blood, says Dr. Sonne.