Scientists who have been studying the effects of climate change on Arctic sea ice, predict that, with its seasonal contraction and expansion, we can expect ice-free summers by the end of the century if not sooner. Disconcerting images of starving polar bears and proposed plans for extensive shipping through the Northwest Passage have been of major concern to environmentalists. However, researchers are studying a myriad of subtle effects that, collectively, could have a pronounced and deadly effect on the region and beyond.
Disrupted geography from melting ice that affects hunting/searching patterns is one of the leading concerns. A study recently published in Biological Conservation estimated that in the Western Hudson Bay area, there is a 3-6% starvation rate for polar bears when there is a 120-day summer fasting period. But it is estimated that with an increase to a 180-day fasting period due to increased loss of summer sea ice, the starvation rate climbs dramatically to 28-48%.
Also, the report cited female reproductivity declining in a non-linear fashion (IE: a dramatic drop) when food searching efficiency decreases faster than sea ice habitats. In other words, it doesn't not take much in the way of a changing habitat to produce a major population crash.
Another effect of climate change and the influx of warmer waters into the Arctic is a greater exposure to parasites. A study in Polar Biology looked at the increasing prevalence of Taxoplasma gondii, a potentially deadly parasite, in polar bears and seals in Norway. It is not clear whether the parasite is being transmitted by warm water invertebrates, migratory birds, or human interactions - but climate changes can bring any or all of these potential carriers into play.
Finally, researchers from several universities and NOAA reported, in the latest issue of Nature, the possibility that several marine mammal species could become extinct over time due to interbreeding brought on by climate change. Many marine mammals are unique to the Arctic because they are geographically isolated. These isolated species have adapted to life in an ice environment. With the loss of that ice, there can be an intermingling of related species moving up from the south. But, according to the researchers, this intermingling can produce hybrids that, over time, are unable to cope with the changing environment. In essence, it's not a mixing of the best qualities but that of qualities that will actually weaken their long-term chances for survival.
As stated in a Newswise release, "In later generations, the process begins to have more negative effects as genomes mix and any genes associated with environment-adapted traits are recombined. Genes related to any trait that once allowed the animal to thrive in a specific habitat can be diluted, leaving the animal less well suited to surviving and reproducing there."
As evidence, in 2006, hunters killed a polar bear with brown patches on its fur. DNA testing revealed it was a polar/grizzly bear hybrid. Such a hybrid, borne from polar and grizzly bear contact during the summer months, may have a very poor chance of survival in the Arctic winter months.
We like simple explanations to the challenges we face, but climate change has very complex and far-reaching implications. However, the more we learn about the impacts of climate change, the better we realize that it is a challenge we must address. That much is simple to comprehend.