April 14, 2011

Are Polar Bears a Good Indicator for the Effects of Climate Change? ~ Ashley Warner

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We have two ways to go: one, to realize we are Nature, and it is us. Two, to continue to exploit it. The choice is ours. Our children, and their children, however, won’t have that choice. ? Repost from @discover_oceans – There are 19 subpopulations of polar bears in the world, 13 of which can be found in Canada. Some of these bears live year-round on the ice, but for populations such as the Hudson Bay bears, the ice proves an ephemeral habitat. The bears simply depend on sea ice to make a living, "No sea ice means no seals. And no seals means no polar bears." I think it's very clear that we're going to lose the vast majority of them, if not within our lifetime, then certainly within the lifetime of our children. ? Image by ©Arne Naevra – ?Follow us for more @discover_oceans ?❤

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In recent years, much has been made of the plight of the polar bear as proof positive of global warming. While it is true that climate change poses a serious threat to individual species, all factors impacting the animal’s survival must be measured and weighed. However anyone with an online biology degree will tell you focusing too much on one species can lead many to overlook other, more reliable indicators.

Scientists frequently base their concerns over the decline of the polar bear on changes in the Arctic environment. The assumption is that number of polar bears is decreasing due to fact that the Arctic ice (which houses much of their prey, such as bearded seals and ringed seals) is rapidly melting. Yet in spite of the irrefutable fact that the Arctic ice is diminishing, populations of both seal species are thriving.

As such, it seems that polar bear populations are not the best sign of global warming.

In fact, it is likely that there are a variety of factors influencing the decline of the polar bear, if they even are in decline. The species are found in five countries (Greenland, Norway, Canada, Russia and the United States) and biologists further divide them into 19 subpopulations.

However, according to a report by the conservation organization Polar Bears International, seven of these subpopulations have not bee studied adequately enough to provide sufficient statistical data. Of the remaining twelve, the report claims that one is increasing, three are stable and eight are declining. When one considers that the total population is estimated to be only 20,000 to 25,000, it is easy to see that even minor shifts in the numbers can have significant consequences.

While polar bears may not be the best metric against which to measure climate change, a careful analysis of the world’s oceans may prove to be far more fruitful. For instance, one good indicator of global warming is the rising sea level. Increasing temperatures are causing mountain glaciers, ice caps and ice sheets to melt, the excess water flowing down to the oceans and resulting in a higher sea levels. The United States Environmental Protection Agency (EPA) reports that levels rose between 4.4 and 8.8 inches during the twentieth century, which may not seem significant, but makes a much larger difference in areas where the tide is strong.

Sadly, it is likely this effect will only increase in the coming years. In fact, the United States Geological Survey reports sea levels are continuing to rise one to two millimeters per year. However, simply measuring the increase in sea level over time alone is not to enough provide positive proof of global warning, since only the United States, Europe and Japan have enough buoys in place to record reliable data.

Furthermore, the EPA report also cautions that one must specify a particular part of the world they are obtaining their measurements from, since areas such as Louisiana, where the land is sinking, will record higher changes than Alaska, where the land is rising.

A better way to gauge the health of the planet’s oceans would be to take accurate, extended measurements of their salinity and temperature. One way to monitor these two factors naturally is by pay attention to coral reefs as they are particularly susceptible to both. In fact, a report published by the Secretariat of the Convention on Biological Diversity, claims as much as 88 percent of the Southeast Asian coral reefs could be lost within three decades without stringent intervention.

The status of inland glaciers is another important indicator of climate change. Worldwide, glaciers have been melting at accelerated rates. The United States Geological Survey estimates that about 40 percent of Iceland’s glaciers will be lost by the end of this century. Glacier National Park may be an anachronistic misnomer within the next 150 years.

Ultimately when too much attention is paid to polar bears, the region that receives the focus is the Arctic. However, the Antarctic and Greenland have the potential to cause much more devastation if they become ice-free. The United States

Environmental Protection Agency considers both the Greenland and the West Antarctic ice sheets to be particularly vulnerable. Should the Greenland ice sheet melt, the EPA estimates it could raise sea levels by as much as 23 feet. Since it is not predicted to collapse suddenly, it could take several thousand years to melt completely. On the other hand, the West Antarctic ice sheet is not as stable and could eventually be prone to sudden collapses. It contains sufficient ice to raise sea levels by 17 to 20 feet, conceivably within a few hundred years.

Overall, no species does well with change. When faced with habitat changes or the invasion of foreign species, it may take many thousands of years for a species to adapt (assuming it doesn’t go extinct). As such, the polar bear, a species that has evolved over millennia to survive in a narrowly defined environment will be most susceptible to minor changes, which in turn makes it a poor indicator for the effects of climate change. Examining a greater variety of species from several different habitats offers a better picture of how the climate is changing. This data, integrated with various other statistics, can provide more accurate predictions regarding the future of the planet.


Ashley Warner is a graduate student working toward her Masters in Conservation Biology. She currently resides in Washington state.

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