Zoo Blog
Friday, December 10, 2010
Happy 21st Birthday Berlin!
(Now what the heck is up with this climate change thing?)
Written by: Peter Pruett, Curator
There is a great and acrimonious debate presently being fought by two opposing sides of climate change thought camps. The sticking point is whether or not our climate is changing and if it is a result of human actions, specifically greenhouse gases. Greenhouse gases make it very difficult for energy originating from the sun to reflect off the earth back into space, it is trapped resulting in warmer temperatures. Another point of contention is if climate change is true or false. True or false should never be part of any discussion on climate change. Science by its nature is skeptical and is all about data supporting or not supporting and finding trends.
Polar bears are entwined with climate change because their life history is directly tied to ice sheets and ice sheets are affected by climate change. There are 19 subpopulations of polar bears worldwide. Of those 19, three subpopulations are either stable or increasing, eight are declining and for seven there is insufficient data. Data supports the trend that polar bear populations are declining. The seven populations with insufficient data at this point must be ignored. To understand why polar bears are declining let’s look at over 20 years of data for the western Hudson Bay population collected by the tireless research of biologists Ian Stirling, Andrew Derocher and others.
Evidence suggests that the warming of the arctic is well underway. Ice sheets on Hudson Bay are forming later in the year, are smaller, thinner, break apart and melt earlier in spring. Polar bears rely on ringed and bearded seals, found only on ice sheets, as their primary diet and energy source. For the last three decades polar bears are spending an extra week per decade on the shore. That means polar bears are now off the ice for at least three extra weeks per year.
Trends show that polar bear body condition has been steadily declining in the last few decades. The bears have been losing approximately 20 pounds a decade; females have lost 10% of their body length and their percent of body fat has decreased. Females come off the ice to den and give birth. Due to low body condition and not enough fat reserves, females either give birth to smaller cubs or abort their attempt at birthing. The loss of sea ice also affects sub-adult bears. They are still actively growing and any interruption or loss of vital food sources result in poor health and potential death. As a result populations are declining. These same trends are now being seen in the Southern Beaufort Sea in northern Canada and Alaska.
Barring any unusually drastic or prolonged warming event, if trends continue the western Hudson Bay population will die out in 25-30 years. The population could die out in less than 10 years if temperatures rise 1-2 degrees with an additional loss of 2 weeks of ice. Once the polar bear is removed from the western Hudson Bay area drastic ecological changes could occur. Polar bears are apex predators, top of the food chain, and their loss means smaller predators fill in the gap.
 Biologists are beginning to see the importance of apex predators. Wolves suppress coyote populations which results in decreased fawn mortality for pronghorn antelope. The loss of sharks in the Atlantic Ocean resulted in the rapid growth of cownose ray populations which then crashed the bay scallop populations. Removing raccoons along the Gulf shore line caused an increase in ghost crabs resulting in over predation of sea turtle eggs.
The unknown is how the loss of polar bears will affect the Hudson Bay region. Will seals fill the role of apex predator and how will they affect fish within the bay? If fish populations decrease, will that mean rapid growth of vegetation that could result in a change of water quality? What happens if seals face similar problems and eventually die out? What will take their place? If a predator doesn’t fill the role how will that change the ecosystem? As you can see, there are many questions without answers.
The only question we need to answer is this: are we willing to find out?
Authors note: There’s an abundance of information available as to whether data supports or does not support climate change. Please take the time to research information that is clearly cited, documented and labeled. Being well informed with the best data is the only way that any change can take place.
There are also many views of humankind’s role with the living environment; one such view is that we are stewards of our world. Stewards by definition are managers of property or the affairs of others. Our world is not property and we are not managers. We are members of the living community and as with all communities we should be good neighbors.
Educate yourself, be a good neighbor and watch life bloom. Happy Birthday Berlin!Labels: arctice, Berlin, climate change, curator, greenhouse gases, ice sheets, Lake Superior Zoo, neighbors, polar bear, science, stewards, western Hudson Bay
posted by Keely Johnson
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