Environmental Engineering Reference
In-Depth Information
The American pika, a small rodent that lives on the slopes of
mountains in the western United States, can overheat when tempera-
tures hit 80 degrees. Over the past century, these creatures have kept
climbing, reaching new ranges that can be 1,300 feet upslope. When
they reach the highest point in the landscape, it will be the end for
them. Probably few people other than zoologists who specialize in
rodents will lose much sleep over the possible decline of the pika,
but humans may see some of their most beloved species decline or
disappear.
Polar Bears One warm, fuzzy, and charismatic mammal whose fate is
causing concern among many people is the polar bear. Polar bears spend
much of their life on the Arctic ice and use it as a hunting ground for
fat and meaty seals. When ice on Canada's western Hudson Bay started
to break up earlier than usual—three weeks earlier in 2004 than in
1974—the bear population fell by 21 percent in seventeen years. 6 Shrink-
ing ice has also been blamed for cannibalism among polar bears off
Alaska, something not seen before 2004. The seals may be pleased, but
many humans are not.
Although data are very fragmentary, scientists say that the polar bear
population has more than doubled since the 1960s and that 20,000 to
25,000 of them can be found across the Arctic region from Alaska to
Greenland. 7 Nevertheless, in September 2007, the U.S. Geological Survey
predicted that two-thirds of the world's polar bears could die out in fi fty
years. 8 The National Resources Defense Council cautioned that “birth
rates among the polar bears are falling, fewer cubs are surviving, and
more bears are drowning.” 9 The World Wildlife Fund believes that polar
bears could become extinct by the end of this century, and the Polar Bear
Specialist Group agrees. 10
Are these urgent calls to action justifi ed? What do we know about the
living habits and survival potential of polar bear populations? Contrary
to media portrayals, they are not fragile “canary in the coal mine”
animals, but robust creatures that have survived past periods of extensive
deglaciation. The oldest polar bear fossil found so far is 130,000 years
old, suggesting that the species is at least 200,000 years old and has
persisted through past interglacial periods when global and Arctic tem-
peratures were at least several degrees warmer than today (and sea level
was 15 feet higher than today's level) and when levels of summertime
Arctic ice were likely considerably lower than today. 11 The last warm
span between ice ages peaked about 125,000 years ago. Although many
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