The New World Order
Unseasonable winter warming also affects snowshoe hares in another way: waning fall daylight triggers the hare’s brown summer coat to turn snow white; usually camouflaged against the snow cover, the hare will stand out against a bare terrain in winter and becomes an easy target for raptors.
While much of the worldwide discussion about global warming focuses on rising sea levels, water levels in the Great Lakes basin could drop significantly as a result of increased evaporation due to warmer summer air and reduced ice cover in the winter.
Lower water levels help speed up overall warming trends. Natural Resources Canada (NRC) estimates that average lake water temperatures have increased by 1.5 C in the last 30 years, leading to more algae blooms and lowoxygen “dead zones” in lakes. All of this is bad news for coldwater species such as lake trout. For example, warmer water causes an increase in their metabolic rates. A 16- year analysis of trout in an Alaskan lake concluded that if average July temperature increases continue as projected, juvenile “lake trout will not survive their first winter.” There simply would not be enough food available to compensate for the extra energy their increased metabolic rate in summer would require.
Warmer water temperatures, however, are a boon to species such as smallmouth bass. NRC estimates that in the past two decades, populations of warm-water species have increased by 60 percent, while coldwater species have declined by the same percentage.
Given their skin- close connection to the environment in which they live, amphibians are an excellent indicator of habitat health. The signs they are providing are not good. While spring flooding and summer drought would have obvious repercussions for pond dwellers, a few extreme winter warm spells earlier this decade alerted herpetologists to what global warming could mean for frogs.
During warm periods in January 2005 and again two winters later, hibernating frogs became active, behaving as if spring had arrived. When temperatures dropped again, many frogs were caught out in the cold. Wood frogs in particular, which dwell below ground, died off in large numbers. “It’s absolute death when the cold comes again and they are trapped above ground,” says Ken Storey, a Carleton University professor and Canada Research Chair in Molecular Physiology. (The interrupted hibernation cycle affects the entire food chain, from insects that emerge early as adults only to die when the sub-zero temperatures return, to speculation about exhausted bears that deplete their fat stores while foraging for food early in the season when supplies are limited.)
To many people, polar bears are the poster species of climate change, and for good reason. Warming effects are accentuated at the poles – a recent report in Science calculated that the Arctic is the warmest it has been in 2,000 years – and, as a result, the peak amount of winter ice cover within the Arctic Circle has been declining by an average of more than 40,000 square kilometres a year, according to the U.S. National Snow and Ice Data Center. Less ice means polar bears have to swim longer distances to hunt, and many drown trying. It also forces them onto dry land earlier in the spring to scavenge for food, leading to increased conflict with humans, typically with fatal consequences for the bears. A 2007 U.S. Geological Survey report estimated that two thirds of the world’s polar bears could be gone by 2050. The situation is already so desperate that there are reports of polar bears becoming cannibalistic.
While some birds, like snow geese, may thrive in a warmer climate, many Carolinian species may find themselves on a forced exodus from their southern range. In 2004, the U.S. Department of Agriculture (USDA) released their Atlas of Climate Change Effects in 150 Bird Species of the Eastern United States. The report concluded that “about half of the species show a potential decrease of at least 25 percent of their abundance…while about a fifth of the species show a potential increase of at least 25 percent in their abundance.”
Included in the group projected to decline is the ruffed grouse, with the USDA predicting “the withdrawal of this species from the coastal regions of the Northeast and from… the entire Great Lakes region.”
The impact on grouse would be a direct result of the projected “near extirpation” of paper birch trees from the same region. The tree’s catkins and buds are a major food source for the grouse. And while it is relatively easy for birds to migrate to greener pastures, trees have a number of obstacles blocking their path.
“It’s hard for trees to move. It’s not just the trees, everything – pollinators, soil fungus, precipitation levels, the length of the seasons – has to move with them,” explains Sean Fox of the University of Guelph’s Arboretum.
Meanwhile, researchers in the northeastern U.S. already have grave concerns about the survival of paper birch. While acidity levels have dropped from their headline grabbing peak in the 1970s and 1980s, acid rain continues to fall (the Alberta tar sands are a growing contributor), depleting the quantity of acid-buffering calcium in the soil. Without this essential nutrient, the birch trees’ immune systems are weakened, making them increasingly susceptible to pest infestations and storm-induced mass die-offs, both of which are projected to increase as temperatures rise.
Allan Britnell is a Toronto-based is a Toronto-based freelance writer and editor.
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