Anyone doubting that need only consider Minnesota, where sportsmen have already felt the heat.
Over the last 40 years, average temperatures in Minnesota have risen by 12 degrees in the winter and 4 degrees in the summer, forcing moose to spend more time immersed in water to cool down, and less time feeding. The result has been a weaker herd, more susceptible to disease and less successful at breeding, says Dave Schad, director of the state's Division of Fish and Wildlife. Between the 1980s and 2003, the moose population in northwest Minnesota dropped from 4,000 to 237, forcing the end of hunting seasons. The northeast population has experienced a similar drop, and the hunting season there has been curtailed.
Another icon of the Minnesota outdoors, the walleye, is facing a similar crisis. The small increase in water temperatures will be fatal to walleyes in some shallower lakes, while in others it will kill the species' primary food sources.