The Boundary Waters Canoe Area surrounding Ham Lake—where Frelich and his colleagues were trapped—is the most heavily used chunk of the U.S. National Wilderness Preservation System. The boreal forest, its lakes, hiking trails, and breathtaking wildlife entice some 200 000 visitors every year, providing roughly 18 000 tourism jobs that pay a total of $240 million in wages. Global warming and shifting tree ranges threaten all of that.
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“Everyone’s worried about losing the forests,” Frelich says. “Resort owners, people who own cabins up there, local outfitters that rent camping gear—and the tourists themselves. If the forests burn too much, or if they descend into savannah, or can no longer support the iconic wildlife—like moose, lynx, and boreal owls—that people have come to expect, tourism will dry up. Because no one will want to vacation there.”
And it’s not just the tourism industry that will suffer in a warmer North Woods. The region as a whole supports about 1000 forestry and logging jobs, which pay about $50 million in wages. On top of that, some individual species have become industries unto themselves—for example, the sugar maple.
Maple syrup production is heavily dependent on climate. The flow of sweet, sticky tree sap that eventually covers your pancakes is governed by changes in air pressure, which are in turn governed by changes in air temperature. When the temperature drops below freezing, the tree acts as a giant suction system, pulling the sap out of its branches, down into its roots. When the temperature rises above freezing, this action is reversed; the pressure gradient forces sap up from the roots, through the branches and out of any holes—including ones that syrup makers have drilled for taps.
Traditionally, climate in northeastern North America—from Minnesota to Maine, to southern Ontario, Quebec, and New Brunswick—has provided the optimal freezethaw patterns for this process, which syrup makers call “sugaring.” But in recent years, the transition from winter to spring has accelerated, leaving fewer freeze-thaw cycles and less sap overall. Warmer daytime temperatures in Canada have increased the number of freeze-thaw cycles, and some experts say that Canada is already in the middle of a syrup boom. “If current trends continue,” Woodall says, “it’s not impossible that the entire industry could one day be lost to Canada.”
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For Woodall, the stakes are both more basic and more terrifying than the loss of any given industry: societies that don’t protect their forests fail, he says. And it’s easy to see why. “Forests stabilize soil and clear water of pollutants,” he says. “In fact, the vast majority of Americans drink water that comes from a forested watershed. That means trees are as crucial to our survival as the water we drink.” The loss of forests is also another positive feedback loop that threatens to exacerbate climate change: forests are an important carbon sink—they store trillions of metric tons of CO2 in their plants and soils. When they are burned, or die and decompose, much of that carbon is released into the atmosphere (see Chapter 11 for more on the ecosystem services of forests).
To be sure, some people and places will benefit from climate change. In Greenland, for example, warmer temperatures have enabled farmers to grow a wider variety of crops than they have been able to in the past. Warmer weather during the summer months has also opened the Northwest Passage—a long sought-after shipping route north of Canada through the Arctic Ocean—which would significantly reduce the transport time for ships that otherwise have to take the southern route through the Panama Canal. High-latitude land in Canada and Siberia will likely become warmer and more habitable—lessening the incidences of cold-related health problems and deaths.
But other areas will suffer more harm than good. Coastal flooding is already affecting low-lying areas, from Bangladesh to New Orleans. Extreme weather has already begun to claim both valuable crops and human lives. And infectious tropical diseases have begun to migrate north of their traditional range (dengue fever, for example, has made its way from Africa and South America into Texas and Florida).
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