Sweet sap and CO2
The potential impact of climate change on sugar maples
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The change of seasons brings color and tourists to the Northeast. Photo by David Kamosky |
Editor’s Note: Nearly two years ago, a study commissioned by the Pentagon concluded that the risk of abrupt climate change “…should be elevated beyond a scientific debate to a U.S. national security concern.” But government reports and warnings about melting glaciers in Antarctica can seem far-removed, too easy to ignore. Call it global warming or climate change: rising temperatures are affecting the bottom line. Two local tales follow on how businesses in the Northeast and Midwest are sweating the warmer weather.
Every March and April pancake houses pop up along country roads in the Northeast. For a few dollars, patrons receive a hearty breakfast of pancakes, sausage, eggs and as much fresh maple syrup as they like to douse their comestibles.
Most people savoring piles of pancakes topped with homemade syrup have little appreciation that in a mere 100 years or so, the maple trees might be gone. If climate change makes Northeast winter nights as little as five degrees warmer, these cold-loving trees will die out in the region. And with them will go maple syrup, a traditional New England symbol and a business that garners $38 million in revenue each year. Although maple syrup production has been decreasing for several decades in the United States for other reasons, many researchers now say no threat is as great as the one now posed by climate change.
Until the 1940s, the United States led the world in maple syrup production. Sugar maple farms were largely family-run, with everyone pitching in each spring to collect sap. To tap a tree, producers would first bore a hole then insert a metal spigot with a hook to hang a collection bucket. When done correctly, trees are unharmed. Families would gather sap in buckets, boil it down in huge vats and bottle the product.
“Maple syrup used to be as popular a commodity as coal 100 years ago,” said Peter Gregg of the Upper Hudson Maple Producers Association. But by the middle of the 20th century the maple syrup industry began to decline. Family size decreased, there were fewer farms, urbanization drew people away from agriculture and, with the growth of the cane sugar industry, maple syrup was no longer needed to sweeten food. Eventually, maple syrup became more gourmet item than staple.
The invention of plastic tubing, in 1959, eventually replaced the traditional method of collecting sap in buckets. Plastic tubes run into and between trees, depositing collective sap in storage tanks. Tubes could be placed before snowfall, allowing Canadians to collect the sap—the depth of the snow was no longer a deterrent.
“It takes 40 gallons of sap to make 1 gallon of syrup, with each tree producing about 10 gallons annually,” said George Cook, farm safety and maple specialist at the University of Vermont Extension Maple Program. “Nobody wants to dig out that many trees in the middle of winter.”
By the 1970s Canada replaced the United States as the major producer of maple syrup because of tubing, lower production costs, and government subsidies. According to the Quebec Statistics Bureau and the U.S. Department of Agriculture, Canada produces 80 percent of the 6 million gallons of maple syrup produced each year worldwide; the United States produces the remaining 20 percent. Though maple trees grow in cool climates throughout the world, sugar maple populations grow only in Northeastern North America. Vermont is the primary American producer, followed by New York and Maine. Though the industry is not large, the USDA calculates that in Vermont alone, maple syrup brings in more than $10 million annually and provides 4,000 jobs, a significant contribution in a state of about 600,000 inhabitants.
In the last few years, many maple syrup producers say they have been seeing more variability in the amount of sap their trees produce and that overall production is down 10 percent. “It is more the quantity of syrup that is declining and not so much the quality,” said Barry Rock, a professor of natural resources at the University of New Hampshire. Ideal sap conditions are long, cold winters followed by a series of freezing nights and warm days in the 40s that allow sap to flow. The highest quality sap, meaning highest sugar content, is produced in the first flow of the season.
“Maybe it’s climate change. Year before last and ’97/’98 there wasn’t enough freezing,” said maple producer Richard Atwood. “Production was maybe 25 percent less then.”
Erin Bragg, of the Bragg Farm, Sugar House and Gift Shop in Vermont, agreed. “You have to have the right weather pattern for sap to run. It’s very variable, and you can’t follow the calendar anymore to know when the first flow will be,” she said.
Traditionally, the sap flow went from late February through April, and while most producers point out that it has always been somewhat erratic, they agree that variability seems to be increasing. “Climate change hasn’t seemed to affect it (the sap run) yet, but we’ve already seen warmer temperatures,” Bragg said.
Since temperature recordkeeping began in 1880, four of the warmest years occurred in the past decade (1998, 2002, 2003 and 2004), according to the National Climatic Data Center. The New England and New York region has warmed by 0.7 degrees, with most of the warming occurring since 1976. Researchers project that the largest change will be seen in winter, the crucial season for sap production, and that by the end of the century winter night temperatures will rise an additional 4–9 degrees. Professor Barry Rock, also a project coordinator for the New England Regional Assessment of the Potential Consequences of Climate Variability and Change, notes that several reasons unrelated to weather factored into the dramatic increase in Canadian production, however “10 percent of regional syrup production variability is now due to climate change, and it will only increase.” Warmer temperatures will affect other commodities too: apple crops will suffer, as will winter flounder and lobster populations.
Primarily as a result of burning fossil fuels, high levels of carbon dioxide (CO2) have been released into the atmosphere, causing heat to be trapped near the earth’s surface—resulting in higher temperatures—generally accepted as the cause of climate change. In a 2000 report, the U.S. Global Change Research Program estimated that within the next century, the type of trees that comprise many northeastern forests will change. “It’s going to be a competitive balance between the northern hardwoods and oak/hickory,” said Timothy Perkins, director of Proctor Maple Research Center at the University of Vermont. “It’s more difficult for maple/beech to reproduce in warmer temperatures. Oaks and hickories reproduce better.”
Although most projections about the shifts in forests come from computer models, researchers are also contributing experimental evidence. In an upcoming study in New Phytologist—a journal devoted to the study of plants—David Karnosky, professor of forest resources and environmental science at Michigan Technological University, examined the impact of atmospheric changes, not temperature. He looked at increased CO2 and ozone—another greenhouse gas that is growing in concentration near the earth’s surface—on a grove of sugar maple seedlings for five years to see how they would fare in conditions of global warming. Typically, plants thrive on higher CO2 but are stunted by ozone; taken together, the two gases seem to have a balancing effect on most plants. But Karnosky found that sugar maples do not react like most plants.
“The maple does not respond positively, it does not look good for the maple,” Karnosky said. “We didn’t detect a significant decrease in growth with just ozone and there was little response to high levels of CO2. The most negative treatment after five years was the combination of CO2 and ozone.” The seedlings that were exposed to high levels of both gases were severely stunted.
Maple specialist George Cook responded pragmatically to the study. “We’re not of the doom and gloom school. We’ll do research. We’ll adapt. We’ve got time and we’re already started."
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