Brownout? Vt. maples feel the heat of climate change
Jeb Wallace-Brodeur / Staff photo
Vermont researchers say climate change is threatening fall foliage — like this maple leaf — and spring sugaring.
Editor’s note: Five years ago, this paper explored recent climate shifts in a set of reports titled “Vermont’s Changing Seasons.” This story is part of a monthly series of updates.
By Kevin O’Connor
Plant physiologist Thomas Vogelmann savors autumn’s fiery colors. But lately he’s spotting — and lamenting — a more searing change.
The 60-year-old was just a boy when, tagging along, he began following in the footsteps of his father, Hubert “Hub” Vogelmann, the University of Vermont botany professor who launched the school’s groundbreaking studies of the woodlands that cover three-quarters of the state.
Maples, Tom learned, make up one of every four trees. Each spring, their sap earns Vermont $200 million in total economic impact as the nation’s largest producer of syrup. Each fall, their red, yellow and orange foliage is pure gold to leaf-peepers, loggers and other locals tied to the state’s nearly $1.5 billion forest-related manufacturing, tourism and recreation economy.
Vogelmann, now dean of the university’s College of Agriculture and Life Sciences, is helping carry on his father’s work. But he and his peers in the school’s Plant Biology Department and Proctor Maple Research Center say rising temperatures are shrinking the length of the sugaring season and threatening to supplant the flaming hues of traditional trees with blander, browner Southern species.
“All these studies are pointing to the fact that things are shifting,” Vogelmann says, “and faster than we had anticipated.”
The term “global warming” had yet to be coined in 1964 when Vogelmann’s father began investigating how vegetation varied at different altitudes on Camel’s Hump, the state’s most celebrated mountain (its silhouette is minted on 883 million quarters) and tallest undeveloped peak.
Hub Vogelmann wanted to learn what climatic and soil changes were favoring maples at the lower elevation and spruce and fir at the higher reaches. Some of his superiors didn’t see the value of such study. But the professor and his students went on to find a precipitous decline over time in nine species of trees, including sugar maples, beech, white birch and, most notably, red spruce.
Some blamed insects, plant disease, poor soil or abnormal weather. But the elder Vogelmann believed the signs pointed to pollution, noting that Midwestern clouds drifting over Camel’s Hump dripped with industrial chemicals and metals such as cadmium, copper and lead.
Thirty years ago, the professor made news by sharing his findings in a Natural History magazine article titled “Catastrophe on Camel’s Hump.” The 1982 story — one of the first mainstream explanations of the effects of acid rain — sparked the interest of mass-market publications like Time and, soon after, everyone from Congress to the common man.
Hub retired in 1991; son Tom became the school’s botany chairman in 2002 and dean in 2008. The university still monitors the mountain. But acid rain no longer is its biggest concern — climate change is.
At least one or two hard frosts must hit each fall to kill the chlorophyll that keep leaves green in the spring and summer. For Columbus Day visitors, that means foliage won’t blaze on cue if autumn’s chill arrives late. More significantly, warmer temperatures over time threaten to supplant the bonfire colors of maple, beech and birch with a habitat more conducive to flatter-hued oak and hickory.
Working with associate professor Brian Beckage, students have tracked hardwoods such as sugar maples in the lower elevations and conifers including spruce and balsam fir in the higher ones. Reviewing almost a half-century of findings, they have discovered the conifer zone has retreated 70 to 120 meters upslope. That distance — about the length of a football field — equals 8 percent of the peak’s elevation.
Scientists worry that’s just the start. The state’s average winter temperature has warmed about 1 degree in each of the past five decades — a trend projected to continue if the world’s greenhouse gas emissions remain consistent.
“If Vermont does get as warm as Virginia,” Tom Vogelmann says, “the forest composition will be different.”
That’s because warmer weather abets not only Southern species but also tree-killing insects, diseases and droughts. Maple, beech and birch make up almost half of the Northeast’s commercial timberland. But the U.S. Forest Service projects that oak and hickory, which now comprise less than 15 percent of Vermont woods, could overshadow traditional trees by the end of the century.
Rising temperatures already are shrinking the annual sugaring season that reaps Vermont some $20 million in sales and more than 10 times that amount in related economic and employment impact.
Timothy Perkins has experienced the shift firsthand. As a child, the 51-year-old Northeast Kingdom native lugged pails of sap into his grandfather’s sugarhouse. As a student, he studied trees alongside Hub Vogelmann. And as current director of the Proctor Maple Research Center — the oldest and largest such facility in the world — he and his colleagues test the technology that has replaced the buckets of his youth.
The science of maple syrup is rooted in a few simple facts: A tree contains sap. When the temperature rises from a few degrees below freezing to a few degrees above, pressure builds up inside the trunk and pushes the sap out. To keep this process pumping, a tree must freeze and thaw repeatedly.
About 15 years ago, farmers began reporting that sap that used to flow after Vermont town meetings the first Tuesday in March was dripping as early as Valentine’s Day. Likewise, a sugaring season that once lasted four to six weeks was often ending four to five days earlier.
Producers questioned not only the shifting tapping period but also reduced sap flow and lower-grade product. Was climate change the reason and, if so, what might it mean for the future?
A decade ago, the center launched the first regional study of the “Effects of Global Change on the Maple Sugaring Industry.” Researchers asked sugarmakers in New England and New York for their production records over the last four decades and then culled the data for any significant shifts.
The findings: The sugaring season is starting more than a week earlier than it did nearly a half-century ago, and its duration has decreased by an average of 10 percent, Perkins has testified to Congress.
Scientists aren’t surrendering. The center — boasting 2,800 maples on more than 200 acres in Underhill — is improving technology to help the state’s farmers tap every last drop.
Sugaring used to be as easy — and as hard — as hanging and hauling enough buckets to boil 40 gallons of sap down to one gallon of syrup. Today, producers can run plastic tubing from hundreds of trees to a sugarhouse, turn on a vacuum pump and a reverse-osmosis water-removal machine and watch their stainless-steel evaporator bubble with fancy-grade product.
To further heighten production, Perkins and his colleagues are studying tree health issues ranging from ground fertilization to air pollution. An average sugarmaker produces about a quart per tap a year. The center, through its testing of new techniques to collect sap more efficiently and condense it into syrup more economically, can squeeze out up to twice that amount.
“We’re trying to offset the shortened season by various means,” Perkins says.
But scientists are in the hot seat: This winter brought historic temperature highs.
“There’s a great deal of concern in the industry if this is something that’s going to repeat itself,” Perkins says. “This year was consistent with what we might expect given a warming climate.”
Exit the sugar maple, Vermont’s state tree?
“If you want a maple in your backyard, you’re going to have a maple in your backyard,” Perkins says. “The concern more is whether we’ll have the appropriate conditions to tap if the climate gets worse. If you can’t make enough syrup to support a viable commercial business, fewer and fewer people will.”
Researchers, however, can’t forecast the future. They can only continue to tap technology — and hold out hope.
“Weather and climate can really mix things up, and we can expect more,” Vogelmann says. “But we’re a resilient state. We will figure out a way to move forward.”