MIDDLEBURY — This past Saturday, over 100 sugarmakers gathered at Middlebury Union High School to hear presentations about the state of the maple industry, talk shop and enjoy some delicious maple doughnuts at the annual Addison County Maple Sugarmakers Association (ACMSMA) Maple Seminar.
Although presenters noted in the opening address that the maple industry is pretty stable at the moment, some audience members had one serious concern: climate change.
“Global warming has definitely affected (the sugaring season),” said ACMSMA President Moe Rheaume.
The future of maple in the Green Mountain State is critically important not just to sugarmakers but also to most residents of the state. Vermont’s maple industry brought in $54.3 million in 2018, the largest  amount of any state, according to the USDA. And the maple tree, boiling sap and sweet syrup are iconic features of the state’s landscape, history and culture.
Rheaume, a Salisbury resident who has been in the maple business almost 50 years, is among many local sugarmakers who fear that the warming temperatures, severe storms and invasive species caused by global warming will destabilize the maple industry.
Vermont is one of the fastest-warming areas in the country, according to a 2017 report by research institute Climate Central. The Environmental Protection Agency also warns that the state has warmed by more than 2 degrees Fahrenheit in the past century.
Although 70-degree days remain an anomaly, there’s no doubt that Vermonters are experiencing warmer winters than ever before. In 2017, Climate Central reported that the average winter temperature in Burlington had increased by seven degrees Fahrenheit since 1970.
Warming temperatures lead to rainier springs, drier summers, and more severe storms as the seasons change. Strong winds can severely damage maple trees or knock down tubing, and a warmer climate also makes Vermont a more hospitable home for destructive invasive species such as the Asian long-horned beetle and the tent caterpillar.
“Global warming, warming temperatures and the pests” are most critical threats to the maple industry,” Rheaume said. “The Asian long-horned beetle is the biggest threat.”
Another concern is that Vermont’s iconic winters are becoming shorter and warmer, forcing sugarmakers to contemplate a new and uncertain future for their business.
“It’s not unheard of to have warm weather in January,” said Mark Isselhardt, UVM Extension’s Maple Specialist. However, “one of the risks we are concerned about… is more anomalous high temperature events.”
Isselhardt cited a series of warm days in March 2012 — at the start of the traditional sugaring season — where temperatures reached into the 70s. High temperatures can pose a serious problem for sugarmakers, as warm weather affects sap quality and helps microorganisms in tapholes and tubing grow, shutting down the flow of sap.

HOW SAP FLOWS
The state’s warming climate is already bringing about a major change in many sugaring operations.
Maple sugaring requires a series of freeze-thaw cycles where the temperature dips into the 20s Fahrenheit at night and up to the 40s during the day, which builds pressure within the tree and causes the maple sap to flow. These freeze-thaw cycles used to be common in March and April, but with the early onset of warmer spring weather they are increasingly happening earlier in the winter.
“Years ago, everybody started tapping on Town Meeting Day,” said Don Gale, who owns Twin Maples Sugarworks in Lincoln.
These days, some sugarmakers with large operations of more than 50,000 taps are tapping their trees in January or even early December, just to get the taps in before sugaring starts in earnest.
“The big onset of sap flow is happening earlier,” Isselhardt explained. But while an extended period to collect sap may seem like a good thing, both he and Gale agree that warming winters only add to the uncertainty sugarmakers face. Although sap starts to flow earlier in the winter, it’s much less reliable than in previous years.
“We had our last boil actually in May (two years ago),” Gale said. “Last year we tapped at the same time and got nothing, not even a drop of sap.”
The earlier and earlier start of the sugaring season makes it difficult for sugarmakers to predict when to start tapping trees, and causes more variation in the freeze-thaw cycles they rely on. An unpredictable climate means fluctuation in the amount of sap sugarmakers can collect, and therefore the amount of syrup they can produce.

LONG-TERM PROBLEM
Although sugarmakers are doing all they can to mitigate the fluctuations in temperature and sap flow, earlier sugaring seasons may be only a symptom of a larger, long-term problem.
Due to Vermont’s warming climate, the ideal habitat for maple trees to grow is moving northwards into Canada. If global warming continues at its current rate, Vermont’s winters will eventually be too warm for the crucial freeze-thaw cycles, and too warm for maple sugaring.
“We’re really good at tactics to overcome early onset of spring, but eventually it will become overwhelming, I think, when we have the climate of New Jersey or Virginia,” said Dave Folino.
Folino, who owns Hillsboro Sugarworks in Starksboro, worries that despite sugarmakers’ best efforts, their livelihood is ultimately incompatible with the warming climate.
UVM’s Isselhardt is also concerned that the fussy sugar maple will one day find Vermont an unsuitable habitat, but he says that as long as sugarmakers continue to practice sustainable “active management” of their lands, that day is a long ways off.
For now, sugarmakers seem to be coping pretty well with the changing climate, adapting their practices to take as much advantage as possible of the earlier sugaring season and new technology.
Area syrup producers are doing all they can to increase sap yield and stabilize production by implementing new tapping and collecting techniques. For example, using a vacuum pump to draw sap from the trees and leaving spouts in the trees for longer periods of time to prevent the tapholes from closing ensures that as much sap as possible is harvested from each tree. Reverse osmosis machines remove water from the maple sap before it’s boiled, cutting down on boiling time and reducing fuel usage.
“Some of that technology has mitigated” the uncertainty an earlier season brings, Isselhardt said.
Although sugarmakers agree they can see no benefits to climate change, many are choosing to stay positive and focus on adapting to our newer, warmer winters rather than simply waiting for the worst.
“(Climate change) is not really affecting crops yet,” Folino said, “because we’re able to tweak and adjust.”
Hopefully Addison County’s sugarmakers will be able to continue tweaking, adjusting, and adapting their practices to ensure a healthy maple industry for many years to come. But some day, the future will be here.
“Right now, and for the last 50 years, we’ve been in the ideal spot on the globe (for sugaring),” he said. “But that ‘sweet spot’ is moving north.”