We conducted a web search for “Global Warming and Maple Syrup” and found over 150,000 sites – almost all proclaim that the maple syrup industry is in deep peril given the threat of global warming. This must surely be seen as bad news for all those who enjoy maple syrup on waffles, pancakes, oatmeal, crumpets, and French toast (and in any number of desserts as well). Before you think this threat is less than serious, be aware that maple syrup is big business in New England and in Canada.
But, as with most things you read about on the majority of websites, the fate of maple syrup turns out to be not nearly as bad as portrayed. In fact, the future may be even better for maple syrup production than the past.
In case you do not know, maple syrup is a sweetener made from the sap of sugar maple or black maple trees. In cold climate areas, these trees store starch in their stems and roots before the winter, which when converted to sugar, rises in the sap in the spring. Maple trees can be tapped and the sap is collected and concentrated.
Vermont is the biggest U.S. producer, with nearly a million gallons of syrup produced annually. Maine produces about a third of that amount annually; New York, Wisconsin, Ohio, New Hampshire, Michigan, Pennsylvania, Massachusetts, and Connecticut all produced marketable quantities of maple syrup as well. While the U.S. production of maple syrup is significant, Canada produces 80% of the world’s maple syrup with most production occurring in Quebec.
Production is concentrated in February, March, and April, depending on local weather conditions. Freezing nights and warm days are needed to induce sap flows. The change in temperature from above to below freezing causes water uptake from the soil, and temperatures above freezing cause a stem pressure to develop, which, along with gravity, causes sap to flow out of tapholes or other wounds in the stem or branches. You immediately see that sap is dependent on climate conditions, predicted changes in local and regional climate can be linked to the production of maple syrup, and according to thousands of websites—and U.S. government climate impact reports—climate change will surely be bad for syrup production, at least in New England.
Our interest in maple syrup and climate change was related to a recent article in the peer-reviewed journal Climatic Change produced by three scientists at Cornell University; the work was supported financially by the New York State Agricultural Experiment Station and by the National Oceanic and Atmospheric Administration. In the beginning of their article, Skinner et al. review the literature on climate change and maple syrup and indeed there are articles in the professional literature suggesting a decline in sap production given any warming in the critical winter months. However, others found “significant increases in sapflow days for three Quebec stations, non-significant trends for other Canadian stations and non-significant decreases for the two Vermont stations” over the most recent four decades. Once again, there is a debate in the literature – this time, the debate is on whether or not warming will have a positive or negative impact on maple syrup production.
Skinner et al. used a detailed 30-year record of sapflow and weather observations from the Uihlein Forest near Lake Placid, New York to develop and test a numerical model linking sapflow to local weather observations. They also gathered high-resolution daily maximum and minimum temperature data that were interpolated to a 5 × 5 kilometer grid; these records were used for downscaling more course temperature predictions from three general circulation models predicting climate effects of the ongoing buildup of greenhouse gases.
Skinner et al. note that “The major finding is that sap collectors will need to get busy earlier in the late winter and spring to adapt to the expected warming winters in the New England states. Through the twenty-first century, the optimal time to maximize sapflow days will advance to an earlier date in the year. By 2100 this change will be nearly 30 days.” They further note “Provided the change in the beginning of the sapflow window can be anticipated, the number of sapflow days will change very little through 2100 in the heart of the Northeast U.S. maple syrup production region. In fact, across Maine, the simulations show an increase in the number of sapflow days provided the 8-week window is moved to early February.” If you are worried that sap producers will be forced to cope with increased climate variability, relax, as Skinner et al. conclude “There is no indication that the year-to-year variability in the number of sapflow days will change substantially through the current century. Current year-to-year variation is a substantial challenge for maple producers; it shouldn’t worsen.”
They state “by moving the tapping window a month earlier across northern New York and New England, the number of sapflow days in 2100 will be no different (or even slightly higher) than what is experienced today.” They also reinforce their conclusion on variability stating “The year-to-year variability in the number of sapflow days does not change appreciably during the twenty-first century based on the model projections. This suggests that the challenge that interannual variations in sapflow days presents to maple producers may not be exacerbated by climate change.”
If you are concerned about what is happening in Canada, be aware that the authors conclude “the U.S-centric results provide some insights into the changes that are likely to occur under climate change in this area. Currently maple syrup production in Quebec exceeds that of the United States. In this region, based on the models analyzed, it is reasonable to assume that by adapting to climate change by moving the conventional tapping period, the number of sapflow days can be maintained at present day levels. The number of flow days might even increase slightly in this colder climate as is projected to occur in parts of Maine, provided factors such as tree health and disturbance frequency (e.g. ice storm damage) remain unchanged.”
Their final sentence says it all as they conclude:
Thus, overall it appears that a relatively minor change in current maple sugaring operations has the potential to maintain sapflow at current-day levels despite the warming that is anticipated to occur during the twenty-first century.
Contrast this with the government’s assessment of the situation, as presented in the report Global Climate Change Impacts in the U.S.: New England:
Agricultural production, including dairy, fruit, and maple syrup, are likely to be adversely affected as favorable climates shift.
Looks like things are in need of an update.
We won’t be holding our breath.
Skinner, C.B., A.T. DeGaetano, and B.F. Chabot. 2010. Implications of twenty-first century climate change on Northeastern United States maple syrup production: Impacts and adaptations. Climatic Change, 100, 685-702.