PETERSHAM, Mass.–In a small maple sugar shack in the Harvard Forest, Dr. Joshua Rapp is having a sweet Saturday. The adjunct professor is boiling maple sap into syrup on an unusually warm Mar. 5. It is the sticky side effect of his research on the effect of climate change on maple sap quality which received a two-year, $149,800 grant from the Northeast Climate Science Center.
“One thing we have found is that there are more phenolics in the sap the further south you go in the sugar maples’ range. That suggests that the warmer temperatures and the longer growing seasons experienced further south in the range may lead to a greater production of these phenolic compounds,” says Rapp.
Phenolics are the main class of chemical found in maple sap. They are a natural defense mechanism found in many plants that protects against invaders and imparts distinct flavors to our favorite foods.
“We have a grant from the Northeast Climate Science Center which is based at UMass, it is part of the [United States Geological Survey]. They fund research looking at natural and cultural systems and how they are affected by climate change,” says Rapp.
An increase of phenolics in the sap will create darker, stronger tasting syrup for local maple producers. Traditionally, darker syrups fetched less in the marketplace than lighter syrups.
“We look at maples, sugar maples particularly, as a cultural resource because not only are they part of the natural ecosystem but are highly beloved by humans not only for their spectacular fall color but for the maple syrup we can produce from them. The history of maple syrup goes back centuries to the Native Americans,”said Rapp.
The grant funds a collaborative field data collection effort from Virginia to Quebec. It also allows the researchers to conduct surveys on maple syrup producers. The researchers are utilizing data dating back to the civil war to locate trends in production.
At the Harvard Forest, Rapp conducts his research at the tap. He measures the weight of the sap, analyses the sugar content, and collects samples for phytochemical analysis. This data quantifies how production changes year to year.
Warmer temperatures mean a shorter tapping season for producers. This year’s sap collection began earlier and finished sooner than in previous years, with less yield. This means bad news for farmers looking to turn a profit.
Dr. Kevin McGarigal of the Department of Environmental Conservation at the University of Massachusetts says, “What can be done, other than obviously reversing the anthropogenic causes of climate change, is to protect, manage and restore habitat and populations to the extent feasible so that populations can be sustained for long enough to hopefully adapt.”
Next, Rapp says that he and the research team hope to conduct taste tests of syrups produced in different parts of the range in a controlled setting as a way to judge consumer preferences and how that preference correlates to the chemistry of the sap.