Maple trees have long been a staple of Northeastern America, valued for both aesthetic and practical purposes, including their ability to produce sap that can be turned into an edible syrup, first produced by Native Americans. On the surface, this process seems to be holding steadfast in the face of climate change as maple syrup production increases by 10% each year due to new developments in sap collecting mechanisms. But looking into the future, is this industry sustainable?
Maple syrup is extracted from sugar, black, or red maple trees that convert stored starch in their trunks to sugar that accumulates in the sap. By drilling holes into maple trees, sap is collected and then boiled to evaporate excess water. This sap must be collected in early Spring due to the freezing and thawing cycles necessary for sap flow. Maple syrup is classified as Grade A or B depending on how dark it is, with darker syrups extracted later in the season. Although it contains a large amount of sugar, maple syrup is also a good source of vitamins and minerals such as manganese, calcium and zinc.
Maple forests themselves are ecological powerhouses due to their carbon trapping and storing abilities. Maine’s 7.2 million acres of forest (maple, beech and birch) store 550 million metric tons of carbon. In Vermont, half of the state’s emissions are absorbed by forests. These forests are protected by the maple industry’s need for them. Maple syrup serves as an environmentally friendly alternative to white sugar, as it is not made from animal products. Additionally, well-tended trees can produce sap for over 100 years, so it is a very sustainable practice, although the same cannot quite be said about the industry as a whole.
Unfortunately, but perhaps not shockingly, changing seasons are already resulting in a detrimental effect on the maple syrup industry. According to the University of Vermont, the average sugaring season begins 8.3 days earlier and ends 11.6 days earlier than fifty years ago. This change is accelerating — by 2100, the sugaring season is expected to begin an entire month earlier than in 2050, reducing syrup production even further. The cycles of early spring freezing and thawing are the key components behind sap flow, but more intense weather patterns have resulted in a disturbance of these cycles. In addition, global warming causes daily low temperatures to increase more often, making the freeze-thaw cycles less extreme. Maple trees also rely on snow accumulation to insulate heat and protect roots from freezing. As overall snow production in the Northeast decreases, this could also serve as an obstacle for the maple syrup industry. Although 21st century Vermont has made a booming recovery in maple syrup production, with the state’s maple industry value exceeding $54.3 million, these increased cycle spikes and rising temperatures threaten to reverse this recovery.
A 2019 study at Dartmouth College found that the range of syrup production will be further decreased in the future as states such as Virginia and Indiana would barely be able to produce any sap due to warmer temperatures, while production in cooler areas such as Quebec will be increased. However, as the climate continues to warm, increased production probably will not last even in Quebec. The industry may not be able to simply shift further north since it is limited by the soil chemistry and fungi of northern soils. Sugar content in sap is also estimated to decrease by 28-36% as trees will likely not be able to store carbohydrates at the same level.
Increased invasive species numbers are also playing a role in the decline of maple trees. Earthworms, which are native to Europe and Asia, have been contributing to the decline of sugar maples since their roots are close to the forest litter which is eaten by earthworms. Additionally, native forest tent caterpillars have been found to lay eggs in maples, leading to their defoliation and to lower sugar concentrations in their syrup, which was amplified by a drought in Vermont in 2017.
There have been some efforts designed to mitigate these changes. In 2019, USDA announced there was $4 million available in grants to support the maple syrup industry through the Access and Development Program (Acer), including sanitation of the tap hole on the tree to keep it healthier for longer. More complex sap collection technology also allows for syrup with lower sugar content to be more profitable and easily extracted. This process is accomplished through reverse osmosis technology, which uses a membrane to separate water and sugar, leaving behind higher sugar content sap that speeds up the boiling process. But with an increase in frequency of extreme weather events, decreased snowfall, and soil chemistry preventing range shifts in the face of warmer temperatures, will this be enough to keep the industry alive? Only time will tell.
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