Maple syrup, a common breakfast condiment, is produced by concentrating the sap of the sugar maple, Acer saccharum. In early spring, forests of sugar maple, Wisconsin’s state tree, are tapped by the hundreds at many commercial and family-run "sugarbushes,” or wooded areas managed for maple syrup production, across the state. Many family farms in Wisconsin and elsewhere across northeastern states and eastern Canada, produce maple syrup for extra income, gifts, or family use. Considering that many producers are family-run businesses that have been producing syrup for up to four generations, maple syrup production undoubtedly has an important cultural significance in Wisconsin. Even small-scale non-commercial sugarbushes involve many people, often extended family or close friends, in the collection and boiling of sap. In many school districts in northern Wisconsin, students are taken to local sugarbushes to learn how to collect and process sap. In addition, the Ojibwe of Wisconsin have harvested sap for cultural subsistence for centuries.
Maple syrup production also has an economic impact in Wisconsin. According to the National Agriculture Statistics Service, Wisconsin is currently the number four maple syrup producing state. Additionally, the crop value for just over 500 producers was roughly $5,865,000, in 2008 alone. In 2009, those 500 plus producers managed over 670,000 taps and produced over 200,000 gallons of maple syrup (keep in mind it takes approximately 40 gallons of sap to produce one gallon of syrup).
Any family who runs a sugarbush can tell you that weather plays a critical role in the production of maple syrup. Although little scientific research has been done, producers will argue that temperature variation, fall soil moisture, wind, spring soil moisture, or humidity can impact a sugarbush’s success. The best conditions for sugaring are cool nights, just below freezing, and fairly warm days, in the upper 40s °F. This temperature change causes shifts in pressure outside the tree that send sap flowing throughout the tree and out any open wounds, like a hole for a tap. The National Agriculture Statistical Service data shows that in 2005 and 2007, the number of gallons of syrup produced in the state of Wisconsin was very low. Years of poor production are most often tied directly to environmental conditions. Considering the fact that maple syrup production happens over the period of about one month and is weather dependent, changes in climate could have significant impacts on the statewide production of maple syrup.
Sugar maples are usually found in moist and nutrient rich environments and are more common in northeastern states. Researchers at the University of Wisconsin-Madison have used climate models to predict the future distributions of the sugar maple and have found that it is expected to reduce in abundance in Wisconsin. Gradually, we can expect that sugar maples will become more stressed and prone to insect damage as state average temperatures, especially as winter temperatures continue to increase.
Researchers have also downscaled global climate models using local historical climate data to generate fine-scale climate change predictions statewide. From this data we can anticipate potential climate change impacts on maple syrup production. The data indicates that we can expect: a 4.5 to 6 °F increase in average spring temperatures, with a 4.2 to 6.3 °F in average spring highs and a 4.5 to 6.3 °F increase in average spring lows. Furthermore, they project the last spring freeze will come 12 to 15 days earlier, a 7.5 to 12.5 days earlier onset of springtime conditions, a slightly wetter fall, a wetter spring, and a reduction in the probability of frozen precipitation (e.g. snow) in March. Also, we can anticipate a 14 to 18% reduction in the frequency of cold days (≤ 20°F) for northern Wisconsin and a 10 to 12% reduction for southern Wisconsin. Based on this data we can expect the maple syrup season to begin and end earlier in the year, and a reduction in the number of cold days could reduce the season length. However, without scientific research we can only infer how other climatic variables could influence maple syrup production.
Therefore, we can only speculate that the decrease in the probability of snow and a slight increase in spring and fall precipitation could have negligible or even positive impacts. However, it should be pointed out that the potential benefit from slight increases in precipitation in spring and fall could be outweighed by greater evaporation caused by high temperatures and low precipitation during the summer. Also, warm daily temperatures following periods of high sap production can cause sap to sour before it can be processed. Finally, the responses of the local climate to regional climate change could impact wind speed, frequency, and direction, which are all considered to be important factors in maple syrup production.
- Wisconsin Model Academic Standards for Science: This resource aligns with Science Applications Standard G.12.4 and Science in Social and Personal Perspectives Standards H.4.3, H.8.3, H.12.4