Peter McCluskey is clearly proud of his handiwork. Standing on a forested slope in Wisconsin’s Driftless Area, he describes the complex network of wet-dry lines, laterals, valves, and vacuum pumps that helps him and his family pull thousands of gallons of sap out of their maple trees every spring.
Translucent blue plastic tubes weave between and around the smooth-barked trees. Valves and fittings send smaller lines perpendicularly from the main line to individual trees, where they culminate in taps. “It looks like a big spider web,” McCluskey says.
Five generations of McCluskeys have farmed dairy cows in the hills and valleys of western Wisconsin, but they only decided to go commercial with maple syrup in 2009. With the help of a reverse osmosis filter the size of an industrial refrigerator and an even larger apparatus known as a steam-away machine, the McCluskeys can process thousands of gallons of sugar maple sap in a few hours. Last year they boiled over 40,000 gallons of sap down to 500 gallons of syrup and sold most of it at area farmers markets and to local restaurants.
This year, though, production was down by half. A sudden spell of sustained warm weather in March drastically shortened the window during which the state’s maples produced high-quality sap. The unseasonable temperatures caused multiple problems, Peter explains.
“Ideally what we’d like to do is get mid 40s and sunny during the day, and 20s at night. That sends the sap up the tree during the day and back down and night, and prolongs the trees from flowering. This year it sits at 70 for two weeks, the trees aren’t going to stay dormant, they’re going to say ‘oh it’s time to grow,’ and we have a short season.”
In addition, Peter’s uncle Brian explains, the warm weather happened so fast that some of the sap actually fermented in its holding tank before they were able to process it.
Eric Kruger, a tree physiologist at the University of Wisconsin-Madison, explains why maples need alternating above-freezing days and below-freezing nights for sustained sap production. “When the water in the stem freezes at night, that creates a physical suction that will draw water from soil through the roots into that region of frozen water. Frozen water attracts water. So in order for the trees to stay pressurized, there has to be water drawn up to replace the water that’s been tapped.
“It happens solely when it’s freezing.”
While the McCluskeys have taken a hit this year, others in the state have fared worse. Gretchen Grape, the executive director of the Wisconsin Maple Syrup Producers Association, told a Milwaukee Journal Sentinel reporter that it was the worst year she and her husband could remember for maple syrup. Other Wisconsin producers only made enough syrup for personal consumption.
Unfortunately for these producers, warm winters and early springs may soon be the new normal. Winter is the season that is predicted to warm the most due to climate change in Wisconsin, according to the Wisconsin Initiative on Climate Change Impacts, a partnership between University of Wisconsin and the Wisconsin Department of Natural Resources. The organization’s 2011 report forecasts average winter temperature increases of 7.5 to 9 degrees Fahrenheit between 1980 and 2055. Beyond simple warming, increased weather volatility will also make things less predictable for producers on a year-to-year basis.
Wisconsin’s maple sugar producers contribute only a tiny fraction of the state’s $60 billion a year agriculture industry, and few of them rely solely on syrup for their income. But they do represent an economy and a tradition that goes back farther than almost any other agriculture practice in the state, according to the Wisconsin Historical Society. Native Americans tapped maple trees before Europeans arrived in Wisconsin, and immigrants from New England and New York brought the practice with them. Enough warming, however, and this tradition could be lost.
For the McCluskeys, though, the forecasts of warming aren’t an immediate concern. They have some syrup left over from last year that they hope will plug this year’s gap.
In fact, they don’t even plan to raise their price. “We have a pretty good customer base and we don’t want to change that,” says Peter.
And in the end, they acknowledge they have limited control over what the trees give them.
Standing in his family’s maple forest, Peter reminds me, “Mother Nature’s in charge, not you.”