By Michael J. Caduto
Walking through the woods recently, I noticed a rusty sap bucket hanging from an old maple tree on a tap that had probably been forgotten some fifteen years ago. The bucket, which had originally been placed about four feet off the ground, was now ten feet high, having moved up as the tree grew. The maple was the biggest tree in sight, so it had to be the oldest.
I thought about how springtime was arriving earlier now because of global warming, and so farmers must be experiencing a longer season in which to make more maple syrup. Then I wondered if the way that climate change is impacting the hole in the ozone layer would hurt the trees. “And we must have solved the problem of acid rain,” I thought, “because I never hear anything about it anymore.”
Along the way, I passed a fallen tree and contemplated how it must have landed silently because no one had been there to hear it.
When I got home I walked through the door and into the mudroom. I looked at the calendar and noticed the date: April 1. Then I heard the alarm go off, and I woke up.
April Fools! This imaginary dream spins some common misbeliefs about nature and the environment. Here are descriptions of the myths, followed by the corresponding truths.
A nail driven into a tree moves up as the tree grows. Trees only grow upward from the tips of the branches. A nail or sugaring tap driven or drilled into the side of a tree will remain at the same height over time. The bole, or trunk, of a tree grows outward, so eventually the nail or hole will be engulfed by wood.
The biggest trees are the oldest trees. Growth rate depends on a combination of genes and growing conditions. Some species (white pine, cottonwood) grow quickly, while others (white oak, hickory) grow more slowly. A 50-year-old red oak that is growing in fertile soil with plenty of sunlight might be 16 inches in diameter, while a red oak of similar age that is competing with other trees in poor growing conditions might be only 10 inches across. A shagbark hickory of the same size, growing nearby, could be 75 years old.
The earlier arrival of springtime due to climate change will enable farmers to make more maple syrup. Climate change impacts the timing and duration of maple syrup season, as well as the sugar content of sap. Research published in Forest Ecology and Management (2019) reports that sugaring season in eastern North America is becoming shorter, starting sooner and could occur one month earlier by the end of this century. Data from the U.S. Historical Climatology Network shows that the mean annual global temperature has risen by 3.8 degrees Fahrenheit since 1835, but that 70 percent of this increase has occurred since 1970. Research conducted by the University of New Hampshire revealed a striking parallel: the sugar content of sap has dropped nearly 30 percent since the 1970s. While modern technologies, such as Reverse Osmosis, have enabled maple sugar-makers to increase the volume of syrup produced, the sap-to-syrup ratio has declined. In the 1970’s it took 25 to 30 gallons of raw sap to make 1 gallon of syrup. Nowadays, however, during a good year, some 45 to 50 gallons of sap would need to be boiled off to produce the same yield.
Climate change is causing the hole in the ozone layer in the upper atmosphere. Not so. The thinning of the ozone layer in the upper atmosphere over the Polar Regions occurs during springtime and has been most severe in the Antarctic. This phenomenon was caused by the widespread use of chlorofluorocarbons (CFCs)—gases used as refrigerants and propellants. Although CFCs were banned globally in 1987, it is taking decades for the ozone layer to recover. While depletion of the ozone layer is not caused by global warming (although there are some related interactions), the success of the 1987 Montreal Protocol on Substances that Deplete the Ozone Layer demonstrates that nations of the world can act together to solve long-term atmospheric problems. Research reported by NASA in 2018 revealed that declines in atmospheric levels of CFCs have meant that ozone depletion during Antarctic winters had decreased by 20 percent since 2005. It is estimated that the ozone layer in the Arctic will heal by around 2035, and in the Antarctic by about 2060.
The problem of acid rain has been solved. The problem of acid rain in North America has been mitigated, but not eliminated. Pollution controls required under the 1990 amendments to the Clean Air Act decreased the emissions of nitrogen oxides and sulfur dioxide from vehicles and power plants. Overall, sulfur dioxide levels have fallen more than 93%, and emissions of nitrogen oxides have dropped over 86%. Still, it is taking time for soils, plants and aquatic ecosystems to recover from the impacts of acid rain. And acid rain remains a major problem in some countries, such as India and China, whose emissions also exacerbate acid rain in South Korea and Japan.
If a tree falls in a forest and there is no one around to hear, it makes no sound. Maybe. Maybe not. You’re on your own for this one.
Curt Allen—Farm Director for Spring Brook Farm in Reading, VT—checks settings on the Reverse Osmosis (RO) machine that removes water from maple sap. With exceptionally warm weather in March of 2021, sugar content in tree sap has been low at 1.5%, but the RO machine concentrates this to 8% sugar before the sap enters the evaporator. This process saves the farm some 75% on staff time and fuel while boiling sap down to maple syrup. Photo credit: Michael J. Caduto
The evaporator for boiling sap into maple syrup at Spring Brook Farm. Photo credit: Michael J. Caduto
Portions of this article adapted with permission from Through a Naturalist’s Eyes: Exploring the Nature of New England by Michael J. Caduto.