BRATTLEBORO — “When my daughter was young, we would say to her, when the leaves seemed to turn color overnight, 'How did you do that? Did you paint those trees?' And we would all laugh,” says Lynn Levine, a local forester and environmental educator.
Autumn's color changes do seem magical: what yesterday was just a lot of green “suddenly” is a polychromatic display, as if overnight. Gold, russet, orange, red, and purple fill hilltops and roadsides.
Of course, it doesn't really happen overnight, and there's nothing paranormal about it. The color changes slowly, sometimes escaping our notice until it's too vibrant to deny: summer is over; autumn is here. And science explains it.
Levine describes trees as “smart.” A smart organism evolves strategies for longevity and reproduction. And conserving energy is key for a tree to survive our cold winters.
It is an energy loss for trees to keep their leaves in winter, Levine says. “So, when the days get shorter and the temperature colder, the leaves stop producing chlorophyll (the green substance) which, combined with CO2, makes sugar, which is necessary for tree growth.”
She says that the green of the chlorophyll in leaves masks their other inherent colors, such as yellow and orange: “Most trees lose the chlorophyll, but trees like the red maple make new sugars that make the leaves red. So we're left with a wealth of colors.”
This process is not merely theory. Aberrant weather allows us to see science in action.
The early ice storm of 2012 demonstrates what would happen to our forests in winter if the deciduous trees didn't shed their leaves in autumn, explains Levine. “The storm caused branches, still laden with leaves, to break, and entire tops of mature trees to snap off.” She adds: this obviously harms the trees.
Seasons aren't the only variation to which trees must adapt: Climate change may also affect our annual foliage display.
Each species of tree has a spatial range in which it grows, Levine says. “Where we live, in Windham County, we have a great mix of species, a mix of species that grow in warmer climates (e.g. the oaks), and those that live in colder climates (e.g. white birch).
“It is most probable, according to most forest researchers, that sugar maple will gradually march north, and out of our region, and that means we will miss their magnificent orange color. More oaks will move north into our area, which means that we will have more reddish brown. How long will this take? Only time will tell.”
Enjoy it while you can.