The fall leaves are changing...and not always for the good
October is here! It’s my custom at this time to remind you once again of the wondrous seasonal change now beginning and answer that burning question: Why do leaves fall off trees? To quote myself from past writings:
“With the tilt of the Earth, it’s clear that there will be less light for photosynthesis for food making, and water will be harder to get. Trees begin to shut down. At the base of each leaf is a small corky layer that swells and cuts off the flow of water. With no access to water, green chlorophyll disappears and we see the color of the leaves underneath. Eventually, the corky layer forms a disintegrating cell line that says ‘tear here’ and so each leaf falls to the ground. It’s a miraculous process.”
Now comes a new discovery: Researchers say red is not just hiding behind chlorophyll, like yellow and orange. Red is made from sugars in the tree as it prepares for winter. Around here we can expect an even mix of colors, but go to Vermont to see vibrant, glowing reds and red oranges due to the larger number of red and sugar maples.
Bright, dry months inhibit nitrogen uptake, thereby spurring sugars to synthesize red anthocyanin. Since we have had a lot of rain lately and cloudy skies with less light, we can’t expect bright reds this year in our area.
Besides rain and less daylight numerous other players are connected to this leaf dropping process in deciduous trees. Heat, freezes, smog, clouds, climate change and species sensitivities all play their parts in whether we have bright colors with many variations of yellow, red, orange, and brown.
There are timing factors, too. Do the leaves of the different species turn at the same time or set their own schedules according to their varied preferences? They each have their own timing. Look for tupelo/sourwood first to turn, then come dogwoods, maples, sweetgum, scarlet oak, and sassafras, followed by hickories, oaks, yellow poplars, birch and beech to name a few.
This used to happen quickly, but climate change has warmed up the planet so that there’s not the color peak there used to be, but rather a more drawn out season of drab colors. In fact, warmer temperatures and drought may convince trees to drop leaves even before they turn colors. Further, it’s all coming later.
Colors are starting at least two weeks later in October and likely will stretch through November. A warmer planet means duller colors, and a longer season gives tropical invasive insects and fungi more opportunities to damage native species. Drought between large storms allows for more forest wildfires too.
Well, it is sad to think that in fall we may never again see the brilliant eruption of color we have come to expect. They are sending us warning signals. Whatever their color, we need trees to absorb carbon dioxide emanating from fossil fuel burning and gas-burning vehicles. We need even more trees given forest destruction from western wildfires.
Last week an event at Ocoee Whitewater Center celebrated a Howell family donation of 661 forested acres to Cherokee National Forest. The land contains headwaters of a tributary to the Conasauga River.
Several organizations were involved to make it happen: The Federal Land & Water Conservation Fund, The Nature Conservancy, the Conservation Fund, National Wild Turkey Federation, Lyndhurst Foundation and the U.S. Forest Service.
Assuming Cherokee National Forest will keep those trees healthy and growing, this is one way to keep trees working to slow the rate of climate change. Now you may not have a forest give, but you can donate to organizations planting or protecting trees. You can also join Tennessee Environmental Council’s 250K Tree Day project or just plant your own and hope for a colorful fall.
Sandra Kurtz is an environmental community activist, chair of the South Chickamauga Creek Greenway Alliance, and is presently working through the Urban Century Institute. You can visit her website to learn more at enviroedu.net