It’s something people in southern Ontario take for granted – as summer fades, cooler air rolls in and the leaves burst into those fiery, warm hues we love to snap pictures of.
Except that’s not happening this year. Fall is looking … a little dull.
“This year’s October was about four degrees warmer than it was last year,” Sean Thomas told Global News one afternoon at Riverdale Park. The research professor specializing in forestry and environmental change says you can blame this year’s lackluster autumn show, particularly in Toronto, partly on climate change.
“Climate change predictions are for warmer temperatures of course, but also for increased cloud cover,” said Thomas. “That combination — if trees don’t receive the cool temperatures and the high light in the fall at the right time, then they won’t be triggered to form the red pigments.”
According to Thomas, those red pigments are what make those fall colours pop — acting as antioxidants and sunscreen created by the tree to protect its leaves as it extracts nutrients to redeploy for next season. But an unusually warm fall meant the trees did not receive that cold temperature signal to create those red pigments (also known as anthocyanin).
He said there are other factors at play leading to this years’ foliage flop. Toronto having a pretty pronounced urban heat island and sizzling heat waves this past summer have led to foliage scorching — where the extreme heat turns leaves prematurely brown.
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Leaf scorching on a Hackberry Tree in Riverdale Park.
Doug Gamey/Global News Screenshot
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Powdery mildew covering this leaf of a tree in Riverdale Park.
Doug Gamey/Global News Screenshot
Some trees have also been ravaged by mildew and insect infestations this past summer.
“If the trees have lost their leaves, then there’s not the leaves there to turn,” said Thomas.
In addition, he points out some of the brown being seen this year is due to Toronto being home to plenty of non-native trees, like the Norway maple, which don’t actually produce fall colours.
“So when you’re looking out on the ravines and Toronto, a lot of what you’re seeing is not the native species. It’s invasive Norway maple and they don’t turn.”
Thomas says on an average year, by end of September/early October the leaves will start to change, reaching peak colour by the end of that month before dropping.
But this year, many trees have hung onto their summer green well into November, with some missing their fall colour change altogether.
Warmer temperatures are also delaying when trees drop their leaves. A tree canopy in Pickering was mostly bare-branch in early November of last year, but this year, still showed some lush green in late November.
The more muted fall colours are leaving some leaf-peepers less than thrilled, especially when considering climate change could make it the new norm.
“I mean it sucks,” said one young couple from Ajax. “Because you go from like being a kid and seeing it so bright and now seeing the change…” the woman’s voice trails off sadly as she gestures to the trees at Riverdale Park.
“It’s very sad,” said a man sitting on a bench in the park. “It’s a very sad consequence of total irresponsibility … everything must be done in order to help nature because it’s all we have.”
© 2021 Global News, a division of Corus Entertainment Inc.
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