Why climate change is making it harder to chase fall foliage

Satellite observations indicate a delayed fall and the reason being warmer temperatures

Droughts that cause leaves to turn brown and wither before they can reach peak colour. Heat waves prompting leaves to fall before autumn even arrives. Extreme weather events like hurricanes that strip trees of their leaves altogether.

For a cheery autumnal activity, leaf peeping is facing some serious threats from the era of climate change. Leaf peeping, the practice of travelling to watch nature display its fall colours, is a beloved annual activity in many corners of the country, especially New England and New York. But recent seasons have been disrupted by weather conditions there and elsewhere, and the trend is likely to continue as the planet warms, said arborists, conservationists and ecologists.

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Typically, by the end of September, leaves cascade into warmer hues throughout the US. This year, many areas have yet to even pivot from their summer green shades. In northern Maine, where peak conditions typically arrive in late September, forest rangers had reported less than 70 per cent colour change and moderate leaf drop on Wednesday.

Across the country in Denver, high temperatures have left ‘dead, dry edges of leaves’ early in the season, said Michael Sundberg, a certified arborist in the area.
“Instead of trees doing this gradual change, they get thrown these wacky weather events. They change all of a sudden, or they drop leaves early,” Sundberg said. “Its been a few years since we’ve had a really good leaf year where you just drive around town and see really good colour.” The reason climate change can be bad for fall foliage has a bit to do with plant biology. When fall arrives, and day length and temperature drop, the chlorophyll in a leaf breaks down, and that causes it to lose its green colour. The green gives way to the yellows, reds and oranges that make for dramatic autumn displays.

Achieving those peak colours is a delicate balance, and one jeopardised by changes in the environment, said Paul Schaberg, a research plant physiologist with the US Forest Service based in Burlington, Vermont. Warm fall temperatures can cause leaves to remain green longer and delay the onset of what leaf peepers look for in terms of fall colour, he said.