If you’re lucky enough to live in a place where the trees put on a dramatic, multicolor show when fall rolls around, maybe you’ve noticed some distinct, sweet smells hitching a ride on the brisk air.
Where exactly do those scents come from? Simply put, it has a lot to do with dying and decomposing vegetation, said Theresa Crimmins, director of the USA National Phenology Network.
“That’s what fall is all about. Leaves are falling off the trees and the bacteria and fungi that are in the soil are actively digesting those things,” Crimmins said. “And in the process, various gases and volatile organic compounds are being released, and that’s a lot of what the smells are that we’re experiencing.”
Scents can also be clearer and more prominent due to the shift in atmospheric conditions, Crimmins said. The heat and humidity of summer air traps all kinds of smells, she said, creating a “mishmash” for our noses. But as the days get cooler and crisper, there are fewer volatile organic compounds in the air, and we’re better able to distinguish the ones that are released by dying and decomposing vegetation, leaving that sweet smell front and center.
Fall has begun to show up later in the year compared with previous decades, primarily because of warmer average temperatures driven by climate change. And when trees endure drought, they sometimes ditch their leaves earlier in the year because “the cost of the leaves exceeds the benefit,” said Benjamin Wong Blonder, an ecologist at the University of California Berkeley College of Natural Resources. That could mean we’ll see more years that skip the incredible full-color display, as is happening in parts of the Northeast now.
This video was produced by Megan McGrew and Bella Isaacs-Thomas. It was edited by Molly Finnegan, Julia Griffin and Yasmeen Alamiri.
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