Climate Change Causing Carbon Dioxide Also Making Trees Delay Autumnal Colours

Do those fall colors seem to show up later and later? Scientists say we can blame increasing amounts of carbon dioxide in the atmosphere for prolonging the growing season of trees.

“Carbon dioxide fools the trees,” says Wendy Jones, a research associate at Michigan Technological University who conducts research at the Aspen FACE site in northern Wisconsin. “They think they should still be growing when they ought to be going through autumnal senescence”—changing their colors and settling down for a long winter’s nap.

The phenomenon was initially documented at the Aspen FACE (Free Air Carbon dioxide Experiment) site in Rhinelander. Plots of trees are exposed to varying levels of carbon dioxide and ozone to gauge how increasing concentrations of greenhouse gases will affect northern forests.

Delaying the color change may actually be good news for forest products industries, since it suggests that trees will become a bit more productive due to the extra carbon being taken up in the autumn, along with the increased photosynthesis throughout the growing season.

Jones cautions that other variables also affect tree growth and senescence, however. In other words, even with higher levels of carbon dioxide, the annual autumn spectacle could still come early. “It’s been a dry year here,” she said, which generally means that trees lose their leaves earlier.