Warmer Temperatures, Drought Delaying or Eliminating Fall Foliage in Some Parts of U.S.

Warmer temperatures, droughts and extreme weather events have eliminated fall foliage in parts of the country, as some areas approach their peak season, according to the Associated Press.

Peak fall colors are dependent on the weather and can be jeopardized by changes in the environment, Paul Schaberg, a research plant physiologist with the U.S. Forest Service based in Burlington, Vermont, said.

Warm temperatures can keep leaves green longer, and dry summers can put stress on trees and cause their leaves to avoid fall colors altogether, according to a 2003 study in Tree Physiology that Schaberg co-wrote.

"If climate change is going to mean significant drought, that means trees are going to shut down, and many trees are just going to drop their leaves," Schaberg told the AP. "Severe droughts that really mean that the tree just can't function—that doesn't improve color."

For more reporting from the Associated Press, see below.

Typically, by the end of September, leaves cascade into warmer hues throughout the U.S. 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 percent color 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 [by] these wacky weather events. They change all of a sudden, or they drop leaves early," Sundberg said. "It's been a few years since we've had a really good leaf year where you just drive around town and see really good color."

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 color. The green gives way to the yellows, reds and oranges that make for dramatic autumn displays.

This summer's heat wave in the Pacific Northwest brought temperatures of over 110 degrees Fahrenheit to Oregon, and that led to a condition called "foliage scorch," in which leaves prematurely browned, said Chris Still, a professor at the Forest Ecosystems and Society department at Oregon State University.

The leaves' pigment was degraded and they fell shortly thereafter, Still said. That will lead to a less scenic fall season in parts of Oregon.

"That's a really big example of color change just due to heat wave shock," Still said.

Climate change also poses longer-term threats that could disrupt leaf peeping, the practice of traveling to view fall colors in nature annually, particularly in New York and New England. The spread of diseases and invasive pests and the northward creep of tree species are all factors tied to warming temperatures that could make for less vibrant fall colors, said Andrew Richardson, a professor of ecosystem science at Northern Arizona University.

The onset of fall colors, which has been drifting later into the fall, could also continue to arrive later, said Jim Salge, foliage expert for Yankee magazine.

"My observations in the last decade have had more years that were later than what we would consider historical averages," he said.

The economic impact of poor leaf-peeping seasons could also be consequential. Officials throughout New England have said fall tourism brings billions of dollars into those states every year.

Conservationists say that's a good reason to focus on preserving forests and reducing burning fossil fuels. Recent fall seasons have been less spectacular than typical in Massachusetts, but leaf peeping can stay a part of the state's heritage if forests are given the protections they need, said Andy Finton, landscape conservation director and forest ecologist for the Nature Conservancy.

"If we can keep the big, important forests intact, they will provide what we've depended on—clean air, clean water, clean forests, as well as fall inspiration," Finton said.