ENVIRONMENT: Climate Change Threatens Fall Colors

fall leaf


COLLEGE PARK — Fall colors are arriving later and are fading more quickly because of climate change, according to researchers.
The climate-driven changes are already visible in some forests in New England. Scientists worry that leaf-peeping hotspots in Maryland also could eventually see duller foliage and delays in the start of leaf season.

“It [climate change] certainly could have an impact here, as well,” said Saran Twombly, a researcher at the National Science Foundation, who studies the impact of climate change on foliage.

In Massachusetts’ Harvard Forest, data collected by retired Harvard professor John O’Keefe suggests that leaves are changing color four days later than they did in 1993.

In New Hampshire, sugar maples are shedding their leaves two to five days later than two decades ago, according to data collected by the Hubbard Brook Experimental Forest in Woodstock, N.H.

Warmer temperatures and erratic weather patterns driven by climate change have an adverse affect on tree health, according to phenologists – those who study the effects of seasonal changes on plants.

As the weather turns cooler in the fall, plants stop producing chlorophyll – the pigment that colors leaves green. This allows other colors to shine through – red, yellow or orange, depending on the species. Warmer-than-usual fall temperatures delay this color change.

As temperatures rise, certain types of hardwood trees that produce colorful foliage, like sugar maples, may be forced to move further north. Maples heavily populate forests in the Northeast, and produce bright red foliage in the fall.

The trees may migrate because it isn’t cold enough for them to produce seeds that germinate, according to Joseph Sullivan, an ecology professor at the University of Maryland.

The New Hampshire Department of Environmental Services predicts that if temperatures continue to rise, these hardwoods could migrate up to 300 miles north.

“The climate’s warmer so these organisms can live where they couldn’t before,” Sullivan said. He likened certain tree diseases to human ones, such as malaria, which thrive in warmer climates. Without the vibrant colors of these hardwoods, he said, the fall forest could look duller.
Erratic weather patterns, like those that produced nationwide droughts this summer, are also detrimental to trees. Trees begin to shed their leaves prematurely during droughts, looking sparse and dull.

Most of the studies done so far focus on forests in New England. Scientists said that more research is needed to determine whether these changes are occurring in leaf-peeping hotspots further south, like Western Maryland.

Few regional studies exist on fall foliage patterns because it’s difficult to collect such data, said Jake Weltzin, director of the National Phenology Network. The network has been trying to establish a system that uses satellite imagery to study foliage more extensively.
“Bottom line, we need more information for many places in the U.S., including the (Washington) D.C. area,” he said in an email. Researchers in New England worry that if these trends persist, they could discourage leaf peeping tourists, damaging small towns that depend on them.

“There’s a great concern that this would impact the tourism industry in places like Vermont and Massachusetts, where people go specially for the fall foliage,” Twombly said. In parts of Maryland, leaf peeping is also vital to fall tourism.
Attendance triples during peak foliage season in Garrett County, a popular destination for leaf peepers. Last fall, it welcomed 240,000 visitors. More than 90 percent said that leaf peeping was the biggest reason for their visit, according to data gathered by the Garrett County Chamber of Commerce.

Tourism officials in Maryland said Maryland forests don’t appear to be any less brilliant than in the past. They also said they have not noticed any delays in the the onset of leaf season.

“We haven’t noticed any negative impact on (tourism) growth,” said Sarah Duck, director of tourism for Garrett County. “This summer has been one of  the best we’ve ever had and it seems like fall is shaping up to be the same.”

Foliage enthusiasts plan their trips around peak season, which lasts from mid-September to mid-October in Western Maryland, said Chuck Hecker, a spokesperson for the Maryland Park Service. If delays reduce the duration of the peak season, he said, it could adversely affect tourism in the area.
Experts at the Maryland Department of Natural Resources don’t see a direct link between climate change and foliage in Maryland, according to Karis King, a spokesperson for the agency.

However, phenologists said that the link exists, and it’s only a matter of time before the effects of climate change on foliage are visible in Maryland.