Tri-state area trees reach their peak color this weekend, while some scientists speculate climate change could delay fall foliage now or in the near future.
"This weekend through next weekend is looking like peak colors for us," said Steve Swinconos, an Iowa Department of Natural Resources forester in Anamosa. Swinconos' district includes Dubuque and Jackson counties.
Credit recent dry weather for the memorable leaf displays.
"The weather is amplifying our fall colors, making them last a lot longer," Swinconos said. "We had the perfect weather pattern for good fall color this year."
Studies in Europe and in Japan already indicate leaves are changing color and dropping later, so it stands to reason that it's happening here as well, said Richard Primack, professor of biology at Boston University.
"The fall foliage is going to get pushed back," Primack warned.
Down the road, scientists say, there could be implications not just for ecology, but for the economy, if duller or delayed colors discourage leaf-peeping tourists. The budding of plants each spring is tied almost exclusively to warming temperatures, while fall's colors are linked to cooling temperatures, decreasing sunlight and soil moisture.
"Fall is still an enigma," said Jake Weltzin, executive director of the National Phenology Network in Arizona and an ecologist with the U.S. Geological Survey.
Scientists caution that heavy rain, drought-like conditions or temperature extremes can cause dramatic year-to-year fluctuations that don't establish a long-term trend. For example, heavy rainfall in New England this spring, followed by a deluge caused by Irene, is resulting in fungal growth that's causing some trees' leaves to turn brown and drop earlier than normal.
William Ostrofsky, forest pathologist with the Maine Forest Service, is skeptical about whether there's a proven link between fall foliage and climate change.
"I just don't know that there's any evidence to indicate there's a trend one way or the other," said Ostrofsky, who points out that year-to-year fluctuations make it difficult to discern long-term trends.
While there's no definitive study in the U.S., some data point toward later leaf drop:
* Researchers at the NASA Goddard Space Flight Center and at Seoul National University in South Korea used satellites to show the end of the growing season was delayed by 6 1/2 days from 1982 to 2008 in the Northern Hemisphere.
* In Massachusetts, the leaves are changing about three days later than they were two decades ago at the Harvard Forest 65 miles west of Boston, according to data collected by John O'Keefe, a retired Harvard professor and museum coordinator.
* In New Hampshire, data collected at the federal Hubbard Brook Experimental Forest in Woodstock suggest sugar maples are going dormant two to five days later than they were two decades ago.
Scientists are getting serious, and in Maine they're enlisting gardeners, 4-H programs, teachers, students and families in their efforts to collect data.
"There are signs everywhere that things are changing -- 'how' is the question. Some species are being affected while others are not," said Esperanza Stancioff, of the University of Maine Cooperative Extension and Maine Sea Grant, who has trained 195 citizen scientists to enter data online in her "Signs of the Season" phenology project.
However, this year, the tri-state area's peak fall foliage arrived right on time.
"It's fairly predictable," Swinconos said. "It does change a little, depending on the weather conditions."
The Associated Press contributed