Although forest health inventories show that Pennsylvania’s forests are generally healthy, Sharpe reminds us that survey data only answer some kinds of questions. “When doing a scientific survey, scientists randomly pick plots all over the state,” he says. “Half of those plots could fall on areas, for instance, where there’s no maple decline and only 5 percent where trees are dead and dying. Imagine you’re being checked by a dermatologist for a melanoma. You have 100 moles on your body and one of them is cancerous. The doctor can’t look at all 100 moles, so he or she designs a random survey and looks at 10 percent. Or, he or she looks at all of the moles and checks out the irregular ones. Which approach would you be more comfortable with?

Following salvage logging, some sugar maples are left to provide a seed source for the new forest, but most are dead within a few years.

“Random surveys are liable to miss the problem completely, particularly when you’re looking at millions of acres of forestland. You’re better off going to where the trees are dying to try to figure out why. Then, you can figure out the potential for the problem to spread and assess the risk to healthy trees.”

Sharpe fears that as soils continue to acidify, the decline may spread to other species. “We’re still a long way from knowing the best way to manage air pollution in our forests,” he says. “In ecological work, everything taught in the classroom and written about in every textbook is based on circumstantial evidence. You can’t go into a place as complex as a forest and prove anything in a cause-and-effect way. You just amass circumstantial evidence and go with your best call.”

Although forest health researchers don’t agree on whether sugar maple decline is a “canary in the coal mine” or part of a larger cycle of climate variability, insect cycles, and slow change, they all agree that Pennsylvania’s forests face new challenges. Complex interactions among plant species and genotypes, site nutrient characteristics, soil moisture, deer, insects, and various pollutants will continue, as will efforts to understand and manage them.

“With all of the tremendous research we’re doing at Penn State and the support of federal and state agencies, and private industries, we’re bound to come up with the information needed to help us understand and solve these problems,” says Skelly.

Thanks to Susan Stout, project leader with the USDA Forest Service’s Forestry Sciences Laboratory, Irvine, Pennsylvania, for
providing feedback on this story.

Faculty and staff referenced in this article are Dave DeWalle, professor of forest hydrology; Jon Ferdinand, research assistant in the Environmental Resources Research Institute; Jim Lynch, professor of forest hydrology; Bill Sharpe, professor of forest hydrology; John Skelly, professor of plant pathology; and Kim Steiner, professor of forest biology. Steve Horsley is a plant physiologist with the USDA Forest Service’s Forestry Sciences Laboratory, Irvine, Pennsylvania, and an adjunct faculty member in the School of Forest Resources. Jae Choen Lee was a visiting scientist from the Korean Institute of Forest Genetics, Seoul, Korea.

Research has been funded by Allegheny Power of Greensburg, Pa.; EXXON/MOBIL Corporate Giving Program;
North American Maple Syrup Council; Pa. Department of Conservation and Natural Resources, Bureau of Forestry; Penn State’s College of Agricultural Sciences; Pa. Department of Environmental Protection; Penn State’s School of Forest
Resources; USDA-Forest Service; and U.S. EPA, STAR Program.