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At the same time, Marra is aware that tomography is not a practical substitute for the Forest Service’s carbon estimate system — which itself is a clunky and labor-intensive slog. But it could provide a valuable way to augment those estimates.
“Those are very, very impressive results,’’ says Kevin Griffin, a tree physiologist at Columbia University and its Lamont-Doherty Earth Observatory. “They obviously have obtained a lot of precision in the techniques.”
“The results are important,” he adds, “but whether internal tree decay is the single most burning question? Probably not. There’s probably bigger fish to fry before we get there.”
Among them, he says are forest growth rates and overall tree health and age, as well as the impact of harvesting and other kinds of losses, including disease.
A tree’s architecture and height could also play large roles in carbon sequestration, says Reinmann of the City University of New York’s Advanced Science Research Center, as could the makeup of the forest landscape. His own research, for instance, found trees grow faster and have more biomass at the edge of fragmented forest.
“I think they’re making a good point that we’re probably over-estimating” carbon storage levels, says Aaron Weiskittel, director of the University of Maine’s Center for Research on Sustainable Forests.
Even so, Weiskittel and others — including Marra — say the research needs to be scaled up to many more tree types and full forests. For his part, Marra would like to sample forests randomly with many more trees and controlling for factors including species, age, and soil characteristics.
The goal, he says, is to develop a methodology for generating data to provide better carbon estimates for more than three tree types in one small part of the country.
“We need to use tomography to refine models so we’re more accurately assessing the role that forests are playing as sequesterers or climate change mitigators,” Marra says. “We don’t want to be over-estimating the roles that they play.”
Jan Ellen Spiegel is a freelance writer and editor based in Connecticut. Her work appears regularly in numerous local and national publications, including The Connecticut Mirror, InsideClimate News, Yale Climate Connections, and The New York Times.
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