by Tiegan Paulson
photos by Tiegan Paulson
Take a walk around Eagle Lake, The Bubbles, or many other paths in Acadia National Park, and you’ll notice the beech trees are covered in lumps and holes, the leaves shriveled and discolored. Beech bark disease and beech leaf disease are present in Acadia, and the impacts are easy to see. Several other tree species in the park have been similarly affected by invasive organisms, and it seems to be merely good luck that the same has not happened to red spruce, the most common tree in Acadia.
Red spruce make up about half the park’s forests, and they remain relatively unaffected by invasive species that can kill trees. Given the importance of red spruce to Acadia, managers are worried about pests or pathogens that might target red spruce but have yet to be discovered or introduced. Such scenarios are called ‘black swan events,’ or events that are unforeseen but have large consequences.
Matthew Duveneck, of New England Conservatory, with help from Nicholas Fisichelli (Schoodic Institute) and Kathryn Miller (National Park Service), put Acadia’s forests to the test using a pair of forest landscape models. The modeling simulated tree species growth, dispersal, and death over time given projected conditions, such as temperature, carbon dioxide, light, and water. The models also considered landscape scale, like insect spread and forest management. They simulated hypothetical disturbances that specifically targeted red spruce; mainly, one that spreads slowly and one that spreads quickly.
“The largest effects to future forests may be some insect that we don’t even know about,” Duveneck said. “Maybe it will be a little bit drier, or wetter, or warmer than it was before, and some future pathogen that is sensitive to a changing climate takes off. All of a sudden, ten years from now it’s gonna be like, bam, all the red spruce are gone. While we can’t predict the future, we can explore scenarios of unprecedented but plausible futures.”
The study, published in May in the journal Ecosphere, found that these “black swan” disturbances could have large impacts on red spruce. Modeling that included management strategy was a unique piece of the study: human actions are not often modeled in climate change impact studies, but here the team accounted for three possible management actions in response to disturbance. Based on the RAD (resist – accept – direct) framework, co-developed by Fisichelli, the actions included resisting by planting more spruce trees, accepting by allowing the forests to naturally adapt, or directing by planting new tree species that might be better adapted to the emerging climate.
“We know the future won’t look quite like the past and managers are grappling with finding the appropriate response,” said Fisichelli. “The RAD framework provides a spectrum of adaptation approaches to assess management interventions.”
In the absence of major disturbances, the team’s models indicate red spruce will still be doing well in 2110, despite previous studies finding climate change to significantly reduce its suitable habitat in Acadia. The species may be able to endure changing conditions, effectively keeping Acadia well forested.
“These results give us some optimism for red spruce’s future in the absence of an unexpected event, like an introduced pest, and provide insight into how to respond if it occurs,” said Miller.
It is entirely possible major disturbances like the ones modeled in this study will not occur. That said, managers now have a better sense of how their actions might impact the situation if a ‘black swan’ does arrive—and what to expect the forests to look like.
Original publication: Matthew Duveneck et al. Novel threats and response to Acadia National Park forests: Simulating the resist–accept–direct management framework. Ecosphere (2026). Doi: https://doi.org/10.1002/ecs2.70666