For Immediate Release
A new study finds that climate change may have a range of contrasting effects on coastal forests, both slowing and enabling growth in areas where sea levels are rising and storms are more common.
Researchers compared a decade of forest growth data from two types of environments across the mid-Atlantic, southeastern, and Gulf coasts of the United States: coastal areas less than five meters (20 feet) above sea level and inland areas between 30 and 50 meters (more than 100 feet) in elevation. They found that while forests have expanded in both environments in the last 10 years, some coastal areas have seen significantly lower tree growth and higher mortality than areas of higher elevation.
Marcelo Ardón, associate professor in the North Carolina State University College of Natural Resources, is the lead author of a paper on the study. He said that the expansion of forests in both middle and lower elevations was unexpected.
“We were a little surprised that we found increased forest area and forest biomass in both elevations, and that could be to do with the abandonment of agricultural land,” Ardón said. “Despite that expansion, we found that low-lying areas exposed to rising seas still had less overall biomass growth than those at higher elevation.”
Researchers were also surprised to find a positive correlation between forest growth and increased coastal storms. Despite also resulting in large numbers of dead trees, the newly cleared space left behind may allow new growth to flourish, Ardón said.
“In a way, these storms may serve a similar function to a controlled burn,” he said, referencing the forestry practice of using targeted fires to thin out dense, overgrown areas of vegetation. “By knocking down these older trees, they clear out the canopy overhead and allow more light to reach the forest floor. It resets the succession for younger trees.”
Researchers used data from the United States Department of Agriculture’s Forest Inventory and Analysis program, which is unique in that it relies on hand-collected field data rather than satellite monitoring. This allowed the researchers to analyze the carbon storage capacity of the trees knocked down by coastal storms, which the study highlights as an important area for future research.
“In the process of studying these other effects of climate change, we also learned that we really need to spend more time understanding this dead wood,” Ardón said. “There is a lot of carbon in those dead trees, both standing and on the ground, and we don’t understand it very well.”
The study “Coastal carbon sentinels: A decade of forest change along the eastern shore of the US signals complex climate change dynamics,” is published in PLOS Climate. Co-authors include Kevin M. Potter and Christopher W. Woodall, USDA Forest Service, and Elliot White Jr, Stanford University. Funding for the study was provided by the National Science Foundation grant DEB-1713502.
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Note to Editors: The study abstract follows.
“Coastal carbon sentinels: A decade of forest change along the eastern shore of the US signals complex climate change dynamics”
Authors: Marcelo Ardon, NC State University; Kevin M. Potter and Christopher W. Woodall, USDA Forest Service; and Elliot White Jr, Stanford University
Published: Jan. 9, 2025
DOI: 10.1371/journal.pclm.0000444
Abstract: Increased frequency and intensity of storms, sea level rise, and warming temperatures are affecting forests along the eastern coast of the United States. However, we lack a clear understanding of how the structure of coastal forests is being altered by climate change drivers. Here, we used data from the Forest Inventory and Analyses program of the US Forest Service to examine structure and biomass change in forests along the mid-Atlantic, Southeastern, and Gulf coasts of the US. We selected plots that have been resampled at low (5 m) and mid (30–50 m) elevations in coastal areas of states from Texas to New Jersey, allowing us to determine change in live trees, standing dead wood, and downed dead wood biomass (and carbon) stocks across a decade at the county level. Forest area increased by 1.9% and 0.3% in low and mid elevation counties, respectively. Live tree biomass density increased by 13% and 16% in low mid elevation counties, respectively. Standing dead biomass decreased by 9.2% and 2.8% in low and mid elevation counties, respectively. Downed dead wood increased by 22% in low elevation counties and decreased 50% in mid elevation counties. Annualized growth and harvest were both higher (16% and 58% respectively) in mid elevation than low elevation counties, while annualized mortality was 25% higher in low elevation counties. Annualized growth in low elevation counties was negatively correlated to sea level rise rates, and positively correlated to number of storms, illustrating tradeoffs associated with different climate change drivers. Overall, our results illustrate the vulnerability of US coastal low and mid elevation forests to climate change and sea level rise, with indications that the complexity and rate of change in associated ecosystem functions (growth, mortality, and carbon storage) within the greater social environment (agricultural abandonment) may increase.
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