Environmental (Commonwealth Union)_ In a remarkable revelation, scientists have determined that New England’s salt marshes act as powerful carbon sinks, capturing an amount of carbon equivalent to the annual emissions of nearly 10 million cars within their upper meter of soil. Even more impressively, these marshes continue to accumulate carbon every year, sequestering additional emissions comparable to those of approximately 15,000 more vehicles.
A team of researchers from the University of Massachusetts Amherst has developed an innovative, highly precise method to quantify carbon storage in the region’s salt marshes. Their groundbreaking study offers critical insights into the ecological significance of these coastal ecosystems and their role in mitigating climate change.
“Tidal marshes possess an extraordinary ability to continuously increase their carbon storage capacity,” explains Wenxiu Teng, the study’s lead author and a Ph.D. candidate in the Department of Earth, Geographic, and Climate Sciences at UMass Amherst. “Unlike many other carbon storage systems, they don’t reach a saturation point.”
Coastal environments play an essential role in regulating atmospheric carbon dioxide. The ocean itself absorbs nearly one-third of industrial carbon emissions, and salt marshes further contribute to this process by acting as natural carbon repositories. With each passing tide, waves, and storms, layers of sediment rich in organic material are deposited within the dense grasses of the marsh, effectively locking carbon away. As sea levels rise due to glacial melt, these marshes grow vertically, continuously expanding their storage capacity.
Published in the Journal of Geophysical Research: Biogeosciences, the study employs satellite technology to analyze marshland water depth and vegetation density. Researchers utilized the Normalized Difference Water Index (NDWI) to assess seasonal changes in plant growth and water retention across marshes stretching from Long Island Sound to the Gulf of Maine. By collecting 410 soil samples from 19 different sites and correlating them with satellite observations, the team identified precise conditions under which remote sensing data closely mirrored field measurements. This technique allows for a scalable approach to mapping carbon sequestration in salt marshes worldwide.
“Salt marshes are significantly more stable carbon sinks than forests or other terrestrial ecosystems,” says Brian Yellen, Massachusetts’ state geologist and research assistant professor at UMass Amherst. “While technological innovations for carbon capture continue to evolve, we already have a naturally efficient system in place. Our study quantifies the scale of this natural process and provides a replicable method for assessing similar ecosystems globally.”
However, the researchers also issue a stark warning: the vast amounts of carbon stored in salt marshes could become a substantial climate threat if these ecosystems are degraded. Development, pollution, and rising environmental stressors could disturb the delicate balance of these habitats, leading to the release of massive quantities of greenhouse gases back into the atmosphere.
“If salt marshes are lost due to human activities or climate-related stressors, they would transition from being carbon sinks to significant carbon emitters,” Yellen cautions. “The very asset that helps mitigate climate change could end up exacerbating it.”
The study highlights the urgency of protecting salt marshes as part of broader climate action strategies. With ongoing research and conservation efforts, these wetlands can continue serving as a crucial defense against global warming, offering a nature-based solution to carbon capture that is already working effectively.
As scientists refine their understanding of salt marshes’ carbon storage potential, the findings reinforce the necessity of safeguarding these environments. The humble salt marsh, if preserved, can play a crucial role in shaping a more resilient future in a world seeking sustainable climate solutions.
