In a groundbreaking study published in the prestigious Proceedings of the National Academy of Sciences, a team of scientists has unveiled a pioneering method to detect early signs of salt marsh degradation long before visible decline is apparent. This novel approach hinges on monitoring belowground biomass—the roots and rhizomes of marsh vegetation—that serve as critical indicators of marsh health and resilience in the face of escalating sea-level rise. By leveraging remote sensing data and sophisticated modeling, researchers have opened a promising frontier in coastal ecosystem management, allowing timely intervention to prevent irreversible marsh loss.
Salt marshes, often overlooked until their degradation becomes unmistakable, are invaluable ecosystems lining many coastlines. Their intricate belowground root networks not only stabilize soil and build elevation but also form Blue Carbon reservoirs that sequester atmospheric carbon dioxide, mitigating climate change. These wetlands provide a first line of defense against storm surges and flooding, filter pollutants to improve water quality, and sustain diverse aquatic and terrestrial wildlife, forming the backbone of coastal biodiversity and local economies reliant on fishing and recreation.
The interdisciplinary team, spearheaded by Kyle Runion of the University of Georgia and Colorado State University, employed the Belowground Ecosystem Resiliency Model (BERM) to analyze satellite imagery and field data spanning over a decade along Georgia’s coastline. BERM captures the complex relationship between aboveground plant vigor and belowground root biomass, revealing a previously hidden disjunction wherein marsh grass may appear lush above the surface while simultaneously suffering root decline beneath. This dichotomy undermines the traditional reliance on visual assessments alone to gauge marsh health.
Sea-level rise, an accelerating consequence of global warming, intensifies inundation cycles that exert profound physiological stress on marsh vegetation. While moderate flooding can stimulate marsh growth by flushing salts and providing nutrient-rich sediments, excessive and prolonged submergence deprives roots of oxygen, triggering a decline in belowground biomass. The study found that since 2014, 72% of Georgia’s coastal marshes exhibited significant root biomass reduction, with nearly one-third facing severe deterioration, foreshadowing widespread marsh drowning if unaddressed.
The implications of declining belowground biomass are far-reaching. As root systems weaken, marsh elevation fails to keep pace with rising sea levels, leading to vegetation drowning and loss of critical habitat. This degradation jeopardizes carbon sequestration capabilities, amplifies coastal erosion, and diminishes the protective buffer against storm surges. Detecting these early physiological stress signals, therefore, is essential not only for conservation but also for sustaining the myriad ecosystem services these marshes underpin.
The novel remote sensing application within BERM integrates environmental variables such as elevation, tidal inundation patterns, and climatic factors with spectral signatures of plant traits observable from space. This multifactorial approach refines predictions of both above- and belowground biomass, transcending prior limitations that relied heavily on site-specific field observations. By doing so, it enables scalable, real-time monitoring of vulnerable marshes across diverse coastal regions, empowering stakeholders to prioritize restoration efforts effectively.
Co-author Jessica O’Connell from Colorado State University emphasizes the urgency of early intervention. “By the time marshes show visible distress aboveground, much of the foundational root system is already compromised,” she notes. “This early warning system means we can direct resources smartly, protect these irreplaceable ecosystems, and avoid the costly consequences of marsh loss that ripple through communities and economies.” The study reinforces conservation as a cost-effective alternative to engineered infrastructure solutions, providing a natural safeguard that self-maintains and adapts to changing conditions.
The study specifically focused on Spartina alterniflora, a dominant salt marsh grass species along the U.S. Atlantic and Gulf coasts, whose robust root networks traditionally enable marshes to maintain surface elevation relative to sea level. The researchers meticulously validated their model predictions with extensive field measurements from the Georgia Coastal Ecosystems Long Term Ecological Research Program. These data elucidated that aboveground biomass alone could not reliably indicate marsh health, as root decline often precedes visible vegetation loss by years.
Importantly, this research extends beyond regional application. The investigators are now advancing BERM towards universal applicability by calibrating it for different marsh vegetation types and environmental conditions worldwide. This scalability is critical given the global threat of sea-level rise and the vital role of coastal wetlands in global carbon cycles and climate resilience. Tailoring the model to diverse ecosystems promises to revolutionize how coastal managers and policymakers understand and respond to marsh vulnerability on a planetary scale.
The team underscores that marsh conservation is not merely an environmental imperative but an economic and social one as well. Coastal communities often harbor deep cultural and economic ties to wetlands, relying on the ecosystem services they provide. With sea-level rise poised to intensify, the ability to predict marsh failure well in advance offers a crucial window for community engagement, adaptive management, and landscape-scale restoration strategies that sustain both nature and people.
This research represents a fusion of ecological insight, technological innovation, and long-term fieldwork, coalescing into a predictive framework that charts a path toward sustaining the resilience of coastal marshes amid environmental change. Funded by the National Science Foundation, NASA, and NOAA, the study exemplifies how collaborative, interdisciplinary science can address some of the most pressing environmental challenges of our time.
As sea-level rise accelerates globally, the message within this study is clear: protecting belowground biomass—the often-invisible root systems—is paramount to preserving salt marsh integrity. With emerging technologies like BERM and satellite remote sensing, scientists and conservationists now possess a powerful early warning system to detect vulnerability and activate preservation efforts well before catastrophic marsh loss occurs. The future health of coastal zones, their biodiversity, and their human communities may well depend on such innovations.
Subject of Research: Salt marsh degradation and early detection of vulnerability through declining belowground biomass
Article Title: Early warning signs of salt marsh drowning indicated by widespread vulnerability from declining belowground plant biomass
News Publication Date: 23-Jun-2025
Web References:
- https://www.pnas.org/cgi/doi/10.1073/pnas.2425501122
- DOI: 10.1073/pnas.2425501122
Image Credits: Kyle Runion/Colorado State University
Keywords: Salt marshes, Wetlands, Coastal ecosystems, Remote sensing, Sea level rise, Ecological degradation, Root growth, Conservation ecology, Marine conservation, Ecosystem management, Blue carbon, Carbon sequestration, Environmental monitoring, Spartina alterniflora
