Climate change is driving species and habitats poleward across the U.S., reshaping ecosystems in ways that challenge traditional conservation planning. Along the southeastern Atlantic coast, one of the most visible transitions is the expansion of tropical mangroves into temperate salt marshes, as warming winters and fewer extreme freeze events reduce climatic barriers that once limited mangrove growth.
Mangroves and salt marshes are both highly valuable coastal wetlands, but they provide different ecological functions. Mangroves provide stabilization and carbon storage, while salt marshes support species adapted to open, herbaceous wetlands, while also filtering water and cycling nutrients. As mangroves expand into marsh-dominated areas, the structure, biodiversity, and services of these coastal systems may change in profound ways. Understanding where this transition is likely to occur is critical for long-term coastal resilience planning.
Enes Gramoso, L.I., Carroll, D., Cavanaugh, K.C., Bardou, R., Osland, M.J. and Van der Stocken, T. 2026. 21st‐century mangrove expansion along the Southeastern United States. Global Change Biology 32(1): e70676. DOI: 10.1111/gcb.70676.
New research projects how mangroves may expand along the Atlantic coast from Florida over the coming century using species distribution modeling and ocean circulation simulations. Researchers built an ensemble of habitat suitability models using historical climate data and end-of-century climate projections to identify coastal wetlands likely to become suitable as winter temperatures warm.
They then simulated how floating mangrove propagules move in real ocean currents to determine whether those newly suitable areas are actually reachable from existing mangrove populations. They also examined historical hurricane tracks to assess how major storms might help transport propagules farther north. Together, these methods link climatic suitability with ocean connectivity to assess realistic range expansion potential.
The results suggest that warming temperatures will continue to push suitable mangrove habitat northward beyond the current range limit in northeastern Florida, potentially into coastal Georgia and, under higher emissions scenarios, toward South Carolina by 2100.
Importantly, the study highlights that range expansion depends not only on climate but also on connectivity. Ocean currents can transport buoyant mangrove propagules northward from established populations, allowing new wetlands to be colonized when conditions become favorable. Hurricanes may further enhance this process by moving propagules long distances during peak dispersal season. Together, warming temperatures and strong along-coast connectivity create conditions that make continued mangrove expansion likely.
These projections offer a forward-looking lens on coastal change for managers and stakeholders. Identifying wetlands that are both climatically suitable and connected to existing mangrove populations can help guide restoration investments, land acquisition, and habitat management strategies. In some places, managers may choose to facilitate mangrove expansion to enhance carbon storage and storm protection. In others, they may prioritize conserving open salt marsh habitat for species that depend on it.
The research underscores that coastal conservation must account for habitat transformation, not just habitat loss. Integrating climate projections with connectivity analysis provides a more realistic foundation for planning in dynamic coastal corridors, where the balance between mangroves and marshes will continue to evolve over time.
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