Tidal wetlands are hard-working but often-overlooked ecosystems. They undergird fisheries and provide key habitat for birds; lock in carbon; and serve as the coast’s frontline of defense from flooding and storms. But now wetlands need protection themselves.
Rising sea levels threaten the future of tidal wetlands, which must move further inland or drown. It’s a hidden problem that will become more visible and urgent over the next few decades, said Christine Shepard, Director of Science for The Nature Conservancy’s Gulf Program.
“It’s critically important to ensure that we have a future that includes marshes and mangroves and the benefits they provide,” Shepard said. “In talking to our partners across the Gulf Coast, we have found that most conservation groups are really not accounting for this in their planning.”
A new team, co-led by Shepard and funded by the Science for Nature and People Partnership, or SNAPP, aims to change that.
The Future Tidal Wetlands working group – an interdisciplinary team of scientists, engineers, conservation experts and land managers – is developing detailed maps of how sea-level rise will reshape the Gulf Coast and identifying potential corridors for today’s wetlands to retreat landward.
This tool will enable government agencies, land managers and other conservation decision-makers in Florida, Alabama, Mississippi, Louisiana and Texas to better select and prioritize areas to reserve for future wetlands and manage wetland migration when necessary.
“Being able to look at predicted climate models, especially when you’re talking about permanent land protection, is paramount,” said Vance Crain, executive director of the Partnership for Gulf Coast Land Conservation and a co-principal investigator of the working group with Shepard and Steven Scyphers of the University of South Alabama. “We’re really concerned about what the landscape is going to look like in 20 to 50 years, and this tool [will help] us answer that question.”
The group is part of SNAPP’s inaugural Innovation Hub, a joint effort with TNC, the Wildlife Conservation Society and the Doris Duke Foundation to develop strategies for a more nature-positive future in the U.S.
Preserving the unsung heroes of coastal defense
Tidal wetlands, which include salt marshes, swamps, deltas and mangrove forests, make up a fraction of land area, but they have an outsized impact on coastal resilience. These shallow-water ecosystems provide an estimated $23 billion in annual storm protection for U.S. coastal communities.
As they rapidly vanish due to drainage and fill for development, as well as rising sea levels, the coastline is left vulnerable. One study estimated that the amount of Florida wetlands lost from 1996 to 2016 resulted in an additional $430 million in property damage in 2017’s Hurricane Irma.
“Coastal habitats, especially wetlands, are really the sponges that protect us from all the scary things that the water can do,” said Katie Sperry, SNAPP Research Fellow for the Future Tidal Wetlands working group.
But with climate change, these shallow-water ecosystems are often trapped between waterfront infrastructure and an encroaching ocean, a phenomenon known as coastal squeeze.
“Marshes can’t migrate onto a parking lot,” Sperry said.
This is where the group’s maps can help. Sperry is leading efforts to generate Gulf Coast maps of future climate scenarios that will include data on factors such as development pressure, timelines of when wetlands must move, socioeconomic information and places where conserving land for wetlands could provide added benefits, such as increasing access to recreational fishing or kayaking.
“It’s weird to talk about the conservation of a habitat that doesn’t exist yet,” Sperry said. “But what these maps will enable us to do is look at an existing salt marsh and say, given sea level rise, this is where we think this marsh is going to go.”
She is also working on identifying tipping points – when and where wetland migration may be most pressing. Sea level rise is not always gradual: Hurricanes and other major storms can bring sudden, dramatic changes to the coast.
“We’re not even sure, based on the science we have right now, that all marshes and mangroves will be able to move inland fast enough to keep up with sea level rise,” Shepard said. “Part of the SNAPP science grant is to explore what we know about the landward migration of wetlands and how we can use this information to pick the best areas to protect their migration space.”
Rising sea levels also threaten the marsh buffers that protect valuable farmland and development on the coast, said Will Collins, a NOAA Digital Coast Fellow with TNC who will facilitate the implementation of the SNAPP maps.
“So much of our coastal economic systems rely on marshes, and now we have the ocean pushing inward,” Collins said. “If we don’t actually think about this and strategize, there will be areas that just become entirely inundated. The idea is that we can be the stewards of the coast – and that we should be.”
The group’s work will kickstart TNC’s Restoration, Adaptive Management, and Protection for Future Wetlands (RAMP for Wetlands), a Gulf-wide project managed by Collins that focuses on protecting and managing marsh migration corridor space.
Inviting the maps’ target users into the mapmaking process
One of the Future Tidal Wetlands group’s goals is to make their new Gulf Coast maps as simple and effective as possible for the people making conservation decisions on the ground. To ensure the maps are actionable, those decision-makers are part of the group creating them.
One such decision-maker is Crain, who leads a nonprofit coalition that helps strategically increase the conservation of Gulf lands and waters through easements and acquisitions.
“One of the benefits of working with SNAPP is that we get to have those conversations as the tools are developed,” Crain said. “The aim here is that we can go in more collectively with the science folks and the researchers to build this thing out where it’s going to be really helpful to the entire conservation community.”
For scientists such as Shepard, perspectives like Crain’s are invaluable. “Our team really benefited from having the real-life people that will do this work in the room to point out, okay, that assumption you have is incorrect, or that’s not how this works,” she said. “It was so grounding.”
The group aims to have its maps ready for use by December 2026. Shepard sees the project as a foundation that could grow into a Gulf Coast counterpart to the South Atlantic Salt Marsh Initiative.
“We’re really looking to elevate this issue across the Gulf region,” Shepard said. “Having a clear understanding of where the opportunities are is key and having that those maps be based on the latest science is essential.”
