Q&A: What Is the Future for New Jersey’s Coastal Marshes? | Article

Coastal marshes are under stress from climate change and coastal development. Yet these ecosystems are incredibly important in protecting coastal populations and enhancing the ability of coastal communities to absorb climate shocks. Judith Weis—a marine biologist, coastal marsh expert, and former Congressional American Association for the Advancement of Science fellow—discussed the challenges facing coastal marshes in a recent interview with EESI. Weis, a professor emerita of biological sciences at Rutgers University, chairs the Science Advisory Board of New Jersey’s Department of Environmental Protection and shared insights from their coastal marsh recommendations. These findings were also turned into a journal article that came out last fall.

EESI: How are coastal marshes being impacted by sea level rise?

Weis: Marsh plants are adapted to being underwater part of the time, but they are not adapted to being underwater all the time. Because sea levels are rising faster, our marshes are in trouble. Marsh edges are moving back, so they are losing acreage. Also, they are not increasing their elevation as fast as sea level rise, so the water is not going fully off some marshes at low tide like it is supposed to. As a result, we are seeing pools forming where there is no grass on the marsh because it gets waterlogged and grasses die.

EESI: How is New Jersey approaching this challenge?

Judith Weis in a marsh. Photo courtesy of Judith

Weis: There are four remedies we talk about in the New Jersey Department of Environmental Protection Science Advisory Board’s coastal marsh recommendations: migration pathways, changing management of Phragmites, living shorelines, and thin layer deposition.

EESI: Let’s jump into each of those recommendations. What are migration pathways for marshes?

Weis: If a marsh cannot keep up vertically with sea level rise, meaning it cannot stay above the low-tide water level, another option is for the marsh to migrate inland into what had been open land or forest behind it. In much of New Jersey, this is a problem because it is a very developed state. There are usually roads, houses, and other infrastructure in the way of a marsh’s migration path. So, the idea of migration pathways is to clear out what is behind the marsh so it can move inland.

If there are homes behind a marsh, you are dealing with homeowners whose homes are probably flooded very often. These people are in danger, so a lot of them are already open to moving. There is a state government program in New Jersey called Blue Acres, which will buy out homeowners in that situation. This program will probably have to be expanded in the future as sea levels continue to rise and the flooding gets worse.

To learn more about marsh migration and buyout programs, watch EESI’s briefing Living With Climate Change: Sea Level Rise.

EESI: The next recommendation is about the invasive plant, Phragmites (a.k.a., the Central European common reed). What challenges and opportunities does this coastal species present?

Weis: Like many invasive species, Phragmites australis has out-competed the local plants. In New Jersey, many people have tried to eradicate Phragmites to clear the way for native plants to re-populate the area, but in many cases, the Phragmites returns within a decade or so and they have to do it again.

But there is an important and under-appreciated role of this reed. Our research findings show that Phragmites help marshes get higher elevation faster than native species, which is important as sea levels rise. Phragmites also absorb more carbon dioxide from the atmosphere than native plant species, which means this plant species is helping to mitigate climate change. It does a variety of other beneficial things. Living things are not good or bad. They are not heroes or villains. The “Big Bad Wolf” eats things you might be sympathetic to, but in this case, it performs vital “ecosystem services.” So, we have to look at things in a different way and change management of the reed. We suggest finding ways to keep some of these plants on the marsh to help it keep up with sea level rise.

EESI: The third recommendation focuses on living shorelines. What are living shorelines and what is their role in addressing sea level rise?

Weis: A lot of marshes are losing acreage due to their edges eroding. In many parts of the state, areas that once were marshes are now open water. So, if you were to put something harder, like an oyster reef, in front of the marsh edge, it would buffer the currents and the waves that are eroding the edge. This is called a living shoreline. Living shorelines are currently being experimented with in southern New Jersey. They are quite effective. One of the lessons being learned, though, is there is no one-size-fits-all solution for coastal marshes. You have to know your site and be prepared to monitor and modify what you are doing if things are not working.

Graphic from EESI's 2020 article "Living Shorelines Protect Coasts but Better Permitting Regulations Are Needed" written by Sydney O'Shaughnessy.

To learn more about living shorelines, watch EESI’s briefing Coastal Resilience in the Southeast: Science, Policies, and Programs Furthering Local Resilience Goals and read the article “Living Shorelines Protect Coasts but Better Permitting Regulations Are Needed.”

EESI: The final recommendation is on thin layer deposition. Can you describe this practice and how it can support coastal marshes?

Weis: Thin layer deposition is a practice where you take sediment from creeks and from the bottom of the bay and spray it on top of the marsh. This elevates the surface of the marsh that was not keeping up with sea level rise. Basically, you are artificially making the marsh higher. The type of sediment is important. Regular sand will not work. You need a muddier type of sediment that is generally found in marsh creeks. By putting all that sediment there, you do kill the grasses that are growing, but in another year or two, they will come back. To expedite the process, after you have put several inches of new sediment on the top of the marsh, you can then plant new grasses on top. This is another practice being experimented with in New Jersey and elsewhere. The results thus far are promising.

To learn more about thin layer deposition, watch EESI’s briefing Ports Leading the Way on Mitigation and Resilience.

This interview was edited for length and clarity.

To read more about Judith Weis’s work and her involvement with EESI, check out the June 2022 edition of EESI Impact.

Authors: Tim Slattery and Susan Williams