Along temperate coasts, the effects of climate change—including sea-level rise, erosion, and more frequent and stronger storms—are threatening a vital habitat that offers one of the best natural defenses against those perils.
Salt marshes are low-lying ecosystems characterized by salt-tolerant shrubs, herbs, and grasses that not only protect coastal communities but also provide vital habitat for fish, birds, invertebrates, bivalves, and other wildlife. In the United States alone, up to 75% of commercially important marine species, including shrimp, crabs, and finfish, rely on this ecosystem. That rich biodiversity supports coastal communities and their businesses, from commercial and recreational fishing fleets to seafood markets and tourism outfitters.
Along with other coastal wetlands—namely mangroves and seagrass—salt marshes play a significant role in helping communities adapt to and mitigate the impacts of climate change. This habitat provides flood protection and shoreline stabilization by buffering coastal communities from the full impact of storms, which in many areas have become more frequent and intense. In the U.S., coastal wetlands are estimated to provide the equivalent of $23.2 billion in storm damage protection per year.
Another major benefit: Blue carbon
Marshes also have extraordinary capacity to sequester carbon in their underlying soil, and this carbon can remain stored for decades if it is undisturbed. In fact, the saturated soil found in marsh ecosystems can retain more carbon per acre than some terrestrial forests and is often referred to as blue carbon—that is, carbon captured and retained by ocean and coastal ecosystems.
Salt marshes are one of only three marine ecosystems—along with mangroves and seagrass—currently recognized by the Intergovernmental Panel on Climate Change for their measurable carbon benefits. And scientists and stakeholders alike note the “triple-win” effect that healthy, intact salt marshes convey by helping governments address climate change through mitigation, adaption, and resilience.
Salt marshes are threatened, however, by the very phenomena that they can help to alleviate. Experts estimate that 50% of salt marshes have been lost globally, with declines continuing because of climate change, coastal development, industrialization, and pollution.
But there is hope to reverse this trend. Governments and international bodies are pursuing concrete ways to protect and restore salt marshes and the benefits they provide, such as climate policy instruments like the Paris Agreement. Parties to the agreement may include efforts to protect and restore salt marshes in their domestic climate action plans, called nationally determined contributions (NDCs). Every party to the Paris Agreement was due to enhance its NDC in 2020 and will submit further revisions—each with increasing ambition—every five years.
In the U.S., salt marsh and other blue carbon habitats can be incorporated into state plans for using nature-based solutions to reduce greenhouse gas emissions, known as natural and working lands strategies. By quantifying the amount of carbon stored in these habitats and then setting goals to protect and expand that storage through conservation and restoration, states can help to support broader efforts to mitigate climate impacts. In addition, states, in partnership with federal agencies, should advance regional, landscape-level strategies to help salt marshes better adapt to climate impacts.
Salt marshes are an important nature-based solution in the fight against climate change, with far-reaching benefits for communities, wildlife, and coastal economies. Protecting these vital habitats must be a policy priority—globally and at all levels of government—moving forward.
Stacy Baez works on The Pew Charitable Trusts’ coastal wetlands and coral reefs project, and Sylvia Troost works on Pew’s conserving marine life in the United States project.