Research published in the American Geophysical Union science journal Earth’s Future indicates that 84% of coastal wetlands in the U.S. are gradually being overtaken by rising seas. According to a 14-member study headed by Duke University wetland ecologist Justine Neville, many of these wetland areas will become entirely submerged if mitigating action is not taken.
US Coastal Wetlands Face Submergence Risk From Rising Seas
While wetland vegetation thrives in water and increased sea levels have boosted wetland growth to an extent, researchers explain that excess hydration can turn lethal. Glenn Guntenspergen, a researcher working for the U.S. Geological Survey in Maryland, noted that coastal plants have optimum ranges, but excessive flooding causes the system to shut down, leading to decreased production and eventual death.
Vulnerability Across Coastal Regions
The study took an expanded nationwide approach compared to past wetland research that was largely limited to localized fieldwork. Neville’s team collected data from hundreds of sites along the Atlantic, Gulf, and Pacific coasts.
The research points to the Gulf Coast as an especially high-risk region. While 89% of U.S. coastal wetlands are slowly climbing in elevation due to growing sediment layers, 73% of those areas are not rising fast enough to avoid future submergence without human intervention. Atlantic and Pacific coastal biomes are considered less vulnerable than Gulf Coast wetlands, a difference Neville attributed to the Southern region’s heavy historical shipping traffic and fossil fuel extraction.
Saltwater Intrusion and Broader Impacts
Beyond physical submergence, the landward movement of seawater poses growing threats to drinking water supplies, coastal farming, and coastal ecosystems. On Louisiana’s Gulf coast, which was hit by a record five hurricanes or tropical storms, Native American tribes requested United Nations assistance to force U.S. government action against climate-forced displacement.
Tribes reported that saltwater has poisoned their land, crops, and medicinal plants, stripping them of income and the ability to feed themselves healthy food, according to Shirell Parfait-Dardar, chief of the Grand Caillou/Dulac Band of Biloxi-Chitimacha-Choctaw.
Research documented by Marcelo Ardon, a North Carolina State University ecologist and biogeochemistry expert, shows that saltwater intrusion is happening right now rather than decades in the future. Findings indicate that:
- Thousands of acres of farmland have gone out of production due to ruinous salt properties.
- Public aquifers and private wells face increasing threats, with coastal utilities closely monitoring salinity and seeking new water sources.
- “Ghost forests” of dead and dying trees are spreading along coastlines from New Jersey to the Gulf of Mexico.
As Cnsmaryland reports, the diminishing of coastal wetlands would also deal a severe blow to endangered species such as the Gulf sturgeon and leatherback sea turtle.
Mitigation and Conservation Efforts
Despite the risks, Neville noted that the outlook is not entirely bleak, as around 70% of studied wetlands could potentially grow further inland and avoid anthropogenically induced death by drowning. Ecologists and conservationists will need to take action by balancing sediment levels, ridding wetlands of manmade features like dikes, and protecting adjacent inland areas from development to provide a path of retreat.
Conservation acquisitions are already underway in some regions. For example, the Blackwater National Wildlife Refuge in southern Maryland acquired over 3,000 acres for marsh migration, highlighting the ongoing efforts to protect sensitive coastal lands.