Over 90% of salt marshes at risk from sea level rise: Study

Cape Cod's salt marshes are not only visually stunning but also incredibly important, serving as one of the most productive ecosystems on the planet.

These wetlands are vital in cycling nitrogen, sequestering carbon, protecting coastal development from storm surges, and providing habitats and nurseries for countless fish, shellfish, and shorebirds.

According to a study published in the journal Science of The Total Environment on March 28, 2023, increased nitrogen levels lead to higher vegetation and marsh surface accretion.

However, a recent study by the Marine Biological Laboratory (MBL) predicts that more than 90 percent of the world's salt marshes will be submerged by the end of the century.

The study spanned 50 years and was conducted at the Great Sippewissett Marsh in Falmouth, Massachusetts, by scientists at the MBL Ecosystems Center.

The team examined whether increased levels of nitrogen in the environment would affect marsh grass species by mapping vegetation cover in experimental plots.

Due to the length of the study, the researchers were also able to detect the effects of climate change on the ecosystem, especially those resulting from rising sea levels.

Salt marshes face threats from sea-level rise

The study found that the increase in nitrogen favored higher levels of vegetation and accretion of the marsh surface, but unfortunately, regardless of the concentration of nitrogen applied to the marsh, the ecosystem will not be able to keep up with the submergence caused by the global rise in sea level.

Rising sea levels and human development are causing "coastal squeeze" in salt marshes around the world, with barriers such as dikes and buildings obstructing natural migration to higher ground.

Sea level rise is also accelerating, making it difficult for mudflats to keep up. The only solution for bog plants in this scenario is to colonize new areas or move uphill, but this may be impossible in some places.

According to MBL scientist Javier Lloret, sea level rise is the most significant threat to marshes, and measures must be taken to prevent or adapt to losses and maintain the important roles these ecosystems play for nature and humans.

Half a Century of Science

The long-term data set at Great Sippewissett Marsh has given scientists valuable information about the impact of global sea level rise, which was not initially considered when the experiment began in 1971.

Long-term data sets allow scientists to Investigators set benchmarks for problems that may arise in the future. Ecological changes occur on much longer time scales compared to other biological systems, and understanding these changes requires a long-term perspective spanning decades or even centuries.

As Javier Lloret explains, studying an entire ecosystem requires thinking beyond short-term changes and considering the big picture over long periods.

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