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Why salt marsh growth on the US East Coast is good news in the fight against climate change

Updated: Sep 22, 2023

Introduction: How Salt Marshes are Becoming a Critical Tool in Fighting Climate Change

Salt marshes are some of the most important ecosystems on the planet, providing essential benefits like carbon storage, water filtration, and erosion control. These wetlands are also home to a wide variety of plant and animal species that rely on them for survival. However, salt marshes are under threat from a changing climate, and rising sea levels are putting them at risk of disappearing altogether.

The Marsh Race: Can Salt Marshes Keep Up with Rising Sea Levels?

Scientists have been wondering whether it's possible for salt marshes to keep up with rising sea levels, and a new study has shed some light on the issue. The study, which was published in Earth's Future, is the first to assess the rate of soil accretion in salt marshes on a large scale, comparing soil core from nine salt marshes from Maine to Georgia.

A Century-Long Soil Accretion Study: Revealing How Salt Marshes Have Responded to Change

The dark, peaty columns used in the study record over 100 years of the marshes' histories, and researchers dated the soil to calculate how quickly the wetlands grew over time and how that rate changed. The findings were exciting, showing that soil accretion has sped up in all nine marshes, and six of them built soil at roughly the same rate as sea level rise over the past century.

Factors Affecting Soil Accretion Rates: Why Some Salt Marshes Are Keeping Up, and Others Are Not

So, what factors affect how quickly a salt marsh accumulates soil? Two main factors come into play: how much sediment is deposited in the wetland during tidal floods, and how much organic matter from the marsh's plants escapes decomposition. Cooler temperatures let more organic matter build up.

If sea level is rising slowly, sediment is plentiful, and vegetation is booming, a coastal wetland can keep pace with rising waters. But if sea level rises too quickly, that balance is lost. Three marshes in North Carolina, South Carolina, and Virginia could not keep up with local sea level rise due to low sediment supplies from damming and warmer temperatures.

The Living Shorelines Solution: Installing Vegetation to Retain Sediment and Slow Seawater Inundation

To slow the process of seawater inundation, communities could install "living shorelines" of vegetation to retain sediment, said Molly Keogh, a coastal geologist at the University of Oregon who was not involved in the study. These natural barriers can help protect coastlines from erosion, reduce flooding, and provide habitat for wildlife.

Conclusion: Why Preserving Salt Marshes is Crucial in Our Fight Against Climate Change

The findings of this study are encouraging, showing that many coastal salt marshes around the world may be accelerating their growth. However, it's important to remember that not all salt marshes are created equal, and some are at greater risk than others. Preserving salt marshes and protecting them from the impacts of climate change is crucial in our fight against this global crisis. By understanding how these ecosystems work, we can work to protect them and ensure that they continue to provide essential benefits for generations to come.

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