High Tides, Higher Stakes - Salt Marshes (Transcript)
- Ava Lee
- Mar 23, 2025
- 3 min read
Updated: Apr 14, 2025
Presented by Ava Shields on Tuesday, the 18th of March in 2025. Part of the Conference
A salt marsh is a specific type defined by its geological location. It is an area that experiences flooding and drainage near low coastal wetlands, in places such as estuaries and deltas. While some marshes form in desert-like-arid regions where flooding is occasional, salt marshes receive frequent flooding and drainage because of tides from the salt or where the freshwater meets salt water (brackish water). A key characteristic of salt marshes is their vegetation inhabitants known as halophytes, these plants have evolved to tolerate and even thrive in saline conditions.
Salt marshes (tidal or coastal marshes and intertidal zones depending on the context) can be found worldwide, particularly in middle to high latitudes. They cover almost 5.5 million hectares of the world, and 30% of all tidal marshes form in the U.S. Other places include Europe, China, and Australia.
Their inhabitants vary based on region; however, this ecosystem serves as a shelter, nesting grounds for migratory birds, filtration systems from runoff, and carbon sinks. Species such as the fiddler crabs and periwinkle snails are considered keystone species. Fiddler crabs aerate the soil through their burrowing activities, which promotes plant growth and nutrient cycle. Periwinkle snails graze on algae, which helps maintain the balance of a marsh ecosystem.
Source: Mungfali.com Saltwater Food Web
Similar to a Peatbog, you may find peat in salt marshes. The soil there can be composed of deep mud. Because many marshes are located along the shoreline, the tides bring sediment which is filtered by the adapted plants. This sediment floats to the bottom, accumulating and elevating the marshes. Submersion of tides and containing a lot of decomposing plant material, oxygen levels are low - hypoxia.
Without the grasses, significant impacts on the entire ecosystem will occur. When we think of keystone species we often think of mammals, but in reality, keystone species expands to just about everything, from microorganisms to plants. Without grasses, such as the cordgrass (spartina), soil erosion, loss of habitat, disrupted food chains, reduced water quality, and carbon storage loss can occur.
Furthermore, there are many threats coastal marshes face, including being drained for agricultural purposes, salt extraction, and complete submersion from rising sea levels. The increasing intensity and frequency of storm events cause what scientists label as “Coastal Squeeze”. Because the ocean levels absorb 25-31% of the world’s carbon dioxide, the energy is turned into heat, causing water molecules to expand. When the ocean temperature increases, tsunamis are more likely to occur.
Salt marshes are a natural barrier to flooding, reducing damage by up to 20% during storms. However, if threatened, they move further inland, however, since marshes are primarily located on the coast, there are sea walls to protect residential areas from tsunamis. Thus, marshes cannot creep any further since the wall is physically preventing them.
This creates a major problem because salt marshes are home to a diverse ray of species. There are fish, plants, and invertebrates.
Okay Ava, well you did mention that marshes can theoretically grow. Yes, I did say that! Thank you so much for paying attention. If there is anything we should take away from this class or more specifically this unit is that anthropogenic climate change has changed the speed at which nature occurs. The accumulation of an elevated mud flat for a marsh takes years while ocean level rising takes months. So, the sea level outpaces the accumulation of sentiment.
So, what can we do? While terminating the use of fossil fuel is highly unlikely, we could implement a gap in current sea walls to reflood previously reclaimed land to reconnect the tidal flow or create lagoons by raising the land.
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