Marshes and mangroves Flashcards
Kirwan et al, 2016
- Occur at interface…
Kirwan and Megonical, 2013
- Importance
- In order to survive
- What they do
Leonardi and Fagherazzi, 2014
- Very resilient…
Temmerman et al, 2013
- Reclamation- wetland cut off (sediment deposition. land rise reduced)
Faherazzi, 2014
- Biggest threat
- More vulnerable recently…
What are saltmarshes?
Salt marshes are coastal wetlands that are flooded and drained by salt water brought in by the tides.
They are marshy because the soil may be composed of deep mud and peat.
Peat is made of decomposing plant matter that is often several feet thick.
Peat is waterlogged, root-filled, and very spongy.
Saltmarsh formation
The formation begins as tidal flats gain elevation relative to sea level by sediment accretion, and subsequently the rate and duration of tidal flooding decreases so that vegetation can colonize on the exposed surface.
Factors Affecting Salt Marsh Development
Weather: storms can erode the marsh
River regime: changes in currents and volume can affect erosion.
Wave type: changes in direction, nature and size can affect marsh stability
Sediment supply: supply changes can enhance or diminish the available silt
Human action: commercial, industrial and recreational activity can damage marsh
Sea level: rises can upset equilibrium and destroy the marshes
Climate: affects species types, growth rates and sea levels
Tidal regime: changes in tidal currents can increase erosion and alter species
What do plants undergo in saltmarsh progression?
The plant community then undergoes a series of changes known as a succession.
The initial low energy environment can result from many causes. The most common are:
the protection from the open sea provided in the inner reaches of estuaries and rias.
the protection offered by spits, bars or other coastal landforms.
Human threats to the Salt Marshes
Industrial pollution e.g oil pollution in the Solent has contributed to the decline of Spartina.
Agricultural eutrophication
Dredging removes sediment
Commercial and recreational shipping and water sports activities, such as jet-skiing, cause “wash”. This can erode marshes already vulnerable to vegetation “dieback”.
Grazing = trampling
Reclamation makes tidal areas narrower. This means there is less space in which energy can dissipate. This can create increased erosion.
Natural threats
Sea levels may rise too quickly for the marshes to adjust. Increased incidence of storms leads to increased flooding.
Storms create greater wave energy and more potential erosion and may lead to a loss of sediment supply.
Changing temperatures and rainfall patterns may affect the tolerance of the marsh species - this has been suggested as one reason for the decline in Spartina.
The loss of salt marshes for whatever reason is likely to have serious consequences.
Modifications to river hydraulics and coastal wave patterns are likely to lead to increased marine energy in other parts of the coastal system. These may be natural features such as unprotected coast or sea walls and other sea defences. These may become vulnerable to breaching and inundation.
There will also be a loss of habitat and biodiversity. This may affect spawning grounds and the fisheries and shell-fisheries that depend on them.
There will also be a loss of amenity and recreational opportunities such as bird watching or experiencing a wilderness environment.
