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Salt marshes are
intertidal habitats formed by communities of salt-tolerant grasses, herbs, and
low shrubs that improve overall water quality and support both marine and
Found from arctic to subtropical climates, salt marshes export carbon and energy into the water column, store carbon in their root systems and sediments, and filter nutrients, pollutants and pathogens from water along global coastlines. Salt marshes also help to protect against storm damage, flooding and erosion.
Salt marsh habitats can be damaged or destroyed by human activities, including oil spills, agricultural drainage, and development. Climate change and sea level rise also threaten salt marshes, particularly if natural features or human developments prevent their landward retreat.
How Was It Measured?
Data on the area of
salt marsh habitats for each country come from multiple sources (Bridgham et
al. 2006; EEA Eionet 2008; Environment New Zealand 2007; JNCC 2004), and are
generally reported in km2.
The status of salt marsh related ecosystems and approximate rates of current
salt marsh loss were calculated from previous extent and current extent numbers
Trend for salt marshes received a categorical score. A score of 0.5, 0, or -0.5 was given for an increasing, decreasing, or stable trend respectively. Based on the trend of the habitat, the salt marsh was also assigned a condition score. If the trend was stable or increasing, it was assigned a condition score of 1.0, and if the trend was decreasing, it was assigned a condition score of 0.5.
Like all of the habitats used in the OHI, salt marsh habitat is used as a component in calculating scores for many of the different goals. However, it is used differently depending on the goal in question. Although habitats such as salt marshes are used in calculating these goal scores, countries are not penalized for not having a certain habitat type. Calculations are based on the rank of existing habitats, as opposed to using all possible habitat types.
Salt Marsh habitat was used as a component in calculating scores for Coastal Protection, Carbon Storage, and Biodiversity (Subgoal: Habitat). The salt marsh component is used to calculate Trend and Status in these goals, however calculations differ slightly by goal.
What Are The Impacts?
Salt marshes diffuse
the impact of storms by reducing wave heights, thereby helping to protect
shoreline ecosystems against damage.
Wave heights can be reduced by up to 50% over the first 10-20m of vegetated salt marsh surface (Moller et al. 2006).
Salt marshes store carbon in their surface deposit soil. When salt marshes are exposed to erosion or submersion, CO2 is released from these stored deposits back into the atmosphere.
The surface sediments of salt marshes can contain as much as 10-15% carbon (Savidge and Blanton 2011) [Approx. 430 ± 30 Tg C (Chmura 2003)].
The destruction or drainage of salt marshes can lead to the subsequent invasion of nonnative species which deplete existing species and grasses beneficial to the native marine and wildlife population.
Salt marshes provide the breeding grounds for a number of species, helping to maintain coastal biodiversity in both salt and freshwater ecosystems.
HUMAN HEALTH IMPACT
Salt marshes improve
water quality by removing pathogens and pollutants from natural wastewater
before they reach estuaries and coastal waters and by transporting key
nutrients between water and land ecosystems.
Salt marshes are
important spawning grounds for many fish species. These coastal habitats have a
direct correlation to the amount of commercial fish harvested annually.
What Has Been Done?
Vulnerable to storm
surges and coastal flooding, coastal communities along the North Sea Basin
sought a long-term alternative to costly and continual repairs to sea walls
along their shores by implementing salt marsh restoration.
Get More Information
Ramsar Convention on Wetlands
represents an agreement between member states to protect and preserve wetland
ecosystems within a nation’s boundaries and provides a Guide for Policy Makers
This organization is
committed to sustaining and restoring wetlands while protecting their
biodiversity and natural resources.
Saltmarsh Management Manual (DEFRA)
information, guidance, and techniques to manage, restore, and enhance salt
Connor, R. F., Chmura, G. L. & Beecher, C. B. Carbon accumulation in bay of fundy salt marshes: Implications for restoration of reclaimed marshes. Global Biogeochemical Cycles 15, 943–954 (2001).
Giblin, A. E., Luther III, G. W. & Valiela, I. Trace metal solubility in salt marsh sediments contaminated with sewage sludge. Estuarine, Coastal and Shelf Science 23, 477–498 (1986).
Kennedy, Victor, Twilley, Robert, Kleypas, Joan, Cowan, James & Hare, Steven Coastal and Marine Ecosystems & Global Climate Change: Potential Effects on U.S. Resources | Center for Climate and Energy Solutions. (2002)
Koch, E. W. et al. Non-linearity in ecosystem services: temporal and spatial variability in coastal protection. Frontiers in Ecology and the Environment 7, 29–37 (2009).
Möller, I., Spencer, T., French, J. R., Leggett, D. J. & Dixon, M. Wave Transformation Over Salt Marshes: A Field and Numerical Modelling Study from North Norfolk, England. Estuarine, Coastal and Shelf Science 49, 411–426 (1999).
Savidge W and Blanton J (2011). Urban Runoff and Oxygen
Dynamics on Salt Marsh Platforms. Skidaway Institute of Oceanography: CIG Final
Report for Year 2 Teal J and Howes B (2002). Salt Marsh Values:
Retrospection from the end of the Century. Concepts and Controversies in Tidal
Marsh Ecology: Part 1, 9-19.
Valiela I, Cole M, Mcclelland J, Hauxwell J, Cebrian J,
Joye S (2002) Role of Salt Marshes as Part of Coastal Landscapes. Printed in:
Weinstein M and Kreeger D (Eds) (2002). Concepts and Controversies in Tidal
Marsh Ecology. Kluwer Academic Publishers: Dodrecht, The Netherlands
Vernberg, F. J. Salt-marsh processes: A Review. Environmental Toxicology and Chemistry 12, 2167–2195 (1993).