Earth Science: Origins and Geology – Saltwater Wetlands
The term wetland is used to describe a range of habitats that are entirely submerged or partially permeated by water. There are freshwater and saltwater wetlands. In all of these habitats, the site where the water meets the land is always shifting.
Saltwater wetlands are located at the frontier between ocean and mainland. At these locations, saltwater from the ocean mixes with freshwater from rivers. This mixture creates a particular challenge for the plant and animal worlds, which are normally adapted to either one habitat or the other.
While the number of species in general is usually low, the number of individuals of a particular species can be very high. On many flat coastal areas where rivers empty into the ocean, embankments are formed by oceanic currents and tides, as well as the sediment carried by the rivers. At the mouth of the Rhone in France, for instance, lies a motley mosaic of habitats, such as brackish water lakes, moist swamps, riparian forests, beaches, sand dunes, and salt marshes.
Coastal areas with strong tides feature a transitional zone between the mainland and the ocean: the tidal flats. The ocean washes over this area at high tide and it dries up again at low tide. Only rarely does the water reach the salt marshes at higher elevations where glasswort or cordgrass grow. True intertidal mudflats can only be found on the northwest coast of Europe and on the west coast of South Korea.
However, similar conditions also exist on the east coast of North America. This unique ecosystem forms a habitat for worms, mussels, and snails. It is also a paradise for millions of migratory birds.
Mangrove swamps
Mangrove swamps are located in the tidal regions on tropical coasts and at the edges of broad estuaries. Various mangrove tree and shrub species are the only woody plants that have a tolerance for salt. At high tide, often only the tree crowns can be seen above the waterline; at low tide an entanglement of roots appears, providing a habitat for mudskippers and fiddler crabs.
Mangrove stocks worldwide are extremely endangered. In eastern Africa, they are used for firewood. When mangroves are removed, the protection they provide against unusually high tides is also lost.
THE EVERGLADES
This unique subtropical wilderness, which the Native Americans of the region called “grassy water,” extends across the southern tip of Florida. What looks like a large group of lakes is actually a river fed by Lake Okeechobee, which is 50 miles wide, but only a few inches deep.
Certain parts of this mosaic of swamp grass, marsh- lands, cypress forest, and mangrove swamps are under protection. It is home to the Mississippi alligator and the Florida manatee.