A wetland can be classified as an area that is relatively flat, aids in slowing down water movement, and which has temporarily, seasonally, or permanently saturated soils. Where rivers meet the sea, unique environments, called estuaries, are formed. These estuaries are constantly altered due to tidal action, floods, temperature variation and (depending on the system) periodic closure of the river mouth. This results in a variation of salinity (within estuaries) due to the mixing of sea water with fresh river water. Not all wetlands end in an estuary.
Saltmarshes are found on the landward side of mud and sand flats in the upper tidal zone of calm coastal waters, such as sheltered bays, river mouths and estuaries. Saltmarshes are formed on the perimeter of certain estuaries and lagoons. The plants found here have to withstand salinities of up to 3 times that of seawater. This results in a low species diversity in saltmarshes.
With an influx of nutrients from both the river and sea, estuaries and the accompanying wetland are highly productive systems that form the habitat of a diverse number of flora and fauna. Their functioning as nursery sites are of particular importance to many aquatic species. Plants that are adapted to wetland conditions act as sponges, helping to slow down water flow and reducing the effects of floods . Water is released slower from these areas, which means it will be available for longer. Less water is lost through evaporation due to the cover provided by wetland vegetation. They act as natural filters that help to purify the water by trapping silt, pollutants, excess nutrients, heavy metals and pesticides.
Wetlands have been extensively used as grazing land for livestock and are a good source for reeds that are used for basket weaving, thatching and hut construction. They are perfect fishing and hunting grounds and also provide an opportunity to observe birds from bird hides or along hiking trails. Canoeing, swimming or just picnicking in the area are some of the other activities that wetlands lend themselves to. However, certain activities are detrimental to the healthy functioning of wetlands.
This include excessive removal of vegetation in catchments, increased exotic plantations, bad agricultural practices, draining and filling-in of wetlands , obstruction of natural water flow through the building of causeways , waste water, effluent and excess nutrients seeping into catchment water as well as excessive water abstraction from rivers.
We all benefit from healthy wetlands directly or indirectly. By understanding and appreciating the functioning of the system one is able to, through sensible and simple practices, help protect our remaining wetlands. Influence those around you with your acquired knowledge of wetlands (refer them to this website). Stop damaging activities - illegal dumping or pollution spills - higher up in the catchment area which manifest themselves in the lower parts. Do not disturb wetlands or overfish. This causes important species numbers to dwindle.