WETLANDS

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Human Activities and Wetlands

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.

These 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.

BIRDS

A variety of food sources are available to birds frequenting wetlands. these range from algae, fish. frogs. worms, crustacean, molluscs, insects and crabs. Species such as ducks, coots, waders, otster catchers, cormorants, darters and flamingos are able to co-exist in the same area due to their different dietary preferences and foraging techniques.

The outstretched wings of cormorants on the waters edge are a common sight. They spread their wings to dry their feathers, which a re not water repellent like the feathers of most water birds. the water logging of the feathers aid the cormorants in remaining under water for long periods whilst hunting for food.

Plants

Fluctuating temperatures, salt content, and oxygen have resulted in a variety of plants adapting to wetlands. Phytoplanktons are consumed by large quantities of fish. Sea grasses help bind the soil and provide suitable habitat for many invertebrate species. Reeds are mainly found where the salt content is lower. They filter silt and nutrients from water. Mangroves are the only trees adapted to these conditions. They grow aerial roots that stick out of the soil and absorb oxygen.

Fish

Species such as spotted grunter, white teenbras, leervis, mullet, and cape stumpnose are just a few of the species that are dependent on wetlands, and in particular estuaries for part of their life cycle. Most fish that occur in Estuaries breed in the sea. Their offspring return to the estuary and remain there for most of their life before they in turn must breed. Estuaries offer protection from most marine predators and the higher temperatures and abundant food supplies favour rapid growth of juveniles

Invertebrates

Invertebrates are plentiful and may be attached, free-swimming or burrowing . They feed on organic deposits, living plant tissue, particles obtained using filtering appendages and capturing living organisms. They are in turn, an important food source for certain fish, birds, reptiles and mammals. Bait species such as mud and sand prawns, pencil bait, bloodworms, mussels and polychaete worms are often overexploited.

Certain species of invertebrates are used as indicator species to determine the general health of rivers and streams.