Port Alfred is renowned for its wetlands. These have been the subject of many a controversial discussion for so many years. In tourism, we constantly beg the "powers-that-be" to think before they stamp, to understand the dire consequences of making decisions for people yet to take their place amongst us.

Our estuaries are dwindling. They are not being cared for. With the upsurge of tourism, more and more people are buying anything that will race them over the waters. Little thought is given to the river banks, the life under the water or the effects that these motorised modes of pleasure will have on the waters. Just out of town, the largest of our wetlands are being suffocated under the garbage that people throw away, supposedly from gardens. In town, the area known as The Duck Pond is likely to be developed. With a fair amount of thought, it is up to us, the concerned, to ensure that the careless people who throw litter, the builders who have no thought of preservation and the buildings that will try to sneak their waste into the environment, will be monitored.

Estuaries are the meeting places of the rivers and the sea, and are characterised by the interaction between the two. Conditions in an estuary are always changing, and this instability or variability is one of the most important features of estuaries. The salinity of estuarine water varies depending on the tide and the strength of the inflowing river. In addition, a river also brings silt and nutrients to the estuary in varying quantities, depending on conditions in the catchments area (drainage basin) of the river concerned.

Why are estuaries important?
Conditions in estuaries are very different from those in the sea. Estuaries are usually calm, sheltered and shallow, and vary greatly in temperature, salinity and turbidity (murkiness). As a result they are specialised environments.

A nursery for marine species: More than 100 species of fish, prawns and crabs in South African off-shore waters use estuaries as nurseries and/or feeding grounds. The life cycle of most of these species involves egg production at sea; often close inshore and near an estuary mouth. Eggs and larvae develop at sea, but the larvae and juveniles migrate to estuaries in great numbers. In fish, this migration takes place mainly during late winter, spring and early summer when millions of juveniles swim into estuaries.

Estuaries are good nurseries because they offer protection from most marine predators, and their high temperatures and rich food supplies favour rapid growth of the juveniles. The source of this food supply is estuarine plants growing in the water, as well as the plants of the neighbouring wetlands such as mangroves and reeds. These plants supply most of the detritus (fragmented remains of dead plants and animals) which, together with bacteria responsible for decomposing detritus, forms the basis of the estuarine food web.

Most juvenile fish migrate back to sea at an age of about one year. These sub-adults tend to live close to the shore, where they join adult spawning populations once they become mature.

Estuaries and people
Estuaries are favourite sites for human settlement, urban development and recreation boating, fishing etc. Many cities and towns along the coast depend on estuaries for harbour facilities, tourism and recreation, e.g. Durban, Richards Bay and Knysna. They are particularly popular with anglers when adult fish enter seasonally to feed. At these times fish are easier to catch and are important as a source of both food and recreation. An example of this is the famous Spotted Grunter "run" into KwaZulu Natal and Cape estuaries. Of the 81 fish species which depend on estuaries in South Africa, 29 are sport angling species and an additional 21 species are used for human food.

Threats to estuaries
Anything that happens to a river in its catchments area can have an impact on the estuary. A river flowing through farmlands can become polluted by pesticides, herbicides and nutrients from fertiliser. Soil eroded from badly farmed or overgrazed lands will also be washed into estuaries after heavy rains. This excessive silt load has the effect of filling up the estuary and in some cases resulting in the estuary mouth closing. Silt smothers animals and reduces light penetration so that plants are unable to grow except in very shallow water. Damming of rivers and the use of water for irrigation or industry can lead to freshwater starvation of an estuary. This upsets the ratio of freshwater to sea water in the estuary which in turn affects the plants and animals living there.

What you can do
Get to know the estuaries in your area by walking along their shoreline or canoeing throughout their length. Report signs of damage to the local authority. List the plants and animals living in these estuaries. Photograph the upper, middle and lower reaches of the estuary from fixed vantage points and monitor change between seasons and from year to year. Find out what the estuary is used for, which local authority is responsible for its management and what strategies have been prepared to control development alongside it.

Did you know?
Bad catchments management is the major cause of estuarine damage in southern Africa. The numbers of many important commercial (e.g. prawns) and angling species (e.g. cob, grunter, perch) which rely upon estuaries are dwindling as a result of disturbed estuarine environments.