Wetlands

 A basic guide to understanding wetlands

What is a wetland?

The word wetland usually conjures images of areas with tall reeds, open water and lush green vegetation. Although this image is true for the typical floodplain type wetland, this is just one of a variety of wetland types.

The term “wetland” is a generic term for all the different kinds of habitats where the land is wet for some period of time each year, but not necessarily permanently wet. Water which falls as rain or snow in the catchment, and which is not lost to the atmosphere through evaporation or transpiration, moves through the catchment to the sea. Wetlands are found where the landform (topography) or geology slows down or obstructs the movement of water through the catchment (e.g. where the landform is very flat), or where groundwater surfaces causing the surface soil layers in the area to be temporarily, seasonally or permanently wet. This provides an environment where particular plants (hydrophytes) that are adapted to wet conditions tend to grow in abundance. The plants in turn affect the soil and hydrology (e.g. by further slowing down the movement of water and by producing organic matter that may accumulate in the soil).

Many wetlands therefore occur in areas where surface water collects and/or where underground water (also referred to as groundwater or subsurface water) discharges to the surface (commonly referred to as seeps, springs or fountains), making the area wet for extended periods of time. Other wetlands occur along our coasts, such as estuaries and sometimes even coral reefs.

The term wetland therefore refers to aquatic systems that can be permanently saturated, as well as areas that occur at the other extreme, i.e. areas that are rarely saturated. Because wetlands occur between these extremes, they are often viewed as “transitional” ecosystems that share characteristics of both the wetland and non-wetland habitats.

Why are they important?

Wetlands provide significant economic, social and cultural benefits. They are important for primary products such as pastures, timber and fish and support recreational and tourist activities. Wetlands also help reduce the impacts from storm damage and flooding, maintain good water quality in rivers, recharge groundwater, store carbon, help stabilise climatic conditions and control pests. They are also important sites for biodiversity.

Wetlands are important ecologically, because they moderate water flow and regulate water quality. They act as sponges during wet periods, therefore controlling the extent and impacts of flooding and droughts. They slow down the flow of water, causing suspended matter to settle out or to be absorbed by wetland plants. Wetland plants are specifically adapted to flourish in areas of higher than average concentrations of certain elements.

Wetlands are among the most threatened aquatic habitats in South Africa, and it is estimated that up to 50% of wetlands may have been lost country-wide. Threats to wetlands include human activities, such as channelisation, drainage, crop production, effluent disposal and water abstraction. Loss of wetlands leads to a reduction or loss in biodiversity, as the plants and animals that are adapted to wetland habitats are often unable to adapt to new environmental conditions, or to move to more suitable ones. Loss of harvestable resources also occurs when wetlands are lost. For example reeds and grasses are important materials in traditional construction, and reduction in these resources creates a dependence on other materials such as wood, plastics, and metals, which have negative environmental impacts. Loss of water quality and flow regulation is a further consequence of loss of wetlands, and may result in greater extent or severity of flooding.

Of the more than 800 naturally-occurring freshwater wetlands in South Africa, 14% have full protection within a national park, provincial nature reserve or wildlife sanctuary and 4% are partly protected. South Africa currently has 16 wetlands designated as wetlands of international importance in accordance with the Ramsar Convention.