Wetlands provide important ecosystem services

Wetlands are considered one of the richest in terms of services provided.

Palmiet wetlands provide important ecosystem services to society but are in such a critical state that if we don’t act now, they may soon disappear right before our very eyes.

“It’s been reported that over 65% of South Africa’s wetlands and associated river systems have been damaged and 50% estimated to have been destroyed. If steps are not taken immediately to restore Palmiet wetlands threatened with erosion, it is possible that these wetlands will be drained or lost by 2065,” says Dr Alanna Rebelo, a wetland ecologist and postdoctoral researcher in the Department of Conservation Ecology and Entomology at Stellenbosch University (SU).

Dr Rebelo recently obtained her doctorate in Conservation Ecology at SU.

Her research focused on the Theewaterskloof and Goukou wetlands in the Western Cape as well as the Kromme wetland in the Eastern Cape. Located in the Cape Floristic Region, one of the world’s biodiversity hotspots, these wetlands have a remarkably similar vegetation composition.

Two of these Palmiet wetlands are situated upstream of large municipal reservoirs that provide water for Cape Town and Port Elizabeth.

Dr Rebelo measured their soil and water chemistry, vegetation community structure and groundwater parameters to try to understand what they are like in terms of their biochemistry, and in particular what physical aspects drive the vegetation community structure.

She used a combination of aerial photograph analysis, remote-sensing and modelling techniques to map the current and historical distribution of wetlands and what remains of them, how their spatial distribution has changed over time and what the main drivers of this change are. She also wanted to determine how wetlands function in providing ecosystem services.

Dr Rebelo says that of all ecosystems, wetlands are considered one of the richest in terms of services provided.

“They attenuate floods, mitigate water pollution, retain sediment, provide clean water and food for local communities, and capture and store atmospheric carbon dioxide. They also have valuable peat-beds beneath them which, if degraded, will contribute to global warming.”

Dr Rebelo says despite this, the complexity of wetland ecology has resulted in them being the least studied. She mentions that South Africa’s wetlands are not well understood and many are in decline.

“The ecosystem services the Palmiet wetlands provide could soon come to a halt,” she says.

“The remaining wetlands are threatened by a plethora of different problems such as being removed to make place for agriculture, gully or channel erosion, pollution from agricultural runoff like lime and fertilisers, invasion by alien vegetation, increasingly extreme flooding and inappropriate fire regimes.

“Bisecting roads also have a negatively impact on Palmiet wetlands because they cause knick-points in wetland systems, often resulting in erosion, which eventually drains the wetland.”

“Once this erosion begins, it is impossible for the system to recover without active rehabilitation, which is costly.

“This wetland drainage results in a shift in vegetation communities.”

Dr Rebelo points out that the value of Palmiet wetlands in terms of water purification, amongother ecosystem services, has been overlooked in favour of their potential for fertile soil for food provision.

“As a result, many of these Palmiet wetlands have been ploughed up for agriculture, either for orchards or grazing.”

She says it’s unfortunate that landowners often believe that Palmiet chokes rivers and that it should be removed.

“It is in ‘choking’ rivers that Palmiet is able to provide many important ecosystem services to landowners, and to others further downstream.

“These include slowing the force of dangerous floods thereby minimizing infrastructural damage, allowing deposition of sediment which then would not accumulate in the dam, and in dispersing the movement of water, in doing so providing a filtration service and improving water quality.”

Dr Rebelo says her findings highlight not only the uniqueness and value of Palmiet wetlands, but also their decline and make a case for their conservation and restoration.

“It is hoped that the findings of my study will feed into conservation and restoration planning, and possibly policy, with real implications for the protection of ecosystems and biodiversity.”

“The protection and restoration of our wetlands should be a national priority,” concludes Dr Rebelo.