Eight South African lakes with unique characteristics have been identified in the course of the National Biodiversity Assessment 2018. Experts emphasise the need to protect these wetlands from environmental and other pressures that threaten to degrade them.
Scientists have singled out eight South African lakes for their unique characteristics. “These are the only depressions or pans in South Africa – that we know of – which are more than two metres deep, making them unique,” says CSIR senior researcher, Dr Heidi van Deventer. She adds that a 100% biodiversity target has been set on these lakes. The biodiversity target is the minimum proportion of an ecosystem type that needs to be kept in a natural or near-natural state, in the long term, to maintain viable representative samples of all ecosystem types and the majority of species associated with those ecosystems.
Wetlands, in general, are impacted in several ways, including water abstraction, deteriorating water quality, invasive species, land degradation and fragmentation, climate change and a collapsing capacity of expertise to monitor and minimise the impacts. “This tends to change the condition and threat status of the ecosystems,” she says. “The 2018 National Biodiversity Assessment (NBA 2018), due to be released in 2019, will model the condition of wetlands on a national scale.”
The eight unique lakes were distinguished from other water bodies from a literature review, including CSIR reports, websites and journal papers, conducted for the NBA 2018, during which the first South African Inventory of Inland Aquatic Ecosystems was established. The inventory offers a collection of data layers pertaining to the aquatic ecosystem types and pressures for both rivers and inland wetlands. According to the inventory, South Africa boasts a total of 158 407 wetlands of which 147 044 are inland wetlands and the rest are rivers and estuaries.
The National Biodiversity Assessment
The NBA is a national collaborative effort led by the South African National Biodiversity Institute (SANBI). Van Deventer leads the inland aquatic component of the NBA 2018, which contains a rivers subcomponent led by CSIR senior researcher, Dr Lindie Smith-Adao. CSIR senior researcher, Dr Lara van Niekerk leads the estuarine component of the assessment. The assessment also contains a terrestrial and marine component, which is led by SANBI.
The assessment evaluates the state of South Africa’s ecosystems based on best available evidence and is used to understand trends over time and inform policy and decision-making across a range of sectors, including mining, fisheries and agriculture. It informs South Africa’s Outlook reports on the Sustainable Development Goals to the United Nations Environmental Programme and the Convention on Biological Diversity.
2018 NBA: Estuarine component
An estuary is a body of water containing freshwater from rivers and saltwater from the sea, forming a transitional zone between the river and maritime environments. The major pressures on estuaries include pollution, flow modification, overfishing, habitat modification and emerging pressures from alien species and desalination. “These pressures are increasing and it is challenging to track the condition every five years because aquatic systems do not change that fast,” says Van Niekerk. More than half of South Africa’s estuaries are in good health, but over 60% of estuarine areas have been modified significantly, placing a strain on important ecological functions, such as nursery functions and fisheries production.
2018 NBA: Rivers subcomponent
South Africa boasts a total of 200 955 km of rivers, measured in length. A key finding of the NBA 2018 points to only 33% of South African rivers being in good condition. Smith-Adao warns that the country’s rivers are impacted severely by flow alteration, resulting from damming or over-abstraction, habitat destruction, invasive alien plants and pollution of water. Hence, free-flowing rivers are rare features in our landscape. A free-flowing river is a long stretch of a relatively large river that has not been dammed or does not experience major flow alteration. The NBA 2011 identified 19 flagship free-flowing rivers which are an important part of our natural heritage. Examples include the Doring, Elands and Mtentu Rivers. These rivers should be protected to maintain their free-flowing character.
Eight unique lakes
The eight unique lakes cover just over 13 000 hectares. They are Barberspan, Chrissiesmeer, De Hoop, Groenvlei, Lake Banagher, Lake Fundzudzi, Lake Sibaya and Tevredenpan. Lake Sibaya is the largest freshwater lake, making up more than 8 000 hectares or 63% of all of the lakes. It provides freshwater to the communities surrounding it.
Source: CSIR
