Debates have raged for decades over the best way to “save” Lake St Lucia, a vast and complex estuary system whose ecological health is shaped by the joint influence of fresh water and salt water.
The 70km-long lake, home to a rich variety of animals, birds and water life, is the centrepiece of the iSimangaliso Wetland Park, South Africa’s first World Heritage Site and second-largest protected area after Kruger National Park.
It is also the largest estuarine lake system in Africa, serving a vital and nationally important role as a nursery ground for sea fish, prawns and other marine creatures.
Depending on the year, the season and other factors, the shallow waters of Lake St Lucia can be completely fresh on one hand, or many times saltier than seawater.
This time-series of aerial images clearly shows the extreme fluctuations
of water levels in the lake during and after a drought period. (Images: iSimangaliso Wetland Park Authority)
Yet, despite its size and protected status, the lake and its abundant wildlife have been in trouble for decades, sparking heated debates over what should be done to protect them.
Now, more than a decade after a multimillion-rand rehabilitation project to reconnect the lake to its single biggest lifeline of fresh water (the Mfolozi River) – and a decision to ensure “minimum human interference” in natural processes – a group of four local estuarine researchers has stirred up fresh controversy by calling for the resumption of regular, human-driven breaching of the St Lucia estuary mouth, dredging and other management interventions.
The changing shape of the Mfolozi River mouth between 1883 and 1966. (Map: Whitfield and Taylor 2009) Bulldozers and sugar cane: The degradation of Lake St Lucia Before getting into the details of the latest proposals, it may be useful to go back in time to get a better understanding of how we got here. The year 1952 was a pivotal moment in the recent ecological history of Lake St Lucia. This was the year that bulldozers and other machinery were deployed to sever the lake’s single-largest water artery – the Mfolozi River, which historically provided at least 50% of the lake’s freshwater inflows.
For hundreds, possibly thousands of years, the Mfolozi River emptied into the Indian Ocean at the same spot (near the present-day St Lucia village). Apart from flowing into the ocean, the Mfolozi waters also flowed sideways into the lake when the mouth closed off in dry periods.
But by 1952, park managers feared that the Mfolozi was now carrying too much silt into the mouth of the lake and – perhaps more importantly – neighbouring sugar cane farms were also pressing for action to protect their farms from being flooded when the river mouth closed up.
The first commercial sugar farms were planted here in 1911, smack inside the Mflozi River floodplain. The wet, fertile soils were great for growing sugar, but from an ecological perspective, the decision to reroute the mouth of the river turned out to be a disaster.
Before the arrival of the farmers, this floodplain was the place where the river slowed down before meeting the sea, dumping large volumes of sediment before its waters entered Lake St Lucia.
During the 1930s, farmers also began to alter the ecology of the floodplain by changing the natural course of the Mfoloizi, installing drains, canals and levies to protect their low-lying plantations from back-flooding during storms or periods when the mouth closed naturally.
Fairly soon, the lake’s ecological pendulum began to shift. Combined with canalisation, drainage and alterations to the position of the river mouth, Lake St Lucia was robbed of its largest water supply.
With less water in the lake, another ripple effect was that the St Lucia estuary mouth became increasingly clogged with sediments from both the sea and land, prompting a massive dredging operation in the mid 1950s.
According to former Ezemvelo KZN Wildlife ecologist Dr Ricky Taylor, it took nearly five years of dredging before the link between St Lucia and the sea was opened, and another eight years of dredging to remove all the accumulated sediment.
Eventually, however, when the lake almost dried up during another dry cycle in the early 2000s, estuarine experts made a decision to reconnect the Mfolozi River mouth to where it had always been.
The farmers fought back, demanding the right to breach the mouth artificially. But they lost their battle in the high court and a subsequent appeal to the Supreme Court.
In her ruling in 2017, high court Judge Mohini Moodley said that the farmer’s insistence on breaching the river mouth was self-serving and outdated, and reflected a conscious lack of concern around the environmental degradation .
Large sections of the Mfolozi floodplain — once a trap for muddy sediments — have been turned into sugar cane plantations. (Photo: Tony Carnie) Most of Lake St Lucia dried up almost completely in 2016 due to the lack of fresh water, killing off fish and other aquatic…
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