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Alien invasion is sucking SA’s water reserves to the bone


Alien invasion is sucking SA’s water reserves to the bone

Eradicate non-indigenous trees such as pine and there would be enough water for 3.38 million households

Senior reporter

The volume of water consumed by invasive trees annually is enough to sustain over three million SA households a year – nearly a quarter of all of the country’s homes.
Research, which involved the Council for Scientific and Industrial Research, the University of Cape Town and the World Wide Fund for Nature SA (WWF-SA), has revealed that 1.44 billion cubic metres of water are consumed annually by invasive vegetation.
The research reveals that should these plants – most of which are located on farms, river banks and water catchment areas – be eradicated, there would be enough water for 3.38 million households with an average of four inhabitants. The same volume is also enough to irrigate 120,000ha of agricultural fields annually.
According to the 2011 census there are 14.5 million households in SA.
Shelly Fuller, of WWF-SAs sustainable agriculture section, said the research showed the extensive dangers posed by alien plant species.
She said farmers had traditionally planted alien plants species, such as pine or beefwood, to act as windbreakers.
“Both, which are extremely thirsty trees, were introduced because they grow fast and straight and are perfect for windbreaks and plantation requirements.”
Fuller said while clearing invasive alien plants was very expensive, “landowners have recently begun connecting these costs as a type of ‘insurance’, both in terms of water security and fire risk management.
“On average, clearing one hectare of alien vegetation in a catchment area releases nearly 2,000 kilolitres annually.”
She said many farmers were now proactively removing the invasive alien plants from their farms.
“The recent runaway fires in the Overberg region [in the Western Cape] highlight how if each landowner, both private and state, manages their firebreaks and clears invasive alien tree species, it will make fires far less damaging both for business, society and the environment.”
She said climate change was speeding up the spread of invasive plants because of higher carbon dioxide levels and temperatures.
“If clearing of the invasive plant patches is not done properly ... the problem is exacerbated, which is the case in many areas of the country.”
Klaudia Schacthschneider, manager of WWF-SAs water stewardship programme, said roughly 6.5% of SA’s available fresh water was consumed by alien invasive plants.
“Compounding the country’s water provision problems is people’s mindset that we can simply get more water from dams or rivers. This is what has landed us in our water crisis.”
Schacthschneider said an excellent example of where people were realising the benefit of clearing alien invasive trees was in the Western Cape’s Upper Breede River area around Ceres, Slanghoek and Wolseley under the Upper Breede Collaborative Extension Group.
“It is a massive collective of different role players. Under this group there has been co-operation between different government departments and over 100 farmers, through NGOs, to cut back alien vegetation from a river in the area. They have cleared over 75km of river banks, freeing up vital water reserves. They then conduct yearly maintenance plans to stop invasive tree seedlings from sprouting again.”
Ceres pear and apple farmer Steven Versfeld said while a hugely expensive process, the benefits, which are not always immediate, would be immense in the future.
“I have seen how areas of fynbos can be completely dwarfed by pine trees, with one tree suddenly morphing into 60 and growing not only in the mountains, but in the rivers which get sucked dry.”
He said doing nothing would be disastrous.
“If I don’t act this vegetation risks sucking up to at least 30% of my water reserves. We owe the future generations to leave it in good condition.”
Henko Vlok, Sustainable Initiative of SA’s environmental specialist, said alien invasive trees grew faster than indigenous plants, “using up to 40% more water than local plants”.
“From a food security perspective such vegetation poses a severe risk to the country. It is clear from the research that to ensure food security we need to improve the country’s water availability. To do that invasive plant species must be removed.”

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