“Alien invasive species take over the natural functioning of ecosystems,” said Department of Forestry, Fisheries and Environment (DFFE) Minister Barbara Creecy from Heidelberg, Gauteng last Friday, during the launch of the new R2.6-billion project, which forms part of the Working for Water Programme.

“It is for this reason our Department is happy today to announce this five-year programme to combat alien species and the damage they do to our land, wetlands and rivers.”

This programme aims to control invasive alien plants over 1.2-million hectares across all nine provinces over five years and create 38,839 work opportunities every year, primarily in rural communities throughout the country. 

Minister @BarbaraCreecy_ assisting with clearing #alien #invasive plants and stacking them to prevent soil erosion. pic.twitter.com/qEzWiwTZjS

— Environmentza (@environmentza) November 17, 2023

This project is part of the Working for Water Programme, first launched in 1995, that focuses on removing invasive alien plants and bush encroachments from critical waterways and wetlands. 

According to the South African National Biodiversity Institute’s (Sanbi) latest status report on Biological Invasions and Their Management from 2019, invasive trees use 3-5% of South Africa’s runoff water every year, and many species of invasive plants are also less drought-resistant than indigenous ones. 

“Invasive alien species are brought in from other parts of the world, and where they come from, originally, they have got a whole lot of pests and diseases and things, predators that keep them in check.” Dr Brian van Wilgen, ecologist and Emeritus Professor of the Centre for Invasion Biology at Stellenbosch University explained to Daily Maverick.

“When you bring them here, all of those checks are gone — that’s why they become so aggressively invasive.”

The department explained that ​​invasives threaten biodiversity, water security and quality as well as destroy the productive use of land and ecological functioning of natural systems. 

Van Wilgen, who was the first Scientific Advisor to the Working for Water programme (between 1996 and 2004) explained that even though R2.6-billion sounds like a lot, there are over 200 alien invasives plants and species that need to be controlled in the country – but we’re only getting  to less than 1%  of that per year, while we estimate that  the problem is spreading at between 7.4 and 15.6% annually.

In terms of water security, van Wilgen explained that “many of these plants, especially invasive trees, use much more water than the vegetation that they replace. In a water-scarce country like South Africa, you start running into problems”.

The plants also pose an additional threat of fuelling wildfires and increasing soil erosion if left unmanaged.

For example, van Wilgen explained that pine trees in the Cape, that have outcompeted the indigenous fynbos, can grow to 10 metres high (whereas fynbos is only one metre.)

“There’s so much more fuel to burn when a fire comes along, that the fires are very, very difficult to control, they’re much more damaging.”

Pine trees can grow up to 10 metres high, much higher than the indigenous fynbos that they’re outcompeting in the Cape – creating more fuel for fire. (Photo: PHYS.ORG / Wikipedia)

Biodiversity as a buffer against climate change

During the launch of this programme, the DFFE emphasised that invasive species interfere in natural processes that can help mitigate the effects of natural disasters through the provision of ecosystem services and that invasive species exacerbate floods, droughts and wildfires, and have negative impacts for the forestry and agriculture sectors.

“In short, biological invasions will exacerbate the effects of climate change and the extreme weather events associated with global warming,” said Minister Creecy. 

“By clearing waterways and managing the spread of invasive species we are restoring natural habitats and simultaneously restoring ecosystem services that will assist us in the fight against the effects of climate change.”

For years the scientific community has been highlighting how climate and biodiversity issues are interlinked — not only do depleted ecosystems contribute to climate change, and vice versa, but strong ecosystems can be used to enhance our resilience to anthropogenic climate change.

“If you keep your ecosystems intact, whether there are climate extremes… the ecosystems will be able to cushion us from the impact of climate change,” said Shonisani Munzhedzi, CEO of Sanbi.

An example, Munzhedzi said, is how functional wetlands and functional strategic water sources can absorb extreme rainfall, an impact of climate change that will only increase in frequency and intensity in a high-carbon future. 

“If it rains hard for 20 days, the water gets to be mitigated — absorbed into the wetland system, the wetland system will deal with it.”

Read more about the climate-biodiversity link in Daily Maverick: Marine Protected Areas are our insurance policy for a climate-uncertain future

Van Wilgen explained that invaded ecosystems don’t have the same water-holding capacity as the natural vegetation does, so if there’s good natural ground cover in catchment areas, it’s less likely to have flash runoff from that catchment area, for example.

But van Wilgen emphasised that while “alien species disrupt the normal functioning of natural ecosystems which protect us from a lot of things. they don’t act by themselves — they just exacerbate the problem that’s caused by other things as well,” — such as building dams, and pollution. 

Business as usual won’t solve the problem

“South Africa is one of the few countries that has a programme like this that is tackling this problem,” said van Wilgen about the Working for Water programme.

“And so it is to be praised. But it needs to improve its efficiency and its planning.”

Van Wilgen, who was the first Scientific Advisor to the Working for Water programme (between 1996 and 2004) explained that even though R2.6-billion sounds like a lot, there are over 200 alien invasives plants and species that need to be controlled in the country — but we’re only get to about 4% of that per year, and the problem is spreading at 6% annually.

For example, van Wilgen explained that black wattles, brought in from Australia, “have invaded enormous areas, where they use a lot of water, and they displace important grazing for livestock.”

#WorkingForWater Programme participants are busy clearing blue gum, red river gum and black wattle, which are #alien #invasive plants in Heidelberg. pic.twitter.com/La0XLfKqr3

— Environmentza (@environmentza) November 17, 2023

A 2016 study van Wilgen co-authored found that to successfully achieve the control of a maintenance level will either require funding to be substantially increased or if control were to focus on fewer selected areas.

Van Wilgen explained that, “most ‘business as usual’ scenarios will result in the problem running away from us.”

And instead, van Wilgen’s study suggests that management can be improved by practising conservation triage, “focusing effort only on priority areas and species, and accepting trade-offs between conserving biodiversity and reducing invasions”.

Conservation ‘triage’

Van Wilgen explained that the term “triage” comes from the Napoleonic Wars, when thousands of wounded soldiers flooded hospitals, and doctors had to divide patients into those that needed immediate treatment, those that were beyond help, and those that did not need immediate treatment.

“And we’re getting to the position now, where we have to make those kinds of decisions with our ecosystems,” explained van Wilgen. “We might not be able to save all of the protected areas in the country, but there’s quite a few that we can save if we concentrate the money in those areas and use it more effectively.”

Between 1998 and 2020, R7.1-billion (adjusted to 2020 values of ZAR) was spent by Working for Water’s projects on interventions to control alien plant invasions, according to a 2022 study van Wilgen co-authored that looks at what the Working for Water programme has achieved over 20 years.

Control efforts were directed at 178 species covering 2.7 million hectares, which is 14% of the estimated invaded area (over two decades). The study noted that over a quarter of the control was not in priority areas for biodiversity and/or water conservation. 

The study found that while there has been a reduction of alien plants at a local scale, national surveys suggest that plant invasions have continued to grow: “The problem is too large to expect that control can be achieved everywhere”.

Thus, the researchers recommended that they should instead practise, “conservation triage, focussing on clearly defined priority sites, improving planning and monitoring, and increasing operational efficiency.”

For this R2.6-billion five-year project launched last week, there are projects spread through all nine provinces in SA, and our national parks.

“You get a lot of small projects springing up all over the place, because then they can say, look, we’ve created jobs in every province,” said van Wilgen. “But then in that way, you dilute the funds to a point where they are ineffective.”

Creecy said at the launch, “I think that one of the important innovations that our department has done with this new working for water programme is that we have contracted with small enterprises in rural areas for a five-year period to clear a specific area.”

Creecy said that in the past they had very short-term contracts, and found that the alien invasives simply returned. 

Van Wilgen acknowledged that the department has done some prioritisation exercises, but the National Treasury requires them to maximise the number of jobs. 

“The projects that come in with the lowest cost per person per day, get preference,” said van Wilgen. “In other words, they employ more people because they spend less on other things like herbicides or management research — which upsets the prioritisation exercise even more. “

Along with conservation triage, van Wilgen’s research has suggested that more funding would be needed to control the species in perpetuity (as complete eradication is impossible in most instances).

The 2022 study found, based on several estimates, that the cost of clearing existing invasions in South Africa would require three to seven times more money than what has been spent to date. 

Biological control agents

Another suggestion would be to ramp up biological control agents. Van Wilgen explained that this is when insects or pathogens control the growth of the species.

“If you were really serious about the problem, I would spend 10 – 30 times more on biological control than you are because it holds so much promise,” said van Wilgen, “the problem is it doesn’t immediately create a lot of jobs”.

Van Wilgen explained several examples of where biological control agents brought a species under complete control is not a problem anymore.

The biggest success story was bringing prickly pear cacti under control in the 1930s. Van Wilgen explained that prickly pear cactus infestations had driven farmers off their land, and the biological control was so successful that within a couple of years, they were able to return. 

In Kruger Park, insects were able to bring substantial contribution to the control of a type of cactus (Opuntia stricta) in residual infestations of the weeds that have been treated with herbicides.

Another example is with the water hyacinth at Hartbeespoort, where it was found that under the right circumstances, very good control can be achieved with “inundative release strategies” — i.e. releasing large numbers of insects at once. DM