Invasive Alien Plant/Bird/Animal Infestations

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ALIEN INVASION

Spraying of controversial herbicide on Vaal River water lettuce begins – critics urge caution


The Taaibosspruit (a tributary stream connected to the Vaal River) is inundated with alien invasive species, with water lettuce covering the stream for kilometres. (Photo: Julia Evans)

By Julia Evans | 15 Feb 2024

As the invasive water lettuce continues to multiply along the Vaal River, Rand Water has begun an integrated response to halt the growth, spraying herbicide on the plants and releasing weevils as biological control agents. While the response is seen by some as necessary to urgently address socioeconomic implications, it’s seen as controversial by others.
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‘Under ideal conditions, it is safer and smarter to just implement biological control,” said Dr Leslie Hoy, the environmental management services manager for Rand Water.

“But you have a huge mat [of water lettuce], and that mat is impacting on people’s livelihoods, impacting on tourism, and impacting on people who rely on fishing on the Vaal Barrage. So you need to deal with it.”


Water lettuce blankets the water body, forming a ‘mat’ of just leaves, blocking out sunlight and preventing photosynthesis, greatly reducing oxygen levels, which can result in fish die-off. (Photo: Julia Evans)


Dr Leslie Hoy, environmental management services manager at Rand Water. (Photo: Julia Evans)

Hoy was speaking to Daily Maverick on the banks of the Vaal River in Vanderbijlpark on Thursday, 15 February. It has become overrun with water lettuce and some water hyacinth – invasive aquatic species that have environmental and socioeconomic implications.

• Why are invasives a problem?
  
  Water lettuce forms dense mats that clog waterways making boating, fishing, and other water activities, impossible. These mats also degrade water quality by blocking the air-water interface and greatly reducing oxygen levels, which can result in fish die-off and the overall reduction of aquatic fauna and flora diversity.
  Source: Julie Coetzee

Water lettuce exploded along the Vaal River in December 2023, causing residents to urgently find a solution to deal with the ever-growing plants.

Rand Water was given an urgent general authorisation by the Department of Water and Sanitation (DWS) to begin an integrated approach to manage the water lettuce, which includes physical removal, biocontrol and chemical application, as advised by experts by the Department of Forestry, Fisheries and Environment (DFFE).


To deal with the ever-growing invasive species water lettuce in the Vaal River, Rand Water has embarked on an integrated approach that includes physical removal, biocontrol and chemical application. (Photo: Sourced)

Glyphosate-containing herbicide was sprayed on the invasive water lettuce in sections of the Vaal River on 13 February in a sub-lethal dose. Rand Water said specific formulations of the glyphosate that were recommended are made based on DFFE expert opinion and research and this work is being monitored for compliance.

This has caused some controversy with many people concerned that using glyphosate-based herbicides – which is the most heavily applied herbicide in the world – would affect human health and drinking water.

“People are only looking at a section of the puzzle by not looking at the entire [problem] to understand the enormous impact,” said resident Thomas De Toit.

“The thing is we’re in crisis mode, and if it was left for decisions, and the volume doubled every two weeks. Time was absolutely against the community.”

Darryl Zaayman from The View on Vaal Resort said the water lettuce had a huge impact on tourism.

“We normally accommodate between 45 to 50 fishermen daily, they come and visit our facility. That number has literally dropped to four or five. So the financial impact of this has been massive,” Zaayman said during a stakeholder meeting with Rand Water at Stonehaven on the Vaal on Thursday.

“An integrated approach is the best way to deal with an invasion,” said Dr Julie Coetzee, a biological control scientist launching the biocontrol programme. “And the fastest way to knock these plants down is with a herbicide.”

Hoy said that the sub-lethal dose they used means the water lettuce won’t be killed outright: “You will kill them slowly and you’re knocking them back.”

Hoy explained that the whole growth system of the plant is impacted “and in that slowing down, you are giving other mechanisms a chance to come into play such as the biocontrol, and where possible physical removal.

“We just felt that this was really extreme and that we wanted to get it under a more manageable mass.”

Hoy added in earnest, “I understand concerns about glyphosate, and I really hope people are not freaked out by it… We’re trying to do the right thing.”

Concerns around glyphosate

Bettina Genthe, an independent consultant, previously at CSIR, has 40 years of experience in environmental health related to water quality. Genthe told Daily Maverick that she was concerned to hear they were using glyphosate because recent studies had shown that this widely used chemical herbicide could contaminate drinking water sources and air, could cause neurological diseases, and had been categorised by the World Health Organization as a probable human carcinogen.

However, Genthe said, “the dose is everything,” and that if Rand Water was using glyphosate only as an interim measure, and not routinely spraying the chemical, the exposure length would be less harmful. If the dose was repeatedly sprayed, it resulted in a higher dose in total, “because there would be adverse health effects in higher doses and on a prolonged basis”.

Hoy said that “to our knowledge, and because it was approved by DFFE, I am working on the basis that it will not negatively impact the water health,” and this is because they have taken all the precautions they are advised to.

Rand Water is using a specific formulation and non-lethal dosage rates they are required to comply with, and Hoy said that this low dose would be dilated by the large water body of the Vaal River and that the spray was targeted at the plants, which were grouped in targeted areas by the local community, not at the water body.

Hoy said there might be a need to spray again, but it was hard to pre-empt at this stage.

The area that is currently being affected by the water lettuce is below the abstraction points for Rand Water (Rand Water extracts from Vaal Dam). However, downstream of the spraying is a supply source for a major crop irrigation project (the Vaal-Harts government irrigation scheme).

Dr Ferrial Adam, executive director of citizen science organisation WaterCAN, said “while glyphosate may not have been sprayed in close proximity to Rand Water’s extraction areas, concerns arise regarding downstream water users’ potential impact”.

However, Hoy said this was not of concern because the dosage rate they complied with ensured it did not end up in drinking water.

“Rand Water has not done anything that goes against the law… We really want to do the best thing that we can,” said Hoy.


From left: Dr Julie Coetzee from the Centre for Biological Control, Dr Leslie Hoy from Rand Water and Mbuyiswa Makhubela from Rand Water during a meeting on 15 February 2024 with media and stakeholders about Rand Water’s approach to halting the spread of the water lettuce in the Vaal River, Vanderbijlpark. (Photo: Julia Evans)

Dr Samuel Motitsoe, an aquatic ecologist based at Wits University, said, “I think we should, by all means, stay away from chemical control/spraying in any dose because this is simply a quick fix and never sustainable.

“Let’s not look for quick solutions but rather make informed decisions that will not have long-term ecological impacts on our aquatic systems, the same way Racheal Carson’s Silent Spring warned us.”

Motitsoe added, “There is growing evidence that the chemical does affect aquatic microbes in the water column and on the sediments which are crucial on important ecosystem structure, functions and processes on aquatic systems. Thus the application of glyphosate in aquatic systems should not be taken lightly, more so that its fate is still under question.”

Professor Anthony Turton, a water resource management specialist at the University of Free State, holds similar views, stating that he is opposed to the use of glyphosate and that its use is irresponsible.

Turton said that along with glyphosate having an international reputation for being extremely controversial, he noted that the Water Research Commission’s 2023 study on glyphosate levels in SA cautioned that there were human health impacts that were as yet not fully understood.

“The report suggests that there is a very strong possibility of intergenerational impacts from the DNA-altering characteristics of this chemical,” said Turnton.

“So my response is very simple – the Precautionary Principle must prevail… If there is any question about the long-term human health impact of glyphosate, until such time as we know for certain what that is, we are obliged to err on the side of caution, and not use glyphosate.”

“The challenge lies in the potential development of immunity in water lettuce over prolonged exposure,” said Adam. “This immunity buildup can render the spraying less effective, and although the initial dosage may not be lethal, it can escalate into a significant problem over time.”

Adam also advocated against continued spraying of glyphosate, which has been banned in many countries around the world, and for bioremediation efforts.

Weevils (biocontrol)

“Water lettuce biocontrol is one of the best biocontrol programmes against invasive weeds in the world, but we need to ask people to be patient,” said Coetzee, the Deputy Director of the Centre for Biological Control (CBC), which once had a contract with the DFFE to implement biocontrol in SA.

• What is biocontrol?
  
  
  
  Biological control, in this case using water lettuce weevils, can lower the growth rate, reduce the size of the plants, and get into every nook and cranny where the plants are. Weevils feed on and tunnel into the leaves of invasive species, causing them to become waterlogged and sink.
  Source: Julie Coetzee

Ecologist Motitsoe agreed, saying “I would advise that we dive straight to biocontrol… the weevil is effective in controlling the weed and we should just invest in mass rearing the weevil and releases. Our research has shown promising aquatic system recovery (ecologically) following biocontrol of aquatic weeds and this is a bonus looking at it from a conservation lens.”


Weevils, small insects, are being used as a biological control agent to feed on and tunnel into the leaves of water lettuce causing them to become waterlogged and sink. (Photo: Julia Evans)


The Centre for Biological Control at Rhodes University has a rearing station for weevils (small insects on the water lettuce), and can mail these biological control agents to other parts of the country where they can be reared and used on invasive species. (Photo: Julia Evans)

And Hoy from Rand Water agreed that in an ideal world, just biocontrol would be used to deal with the invasives – but it is a layered issue, influenced by socioeconomic and time constraints.

Coetzee said that while she didn’t “necessarily think that this chemical spray is a good thing”, she was glad Rand Water had an integrated plan that included biocontrol and was prioritising it as the long-term solution.

On Thursday, Coetzee released the first biological control agents (weevils) outside Stonehaven on Vaal, to signal the start of the project, where weevils (reared at the CBC’s rearing centre at Rhodes University) will be released into specific areas that are reserved for biological control – where there’s no chemical spraying or mechanical removal – to create “biocontrol reserves”.


Dr Julie Coetzee, the deputy director at the Centre for Biological Control releases the first weevils (biological control agents), that feed on water lettuce, into the Vaal River on 15 February 2024. (Photo: Julia Evans)

“We don’t know what glyphosate does to the weevils, it’s never been tested,” said Coetzee. “So we don’t know if there’ll be direct mortality effects or if it will be indirect through plants dying.”

Rand Water is planning on entering into a memorandum of understanding with the CBC and has already set up a “hot house” in Alberton, where weevils can be reared.

The plan is for the CBC to supply the initial weevils and for Rand Water and residents to set up rearing stations and grow weevils so that when they have sufficient numbers, they can release more.

While debates swarm between which is the best solution to deal with these invasive species, as Turnton previously told Daily Maverick, this is like treating a symptom while ignoring the underlying illness.

The underlying cause of this issue is that the water in the Vaal River is eutrophicated — it has high levels of nutrients caused by sewage, agricultural run-off and industrial waste flowing into the river, creating an ideal environment for invasives to spread.

“Without addressing the sewage pollution flowing into the Vaal River, the cycle of water lettuce growth in the Vaal River could persist for decades,” said Adams. “Hartbeespoort serves as a grim example of what happens when such pollution goes unchecked, leading to severe compromise in water quality. We cannot afford to let other dams and rivers suffer the same fate.”

Another concern is that when the water lettuce is removed it will allow in sunlight, enabling the proliferation of cyanobacteria, which has toxins that can cause respiratory illnesses.

“My prediction is, in the next 24 months, we’re going to see an explosion, an exponential growth of blue-green algae in the Vaal River,” said Turton. DM

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Collapse all round.

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The easy way out

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Why South Africa spends billions fighting alien invaders


From left: Alien pine trees, which use substantially more water than the native vegetation of the Cape mountains, reduce river flows to dams that supply the city’s water. (Photo: Martin Kleynhans / The Conversation) | Sandfish are migratory freshwater fish found only in South Africa. As one of the largest grazers in South Africa’s Doring River system, sandfish keep the rivers clean and the food web balanced. (Photo: Jeremy Shelton) | Parthenium weed. (Photo: Invasive species South Africa / Wikipedia)

By Onke Ngcuka | 10 Mar 2024

Fighting alien invasive species cost the government R1.5bn between 2020-2022, with R10bn spent since 1995, which led to the creation of 825,000 jobs and the clearing of 3.6 million hectares of alien species.
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Alien invasive species in South Africa are competing with indigenous species for natural resources, disrupting ecosystems with ramifications for livelihoods, said Minister of Forestry, Fisheries and the Environment Barbara Creecy

Creecy was addressing the launch of the third South African National Botanical Institute’s (Sanbi’s) National Status of Biological Invasions and their Management report at Pretoria’s National Botanical Gardens on Friday. The report tracks alien invasive species data from 2019 to 2022.

Dr Theressa Frantz, Sanbi’s chief director of biodiversity research, assessment and monitoring, said 36 species were assessed, of which 19 — mainly trees and fishes — were found to have negative impacts at a national level. These species include pine trees, prosopis trees, parthenium weed and freshwater fish.

“In mountain catchments, alien species [were] cleared towards [Cape Town’s] Day Zero as they use a lot of water as they compete with people and biodiversity for scarce water resources. They also increase the intensity of fires and crowd out our indigenous biodiversity.

“Alien freshwater fishes are invading and reducing the diversity of our native fish and other organisms. While we have been doing well on risk analysis, much more needs to be done for appropriate management strategies to protect biodiversity and maintain ecosystem services that are essential to human wellbeing,” Frantz said.

Data gaps

The Sanbi report comes a year after the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (Ipbes) released a report which found that more than 37,000 alien species had been introduced to regions and biomes across the globe, with more than 3,500 of these being harmful. A previous Ipbes report found alien invasive species were one of the direct drivers of biodiversity loss.

“The Ipbes assessment revealed data gaps in South Africa, which is worrying. And this results in the underestimation of the impact of biological invasions. In 2019, the global annual economic cost of alien invasions was estimated to be $423-billion, which is of course an underestimation,” Frantz said.

An average of three new alien species per year had been accidentally or illegally introduced to South Africa between 2013 and 2022, Creecy said, adding that this was lower than the 2010-2019 average of four species per year.

The most harmful was an alien species of house mouse introduced to Marion Island which threatens the island’s seabirds.

Read more in Daily Maverick: Massacre at Marion: Mouse eradication project gathers pace

Creecy said tackling invasive species cost the government R1.5-billion between 2020-2022. She said R10-billion had been spent on this since 1995, which led to the creation of 825,000 jobs and the clearing of 3.6 million hectares of alien species.

Accidental or deliberate

Dr Katelyn Faulkner, co-author of the Sanbi report, told Daily Maverick that an alien invasive species introduced to South Africa about three years ago was of particular concern because of its potentially negative impacts on native trees.

“Seiridium neocupressi (a fungus), causes the disease cypress canker. This fungus was first recorded in South Africa in 2021 on the native tree Widdringtonia nodiflora (mountain cypress). Three species of Widdringtonia occur in South Africa.


Environment Minister Barbara Creecy with Working on Fire Programme participants eradicating alien invasive plants. (Photo: DFFE)

“The other species, W. wallichii (Clanwilliam cypress) and W. schwartzii (Baviaanskloof cedar), are endemic to South Africa and only occur in small populations that are already threatened. Before its introduction to South Africa, the fungus was only known to occur in Australia, New Zealand and Italy. We do not know with certainty how the fungus was brought into the country, but it was most likely brought in along with imported plants,” Faulkner said.

The report found that alien species were most prevalent in Western Cape, Eastern Cape and KwaZulu-Natal. Provinces with the greatest increase in alien plants were Western Cape, Gauteng and Limpopo.

Creecy told Daily Maverick that alien invasives were most prevalent in areas where they can be accidentally or deliberately introduced.

“Accidentally, it happens with visitors travelling, bringing with them organisms on their clothing. We know that we also find organisms in food that is imported.

“We have started nurseries in all [national botanical gardens] to sell indigenous plants. We try to attract the public to enjoy the garden, but also give them an opportunity to buy indigenous plants and plant them in their garden instead of planting exotic species,” the minister said. DM