From left: The polyphagous shotworm beetle (Photo: S Bush / FABI) | The polyphagous shotworm beetle. (Photo: S Bush / FABI) | The autumn army worm. (Photo: SANBI)
South Africa spends over 1 billion rupees each year fighting an army of alien invaders – but there is a never-ending task ahead of us to limit the relentless spread of a multitude of foreign organisms that rich the country’s water resources, farmland and wealth biological heritage.
Some of the stowaways arrive on our shores desperately on the underwater floors of ships and recreational yachts from the Caribbean or the Caribbean Mediterranean Sea-. Others hitchhike in the belly of huge cargo ships, in the cargo holds of passenger planes, trucks or trains.
Many others too are welcomed with open arms because of their bright colors, strange shapes, and other novel properties.
However, since most enter the country without passports or papers – or are simply too small to be seen by the human eye – it is impossible to count how many intruders arrive in South Africa each year.
The hulls of pleasure yachts, encrusted with a host of alien and local marine organisms, are just one of the many routes that extraterrestrial invaders can use to creep into South Africa. (Photo: Tammy Robbinson)
Still, a new assessment by local scientists has officially classified nearly 2,000 alien species that have built a fairly solid bridgehead on our coasts and are expanding to take advantage of a vast hinterland where they have no natural enemies to limit their invasion.
The most noticeable alien invader was SARS-CoV-2, the tiny virus behind the Covid-19 pandemic that killed well over 55,000 South Africans in the past year.
But there are many other, less visible and less vilified intruders … tiny beetles, mushrooms, or herbivorous armyworms. Songbirds like the Indian Mynah; commercial pine and mudflat trees, or brightly colored lizards imported by animal traders, or foreign cold-water fish species such as trout known as “finned chainsaws”.
A notable intruder is the polyphagic shotworm (PSHB) (and its symbiotic fungus) from Southeast Asia, which is eating its way north after being discovered in Pietermaritzburg in 2017. Since then he has been in all provinces except Limpopo and. spread has killed thousands of trees, including several historical specimens around George and Stellenbosch.
At the release of the latest scientific assessment of South Africa’s biological invasions on Friday, National Environment Minister Barbara Creecy said PSHB is expected to become one of the most harmful and costly biological invasions in the country.
Creecy said biological invasions are now the third largest threat to South Africa’s biodiversity after cultivation and land degradation, accounting for 25% of all biodiversity loss.
Recent estimates have shown that the land could lose up to 70% of this valuable natural resource if biological invasions on grazing land were not controlled.
The last report from the SA National Biodiversity Institute (SANBI) provides a comprehensive assessment of the status of invaders and is the only country-level assessment worldwide that specifically focuses on biological invasions.
South Africa occupies only 2% of the world’s land area, yet is home to 10% of the world’s plant species and 7% of reptile, bird and mammal species – many of which are displaced or threatened by invasive alien species.
This historic oak, planted in the city of George in 1884, is one of the victims of the alien polyphagous shotbore beetle. (Photo: Eugene Gunning, George Herald)
Given that South Africa is already spending more than Rs.1 billion annually to control such invasions, Creecy announced that her department recently received a significant cash injection from the Global Environment Facility.
The funding consists of approximately R46 million in grants and an additional R303 million in benefits in kind to strengthen management of invasive alien species.
Some are being used to tackle eight prioritized species of intruders and implement new surveillance and detection measures at border posts. Some are also used to eradicate the alien house mice that kill the chicks of rare seabird species on Marion Island in the Southern Ocean.
There are more than 70 official ports of entry through which people, goods and transport ships can enter the country. Eight are seaports, 10 are airports and 54 are land border posts.
Currently, however, there are only adequate biosecurity control measures in place at OR Tambo International Airport, while the other ports have very limited or sporadic biosecurity capacities.
According to the latest scientific findings, at least 1,880 alien species have now established themselves in South Africa, around a third of which have been classified as invasive.
Examples are plant pests such as the tomato leaf miner discovered in 2016 and the autumn army worm in 2017.
The autumn army worm from North and South America feeds on the leaves and stems of more than 80 plant species and causes great damage to corn, rice, sorghum and sugar cane, but also to other vegetables and cotton.
It’s called the “army worm” for good reason. In its larval stage, it gathers in huge masses that can destroy large areas of cultivation overnight, while moths of this species can fly up to 100 km per night.
Dr. Tsungai Zengeya, managing editor of the SANBI report, said the environmental cost of invasive alien plants and animals is estimated to be more than R6.5 billion a year.
The main costs are associated with a decline in ecosystem services such as water and pasture, as well as agriculture.
Scientists estimate that invasive trees consume up to 3-5% of South Africa’s surface water every year, a serious problem in an already arid country that is increasingly prone to drought.
While that number may not seem high, SANBI scientists said that day zero in Cape Town has been brought forward by 60 days because invasive trees in the area are sucking up water. Similar effects exist in other drought-affected areas such as the Eastern Cape.
The report also highlights another significant threat posed by invasive trees. As they provide additional wood fuel, they increase the risk and intensity of steppe fires such as those recently struck Knysna.
SANBI researcher Dr. Katelyn Faulkner found that at least three new invader taxa enter the country every year, including foreign marine organisms that enter South African waters through ballast water that comes from thousands of kilometers away.
Some organisms also attach to the hulls of ships and pleasure boats, and recent research in local waters has highlighted the role of recreational yachts, particularly those used for cruising, in the spread of marine alien taxa in South Africa.
More than 100 alien plant species have invaded South African national parks and game reserves. Most were deliberately brought into the country as ornamental plants or dispersed by rivers and animals.
Examples are a freshwater snail (Tarebia granifera) from Southeast Asia, which spreads rapidly in the country via aquatic plants and birds or as a stowaway on boats and trailers.
The report emphasizes the need for adequate funding and management to combat invasion of alien plants with consistency and determination.
One example of this is a severe setback in weed control in the 90,000 hectare Hluhluwe-iMfolozi Park in KwaZulu-Natal. The extraterrestrial triffid weed (Chromolaena odorata) was first discovered in the reserve in 1978 and then spread rampantly to cover more than half of the park by 2003.
After significant investments in weed control (R103 million in funding and 2,000 person-years of effort), invasions were reduced to an acceptably low level by 2011.
The success of this operation was now in question, however, as most of the profits have now been reversed “due to a number of aggravating factors,” the report said.
One of the reasons was the tragic death of a field worker who was killed by an elephant. This led to an instruction from the Ministry of Labor that teams were only allowed to work in the field when accompanied by an armed guard.
However, due to funding cuts in the province of Ezemvelo KZN Wildlife Agency, no additional armed guards were available and it was not possible to train and adequately remunerate new armed guards as part of the expanded public work programs. Since the implementing agency did not spend the funds allocated to the project either, the funds were withdrawn in accordance with the rules of the Ministry of Finance.
Although alternative sources of funding were later found, this resulted in a two year weed control halt on the reserve – during which Chromolaena reoccupied most of the cleared areas.
“Overall, the (initial) gains seem to have reversed, and additional funds would be required, which are unlikely to materialize in the current economic conditions, to bring the situation back under control. This experience illustrates the complexity of measures to control alien species, the need for more flexible approaches to deal with them, and the fact that invasions can quickly attack again if maintenance management is not implemented consistently and continuously. “
Creecy has also stressed the need for a more coordinated approach to solving the complex problem.
Recognizing that this was a multi-faceted problem that required a multi-faceted approach, Creecy said it was necessary to break red tape and the silos of different government departments in order to arrive at a common national approach.
Accordingly, her department developed a new guideline on the management of biological invasions, which is supported by a 10-year national strategy and an action plan for invasive species.
The aim of the strategy was to enable a more coherent and collaborative approach by government, industry and the wider community to identify and manage biosecurity risks. The new strategy will be published shortly for public comment and submission. DM