Public outcry prompts Environmental Department to reconsider chemical solution for Vaal River alien species

Water lettuce, alien invasive species flooding the Vaal river. Picture: Timothy Bernard / Independent Newspapers.

Water lettuce, alien invasive species flooding the Vaal river. Picture: Timothy Bernard / Independent Newspapers.

Published Feb 18, 2024


The Department of Forestry, Fisheries and the Environment (DFFE) has back-tracked on its bid to use sub-lethal chemicals to rid the Vaal River of invasive alien species following a growing public outcry over the long-term effects on the river.

Since December 2023, the Vaal River has become overrun with water lettuce and some water hyacinth, an invasive aquatic species originating in South America, with negative environmental and socio-economic implications.

As a result, 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, including physical removal, bio-control and chemical application, as advised by experts by the Environmental Department.

Rand Water initiated the use of chemical glyphosate to clear the species, and avert further impact to the river or spreading of the species.

However, while some applauded the action taken to assist the community in ridding them of the alien species, some raised concerns shortly after the project began, of the long-term impact on the river’s water quality as a result of the chemical sprays being utilised.

It was highlighted how in 2015 the World Health Organization’s (WHO) International Agency for Research on Cancer (IARC) reclassified glyphosate as probably being carcinogenic to humans.

This was despite the IARC’s conclusion not being confirmed by European Union assessment or the recent joint assessment by the Food and Agriculture Organization of the United Nations.

South Africa Vaal Water lettuce 16 February 2023. In 2023, substantial floods in the Vaal area may have resulted in an unintentional discharge of water lettuce (pistia stratiotes) into the primary river, contaminating approximately 35 kilometres of it with this highly proliferative invasive aquatic weed. Rand Water suspects that the water lettuce may have initially been employed to absorb nutrients from a sewage spill into the Vaal River, but it has now spread to more extensive sections of the river. Currently, it is restrained at the barrage wall, and with only a few weeks remaining before the annual floods, there is limited time to prevent the weeds from advancing to the next 1000 kilometers of the Vaal River and subsequently into the Orange River. On Tuesday, herbicide was applied to the growth, and the Vaal River community is optimistic that the introduction of Weevils and Hoppers, insects known to feed on the lettuce, will prove beneficial. In recent months, water hyacinth affected the Hartebeespoort Dam and the lake in Benoni, and these insects were successful in addressing the issue. Areas such as Millionaires Bend in Sasolburg are currently entirely covered in a green carpet of water lettuce, raising concerns about its potential impact on marine life due to restricted sunlight penetration into the water. Picture: Timothy Bernard / Independent Newspapers.

In heeding the public’s concerns and complaints regarding the use of chemicals, the Water Department and the Environmental Department issued a joint statement. In this statement, both ministers agreed to assess whether the 'clearing' methods employed by the authorities align with the regulatory environment.

Peter Mbelengwa, head of the Environmental Department, said in addition, the ministers would also devise a future plan that would ensure that the clearing of the alien invasive plants was done in a manner that poses no harm to the environment.

Mbelengwa said once that process was concluded, the department would issue a further indication on the way forward.

According to researchers, invasive alien plants are a significant problem in South Africa as they have negative impacts on the environment by decreasing both surface water run-off and groundwater recharge, causing direct habitat destruction, intensifying flooding, and increasing the risk and intensity of wildfires.