The lake behind the Hartbeespoort Dam in South Africa used to be brimming with people enjoying scenic landscapes and recreational water sports. Now, the visitors are greeted to the sight of boats stuck in a sea of invasive green water hyacinth weed.
The spike in Harties — as Hartbeespoort is known — can be attributed to pollution, with sewage, industrial chemicals, heavy metals and litter flowing on rivers from Johannesburg and Pretoria.
“In South Africa, we are faced with highly polluted waters,” said Julie Coetzee, a professor who has studied water hyacinths for more than 20 years and manages the aquatic weeds program at the Centre for Biological Control at Rhodes University in Makhanda.
Nutrients in the pollutants act as perfect fertilizers for the weed, a big concern for nearby communities due to its devastating effect on livelihoods.
Dion Mostert, 53, is on the verge of laying off 25 workers at his recreational boat company after his business came to a standstill because of the carpet of water hyacinths.
“The boats aren’t going anywhere. It’s affecting tourism in our town ... tourist jobs,” said Mostert, pointing toward his luxury cruise boat Alba marooned in the weeds.
He has considered using herbicides, but said it would only be a quick fix against the weed.
However, scientists and community members have found a unique way to deal with the invasion by introducing a water hyacinth-eating bug called Megamelus scutellaris.
The tiny phloem-feeding insects are the natural enemy to the plants. Both are originally from the Amazon basin in South America.
The insects destroy the weed by attacking tissue that transports nutrients produced in the leaves during photosynthesis to the rest of the plant.
The insect army has previously reduced the expanse of water hyacinths to a mere 5 percent in the dam-created lake, Coetzee said.
At times the weed has covered at least 50 percent of it.
Environmentalist Patrick Ganda, 41, mass rears the bugs at the Grootvaly Blesbokspruit wetland conservancy southeast of Harties, once home to more than a hundred species of birds that attracted a lot of tourists.
However, unable to find food such as fish and small plants with much of the wetland’s water covered in plants, there are only two to three species of birds left, he said.
Scientists warn that while the insects have been fairly successful in controlling the situation, more needs to be done to treat its cause, which authorities could tackle by tightening regulations on wastewater management.
“We are only treating the symptom of a much larger problem,” said Kelby English, a scientist at Rhodes University.
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