E Cape environmentalists combat invasive water plants

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Climate change has led to water scarcity in many parts of South Africa and the problem is worsened by alien invasive water plants damaging water bodies and ecosystems.

However, environmentalists in the Eastern Cape are employing innovative strategies to address the issue. At the Waainek Mass Rearing Facility in Makhanda, scientists breed insects known as biological control agents to manage invasive water weeds, particularly species native to South America that have proliferated in South African rivers.

These water weeds, such as water hyacinth and water lettuce, obstruct water flow, harm biodiversity, and pose health risks to animals and humans.

According to scientist Samella Ngxande-Koza, these plants block sunlight, water and air from reaching other organisms, leading to their demise.

Ngxande-Koza says, “All the other biodiversity under the plant, doesn’t get water, doesn’t get the sun, doesn’t get the air so they suffer and end up dying because these plants cover the entire surface, no sun coming in whatsoever.”

They keep the cochineal insects on plants in quarantine to assess their effectiveness.

Ngxande-Koza says, “So, the plant that we have here is called the yellow flag iris or Iris pseudacorus from Europe. We started with the trial, host-specific trial since 2018 and it takes a very long time ‘cos we want to make sure that we run through the tests thoroughly. We don’t take short cuts ‘cos at the end of the day that might come back and bite us.”

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Research is also underway to address concerns about water quality when the invasive plants die.

Masters student Rochelle Bessing states how they are developing methods to treat the nutrient-rich water left behind.

Bessing says, “There were some people that were concerned that it’s now creating a jelly layer on the floor of the water body and that it’s gonna make huge nutrient increases in the water. So, water hyacinths love nutrific water that’s loaded with nutrients, so that’s not great for us. When this water hyacinth finds this nutrient-rich water i.e bad quality water that’s when it thrives so water hyacinths is just a symptom of bad water, so that’s what we are trying to treat.”

Though the research is not yet complete, Bessing says no eminent threats have been detected.

“So, when it does die, we’ve removed the symptom and people are worrying that we are making a whole other new concern for the nutrients in the water and so far, we haven’t found that it has a huge effect. It just kind of releases all the nutrients back in that it took up so it’s pretty a circle of life kind of a thing,” explains Bessing.

Researchers, farmers, and concerned individuals interested in preserving biodiversity are encouraged to seek assistance from the Centre for Biological Control if they encounter invasive plants on land or in water.

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