The City’s fight against alien vegetation could yield big results for water security

In the delicate surrounding Cape Town, a battle against invasive tree species is unfolding, driven by the urgent need to secure the city’s water supply. The Greater Cape Town Water Fund, comprising government, businesses, and conservation groups, is leading this charge, recognizing that invasive species like black wattle, pine, and gum trees are exacerbating water scarcity by consuming excessive groundwater and hindering water flow into reservoirs.

The City of Cape Town and The Nature Conservancy are also clearing invasive pine and eucalyptus trees from key water catchment areas like Wemmershoek, Steenbras, Berg River, and Theewaterskloof.

This initiative, launched in July 2021 with a R50-million budget, aims to clear 11,617 hectares over two years and has already created 1,088 jobs. The project targets invasive species that contribute to significant water losses, estimated at 55 billion litres annually, according to a 2018 study by the Greater Cape Town Water Fund.

Initial control operations cost up to R40,000 per hectare, with ongoing costs decreasing as plant density decreases. However, experts like Jasper Slingsby warn that the current investment is insufficient, estimating that R370-million is needed for catchment restoration to yield 50 billion litres of water annually.

Removing invasive species is crucial, as these plants currently drain billions of litres of water and pose a greater threat to Cape Town’s delicate native ecosystem. of the 20,400 species of plants found in the Cape, more than 2/3rds are found nowhere else in the world. Several of our native species have already been driven to extinction by invaders, and a further 14% are under threat.

The decision to remove these invasive species stems from scientific findings that eliminating them can yield significant water gains. Projections by hydrologists suggest that removing foreign tree species could provide Cape Town with an additional two months’ worth of water, a more cost-effective solution compared to alternatives like desalination.

Efforts to clear invasive trees have been substantial, with crews using chainsaws and controlled burns to clear 120 square miles over three years, with more to come. Recent data from the Nature Conservancy, a key partner in the project, highlights the impact of this work, showing that areas with native fynbos vegetation exhibit 34% higher water flow than those invaded by pine trees.

The initiative’s success is underscored by independent research, which found that clearing mature infestations of alien trees can increase available water by 15 to 30 percent. While such methods have been used in countries like the United States, Canada, and Australia, Cape Town’s unique circumstances, including the invasive species’ water-intensive nature, justify their removal.

The conservation efforts face challenges, including the impact of invasive species on local biodiversity. Invasive plants have already driven several native species to extinction, threatening the delicate balance of the local ecosystem. However, the initiative has received widespread support from various stakeholders, highlighting its importance in both environmental and economic terms.

Former firefighter Ayabonga Velem now leads a team of workers in clearing invasive species, demonstrating the initiative’s positive impact on local employment and community development. The project not only addresses environmental concerns but also provides economic opportunities for those involved.

As Cape Town continues to grapple with water scarcity, the conservation efforts to remove invasive species play a crucial role in restoring natural ecosystems and ensuring sustainable water resources for the future.

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