Tue, Oct 19, 2021 page6

• Cape Town fights alien tree species that threaten its water supply, biodiversity

  • Reuters, CAPE TOWN
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  In South Africa’s Franschhoek mountains a helicopter drops off abseilers to cut down invasive pine trees that are choking off water supplies to millions of Cape Town residents already facing climate change-induced shortages.

  The crews are there to help to remove 54,000 hectares of alien trees by 2025, in the process reclaiming an estimated 55 billion liters of water lost each year — two months of water supply for Cape Town.

  Using hand saws to cut saplings while dangling over craggy cliffs, the team is targeting infestations of alien tree species, mainly pine, but also Australian acacia and eucalyptus, that carpet swathes of mountainside in dark green foliage.

  

  An invasive pine sapling sits amongst indigenous vegetation above Caledon near Cape Town, South Africa, on Tuesday last week.

  Photo: Reuters

  “We can’t eradicate the pines, but we’ve got to manage and control them because the scale is too big. It’s a massive problem,” said Louise Stafford, South Africa’s program director at The Nature Conservancy, a non-governmental organization leading the process.

  The control of the pines was fast-tracked in 2018, when Cape Town narrowly avoided having its taps run dry during a drought dubbed “Day Zero.”

  Pine trees, first introduced from Europe during the 17th century, are now the backbone of South Africa’s commercial forestry industry. However, their small seeds are easily dispersed by the wind and, with no natural enemies, they can spread rapidly from plantations to protected nature reserves, scientists said.

  The alien trees also threaten native animals and plants in the Cape Floral Kingdom, where 70 percent of the plants, like the famous fynbos range of plants that are found nowhere else on the planet.

  A single pine tree consumes at least 20 percent more water than the fynbos.

  The animals under threat include the rough moss frog, which was discovered in 2008, about 100km east of Cape Town on the slopes of Caledon’s Klein Swartberg mountains, which are drained by three vital rivers.

  “Out of the five sites we are monitoring, three no longer have any [rough moss] frogs. If we do not remove this carpet of pine trees there is no doubt the frogs will become extinct,” said John Measey, a zoologist at Stellenbosch University’s Centre for Invasion Biology.

  Removing dense pine thickets is a huge task, but necessary.

  “We are eating this elephant piece by piece,” Klein Swartberg Nature Conservancy chairman Lambert Fick said, as workers prepared ahead of a controlled fire to clear the area — a practice that some conservationists regard as risky.

  Introducing moths, weevils or mites is also being considered to combat the trees, said Andrew Turner, a restoration ecologist at government agency CapeNature.

  “It is not a silver bullet ... [they] cannot get rid of existing infestations, but rather stop it spreading further,” he said.
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