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Cape Town fights alien trees threatening its water supply, biodiversity

In South Africa’s Franschhoek mountains, crews have started cutting down invasive pine trees that are choking off water supplies.

The commercial timber plantations at Newlands are of invasive alien pine trees. These spread their seeds en masse into the surrounding indigenous vegetation. Newlands Forest. Cape Town. Source - S Molteno, Public Domain.
The commercial timber plantations at Newlands are of invasive alien pine trees. These spread their seeds en masse into the surrounding indigenous vegetation. Newlands Forest. Cape Town. Source - S Molteno, Public Domain.

In South Africa’s Franschhoek mountains, crews have started cutting down invasive pine trees that are choking off water supplies to millions of Cape Town residents already facing climate change-induced shortages.

While cutting down trees – any kind of trees – may seem counter-productive during the climate crisis, removing 54,000 hectares (133, 437 acres) of alien trees by 2025 will result in reclaiming an estimated 55 billion liters of water lost each year – equivalent to two months water supply for Cape Town, according to Reuters.

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 the mountainside in dark green foliage.

“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, an NGO leading the process.

Species Pinus pinaster Family Pinaceae. Author – unknown, CC SA 3.0.

Are pine trees native to South Africa?

The simple answer is a big NO, pine trees are not an indigenous feature of South Africa’s environment. The seeds for various types of pine trees were first bought over in the 17th century, (1685–1693) at the behest of the First governor at the Cape, Jan van Riebeeck. His cargo included the maritime pine, Scots pine, Norway spruce, oak, and ash tree seeds.

The maritime pine, Pinus pinaster, ended up spreading to the Cape Peninsula by 1772. Towards the end of the 18th century (1780), P. pinaster was widely planted, and at the beginning of the 19th century (1825–1830), P. pinaster was planted commercially as a timber resource.

It should be noted that this particular pine tree is widely planted for timber in its native area, being one of the most important trees in forestry in France, Spain, and Portugal. It has also been cultivated in Australia as a plantation tree, to provide softwood timber.

Over the past 350 years, the maritime pine has become the backbone of South Africa’s commercial forestry industry. But 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.

: A portion of Theewaterskloof dam, close to empty in 2018, showing tree stumps and sand usually submerged by the water of the dam. Source – Zaian, CC SA 4.0.

Now, water, and biodiversity are under threat

Cape Town’s current water crisis date back to the extreme drought from 2015–2017. Things got so bad that by mid-January 2018, former Cape Town Mayor Patricia de Lille announced that the City would be forced to shut off most of the municipal water supply if conditions did not change.

The control of the pines was fast-tracked in January 2018 when Cape Town narrowly avoided having its taps run dry during a drought dubbed “Day Zero” designated as April 12, 2018. Of course, at that time, disaster was averted only because people cut their water usage to a drastic level. It didn’t have anything to do with the trees, yet.

In one study dating back to 1982, it was found that P. pinaster has the potential to dramatically alter the quantity of water in the environment. If P. pinaster invades an area covered with grasses and shrubs, the water level of the streams in this area would lower significantly because P. pinaster takes up considerably more water than grasses and shrubs all year round.

This propensity to take up water also results in the depletion of water in catchment areas and reduced flow in rivers. This depletes the resources available for other species in the environment, including the famous fynbos range of plants that are indigenous to South Africa.

https://commons.wikimedia.org/wiki/File:Peninsula_Sandstone_Fynbos_-_Cape_Town_8.JPG
Peninsula Sandstone Fynbos. Unique vegetation type endemic to the Cape Peninsula. Cape Town. South Africa. Source – S Molteno, Public Domain

 In the Mpumalanga Province, 6 streams completely dried up 12 years after grasslands were replaced with pines. After areas of dense P. pinaster were thinned and the number of trees in the area decreased, stream flows resumed.

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,” John Measey, a zoologist at Stellenbosch University’s Centre for Invasion Biology, said.

So, removing dense pine thickets is a huge task, but necessary. “We are eating this elephant piece by piece,” Lambert Fick, chairman of the Klein Swartberg Nature Conservancy, said, as workers prepared ahead of a controlled fire to clear the area – a practice that some conservationists regard as risky.

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We are deeply saddened to announce the passing of our dear friend Karen Graham, who served as Editor-at-Large at Digital Journal. She was 78 years old. Karen's view of what is happening in our world was colored by her love of history and how the past influences events taking place today. Her belief in humankind's part in the care of the planet and our environment has led her to focus on the need for action in dealing with climate change. It was said by Geoffrey C. Ward, "Journalism is merely history's first draft." Everyone who writes about what is happening today is indeed, writing a small part of our history.

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