A plan to drill into aquifers in the mountains near Cape Town, South Africa, to address the city’s water crisis could harm the region’s rich biodiversity, ecologists say.

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Ecologists up in arms over Cape Town’s plans to ease water crisis by drilling into aquifer

CAPE TOWN, SOUTH AFRICA—In the mountains east of here there are plants so rare they are only found in an area the size of a soccer field. Some could be extinct in a matter of months, ecologists warn, if city officials proceed with plans to drill into aquifers to help ease a looming water crisis.

Cape Town, South Africa’s second most populous city, is battling its worst drought in decades. Reservoir levels were retreating so sharply during summer in the Southern Hemisphere that officials had warned that the city’s water supply would be shut off on “Day Zero” in April, forcing most of the city’s 4 million inhabitants to queue for rationed potable water. Day Zero has since been put off to July, and if the winter rains come as usual, Cape Town may not have to turn off the taps this year.

Even if Cape Town dodges that bullet, water shortages are anticipated to continue. The city’s plans to source more water include desalinization plants due to come online later this year, wastewater recycling, and drilling into aquifers beneath the city and surrounding mountains. These aquifers already provide water for farmers and private individuals, but the municipality has not drilled into them on a grand scale—until now. 

Officials say that tapping aquifers under the Table Mountain group could provide 40 million liters of potable water per day—less than a tenth of the current, restricted demand. In November 2017, the city began sinking test boreholes in the mountains, and it plans to drill dozens more.

But ecologists warn that depleting the aquifers would threaten the unique biodiversity of the Cape Floral Region, a UNESCO World Heritage site. “You can literally wipe out a species by developing an area not bigger than a tennis court,” says Adam West, an ecologist at the University of Cape Town.

In an 8 February letter to local authorities, West and four colleagues argued that the drilling would mar the heritage site, and lowering the water table would harm dozens of wetland species. One sensitive area where test boreholes have been drilled is Wemmershoek Valley, the only known home of Erica bakeri, a shrublike plant with delicate pink flowers. Efforts to cultivate this plant elsewhere have failed, says Ismail Ebrahim, a botanist with the South African National Biodiversity Institute here. “There is nowhere for it to go,” he says. West says clearing thirsty alien vegetation such as pine and black wattle from dam catchment areas could save more water than the city plans to pump out of the aquifer.

Western Cape province is “aware of the concerns,” a spokesperson says, and authorities have “engaged with the relevant role players to find mechanisms to identify sites and methods that reduce the in situ impacts on the receiving environment.” But there is no indication that Cape Town authorities have revised the drilling plan, and they had not responded to a request for comment by the time ScienceInsider posted this story. “It seems like they are ducking and diving,” West says.