Scientists digging into the past in a cave outside Cape Town may have found the key to understanding the future.
A study of cave stalagmites, some more than half a million years old, suggests the Cape’s world-famous flora diversity is linked to its stable climate. Plants do better in areas where they don’t need to adapt to changing weather, the findings suggest.
However, the authors say the “diary” of climate information contained in the stalagmites also holds a dire warning: the more unstable a climate, the less likely a species is to survive, underlining the impact of man-made climate change being felt worldwide.
Chemicals “frozen” in the stalagmites reveal clues about the water and air of the ancient Cape landscape. By comparing their results with stalagmite samples from other sites worldwide, the research team confirmed a long-held theory — that the Cape’s extraordinary floral diversity coincides with an extraordinarily stable climate.
“The more stable, the richer the flora, with the Cape at the head of the pack,” said South African botanist Richard Cowling, of Nelson Mandela University, part of the research team that has been sampling caves for years.
The team also included world-renowned scientist Prof Curtis Marean, whose work at the sites at Pinnacle Point in the Southern Cave helped establish South Africa as an archaeological “hotspot” and lead contender as the original “cradle of human culture”.
Marean told TimesLIVE Premium the latest cave study provides further evidence that humankind was just one of multiple species that benefited from the Cape’s relatively stable climate. “It shows the region is one of the most stable climates through time worldwide,” he said.
But the results also “provide a dire warning of the downstream impacts of rapid climate change that we are now experiencing. Our study shows that rapid climate change annihilates plant lineages, so the human-induced rapid climate change we see today will do the same, with horrific consequences for the animals and humans that rely on those plants.”
Ironically, the stalagmites, having survived several ice ages, were undone by human activity, though scientists managed to at least sample them before the site was disturbed by mining.
“The cave was discovered by members of the Cape Peninsula Speleological Society in an active limestone quarry and extraction operations were planned to destroy the cave,” the authors said in the study, published recently in the Journal of Biogeography. The cave was known simply as CLC1.
Five stalagmites were subsequently taken from it using hammers, chisels and saws. They were then cut in half and “mined” for their chemical information. Sample dating was done in Israel and the US. Collectively, the samples covered the period from 243,000 to 676,000 years ago, with a few gaps in the timeline.
Sample analysis showed climate variations were lower at the Robertson cave site compared with other northern hemisphere sites during the same time period. More samples are needed to compare Robertson samples with those from other South African caves during the same period.
The link between the Cape’s rich floral biodiversity and its relatively stable climate, though exceptional, is likely one example of a broader global correlation between biodiversity and climate, the study concludes: “Indeed, it may well be true that the Cape is not an exception and that climate stability is part of a more general explanation for plant diversity patterns.”
Oresti Ventouras, a Cape speleologist who runs a caving conservation company Mystical Caves, said caves contain huge biodiversity and are a window to the past.
“What life was there on this planet way before humans arrived? As archaeologists and researchers are discovering more and more about life on Earth in caves, it is proof enough to say that caves are a very important and crucial part of our existence, and they need to be protected and conserved,” Ventouras said.
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