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Climate change a threat to fynbos

Published May 17, 2012


Melanie Gosling

Environment Writer

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NEW research indicates that the drier winters caused by climate change could spell the end for the Cape’s unique fynbos.

UCT researcher Mike Meadows, from the department of environment and geographical science, one of the international team who did the research, said in a statement that future drier conditions and the increased risk of fire could put fynbos at risk of extinction.

“These plants are tough and they are already used to dry conditions, but further aridity could make fires more frequent, which could damage the soils and make it even harder for the native plants to survive here.

“Unfortunately, this is their only native habitat, so such a change here might eventually threaten their very existence,” Meadows said.

The team’s findings support what sophisticated climate models had been suggesting would happen in the Cape in the future.

With the build-up of greenhouse gases, global temperatures will rise. This in turn will have an effect on the westerly winds that bring the Cape its rainfall.

This band of westerly winds that circles the Antarctic shifts with the seasons: in the cooler months it moves north over the Cape, bringing winter rainfall and in the summer it moves south, where the rain falls over the ocean.

Many climate models suggest the global increase in temperatures will force these westerly winds to move towards the Antarctic during this century – a trend which has already been observed, meaning a drier Cape. Now the research Meadows and colleagues have done supports this prediction.

Meadows took sediment cores at Verlorenvlei near Eland’s Bay on the West Coast, and by examining diatoms, tiny single-cell algae in the cores, was able to reconstruct past rainfall patterns at the site going back 1 800 years.

They then looked at data from ice cores taken in the Antarctic, to test their assumption that the changes in rainfall at Verlorenvlei had been linked to ancient changes in the movement of the westerly winds towards the poles. They found that this was the case.

Guy Midgley, from the SA National Botanical Institute, said yesterday one of the strengths of the research was that it had increased the confidence of the climate model projections, which suggested that the Cape would become more arid.

“The Verlorenvlei cores extend the rainfall record back to 1 800 years. We’ve been keeping rainfall records for around only 100 years. One of the key things is if the westerlies move south, it switches off the winter rainfall. Not a 10 percent reduction, it’s just not there,” Midgley said.

The research should be seen as a warning, he said.

“This will not affect only fynbos, but water supplies, agriculture and people’s lives. It will be very difficult for Cape Town to adapt to those changes. But this is not set in stone: if the world is able to get greenhouse gas emissions under control, we can avoid that.”

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