Data sets show climate change trends

Fifty years of comprehensive data sets on the Benguela Current Large Marine Ecosystem are now providing marine scientists with a good picture of how climate change is being felt - both at sea and on land - in the subcontinent.

A list of 11 trends, watch points for environmentalists and scientists, emerged from a recent climate change workshop that was organised by the Benguela Current Large Marine Ecosystem (BCLME) Programme under Professor Vere Shannon of the Department of Oceanography, and attended by UCT researchers in allied fields.

The BCLME stretches from just east of Port Elizabeth up the west coast of South Africa and Namibia to Cabinda, the northern-most province of Angola. It's a complex and variable ecosystem that has a profound affect on climate in southern Africa.

Long-term trends include frequent warm events off northern Namibia and southern Angola, declining and shifting fish stocks, changing sea temperatures (which affect rainfall and weather conditions), and increased southerly winds. These winds induce upwelling in the Benguela, with consequences for the region's fisheries.

One of the most obvious trends is ocean warming at the southern and northern boundaries of the BCLME, with possible repercussions for fish stocks and terrestrial climate.

Changes in the BCLME have hit the fishing industry hard. Pelagic stocks (sardine and anchovy) in the northern Benguela have succumbed to heavy fishing pressure, leading to the almost total disappearance of sardine shoals off Namibia. In the southern Benguela, sardine stocks have shifted eastwards, away from the traditional fishing grounds on the west coast.

Horse mackerel stocks off southern Angola and Namibia have declined.

There is no evidence of changes in hake distribution in the southern Benguela. But in Namibia, deepwater hake appears to have expanded northwards.

Rock lobsters have declined in the central Benguela and moved southwards and eastwards in the southern region.

The scientists say it's not clear whether all these changes can be linked exclusively to climate change or whether they're part of inherent, natural long-term cycles.

"Future research and monitoring efforts will need to focus on a much broader approach in space and time," a report said.

This means improving collaboration between the region's oceanographic and atmospheric institutions and the development of a strong global perspective.