More bad news about the oceans

Posted by Laura Grant on February 23, 2008
Posted in Green News

Fishery hotspots from

The millions of people who rely on fishing to make a living could be in for a hard time thanks to climate change because scientists expect it to have a serious impact on the oceans’ already dwindling fish stocks.

A UN Environment Programme report released this week, entitled In Deep Water, maps the impact of pollution, overharvesting and alien infestation on the world’s fisheries and then adds climate change to the mix – and the findings make depressing reading.

The worst-affected 10 to 15 percent of the oceans are also home to the world’s most important fishing grounds, the report found. And up to 80 per cent of the world’s primary fish catch species are already exploited beyond or close to their harvesting capacity.

Dead zones, areas of de-oxygenated water caused by pollution, have increased from 150 in 2003 to 200, the report says. Alien invasive species, which can out-compete and dislodge native ones, are increasingly associated with the polluted, overharvested and damaged fishing grounds, it adds. And the concentration of “alien” species matches the major shipping routes.

Add to this climate change and the situation is even bleaker. For instance, if the ocean’s thermohaline circulation were to slow down at least 75 percent of the world’s major fishing grounds would suffer further. Half the world’s fish catch is caught along continental shelves in an area of less than 7.5 percent of the globe’s seas and oceans, the report says. This “natural pump” circulates nutrients in the ocean and “flushes and cleans” wastes and pollution from the continental shelves.

“Imagine what will happen if climate change slows down or stops these natural food transport and “flushing” effects in waters that are often already polluted, heavily fished, damaged and stressed”, said Dr Christian Nellemann, who headed up the rapid response team that compiled the report. “We are gambling with our food supply”.

Higher sea surface temperatures threaten to bleach and kill up to 80 percent of the world’s coral reefs – which are nurseries for fish.

Plus there are growing concerns that carbon dioxide emissions will increase the acidity of seas and oceans, reducing the availability of calcium carbonate which shell-forming marine life, including corals, use to form their shells. It will also have an effect on the tiny planktonic species that form the bottom of the food chain, the report says.

“We are getting more and more alarming signals of dramatic changes in the oceans. It is like turning a big tanker around. Our ability to change course and reduce emissions in the near future will be paramount to success”, said Dr Nelleman.

Stefan Hain of UNEP’s World Conservation Monitoring Centre, said it was critical that existing stresses were also addressed in order to conserve fish stocks and coral reefs.

This is the second report this month containing depressing news on state of the oceans.


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