World Ocean Census - Extract 26 - The path forward

14 September 2010

Some news stories of the past decade are shocking, almost unbelievable. They range from the “great Pacific garbage patch” – a flotilla of trash nearly the size of Africa that tends to trap and kill marine life – to reports of massive coral reef bleaching and destruction, to vast dead zones, void of oxygen, that can no longer support life. When you dig deeper, past the headlines, into what scientists have actually discovered, some of the stories become more convincing, and in some cases the news is truly ominous.

Scientists estimate, for example, that half of the coral reefs in the Caribbean and a quarter of the reefs around the world are now dead. It is believed that this devastation is mainly due to pollution, physical destruction and increasing ocean water temperatures, a direct result of global warming (most coral species can survive only in very narrow temperature ranges). Complicating their survival further is the rise in concentrations of atmospheric carbon dioxide (CO2). This is causing changes in the ocean’s carbonate chemistry system that will affect some of the most fundamental biological and geochemical processes of the sea. Since 1980, ocean uptake of excess CO2 released into Earth’s atmosphere by human activities is significant: about a third has been stored in the oceans. This uptake of CO2 lowers the ocean’s pH, making it more acidic, which in turn causes lower saturation states of the carbonate minerals used to form skeletal structures by many major groups of marine organisms, including corals. Scientists predict that if nothing is done to correct this condition, all of the remaining coral reefs could be dead by 2075.

Another disturbing story is about the large dead zone off the coast of Namibia. Scientists are measuring it as they watch it expand year after year. The only inhabitants that remain in this zone are jellyfish, often described as the cockroaches of the sea in recognition of their ability to thrive under adverse conditions. While larger than many, Namibia’s dead zone is not unique. A 2008 report in Science by Robert J. Diaz, from the Virginia Institute of Marine Science, and Rutger Rosenberg, of the University of Gothenburg in Sweden, suggests that there are now more than 400 dead zones around the world, double what the United Nations reported only two years earlier. Collectively, these dead zones affect a total area in the world’s ocean of more than 245,000 square kilometers (98,000 square miles).

Text and images reprinted with permission from World Ocean Census: A Global Survey of Marine Life by Darlene Trew Crist, Gail Scowcroft and James M. Harding Jr., Firefly Books, 2009.

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