Thursday, May 19, 2011

Coasts, oceans and greenhouse gases

An interesting piece has appeared in today's Nature magazine about the state of play of conservation issues in Brazil, namely coastal areas such as mangroves and sea grasses. Brazil contains 80% of the remaining Amazon forest and has been the focus of efforts to protect them but at the same time commercialise them. I won't go into arguments about the commercialisation of such rainforests except to say that Brazilians won't settle for a lower level of living compared to the rest of the developed world - which raises issues about our standard of living and whether it is sustainable.

But as the article states, while much emphasis has been placed on rainforest, what about coastal ecosystems such as mangroves? These swamps store large amounts of carbon in their thick, gelatinous mud. They cover just 0.5% of marine areas, but are among the largest carbon sinks in the ocean. Typically, they store up to 15 times more carbon per hectare than terrestrial soils, absorbed over hundreds or even thousands of years, and sequester carbon 10–50 times faster than terrestrial forests.

Sadly, between 30% and 50% of mangroves have disappeared in the past 50 years; about 30% of the world's seagrasses are gone; and half of the global coverage of salt marshes has been destroyed. Stresses include agriculture run off, fisheries and of course straight out land clearing. As well as storing carbon, mangroves are fish hatcheries. A greater emphasis needs to be placed on their preservation in climate talks and controls on the local and global scale.

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