Blue carbon: how three Australian marine sites lock away 2bn tonnes of CO2

Greenhouse gas stored in country's marine world heritage sites about same as four years of national emissions

Three of Australia's world heritage-listed marine sites have more than 2bn tonnes of carbon dioxide locked away in their vast seagrass meadows, coastal mangroves and tidal marshes, according to a new report from a UN agency.

Unesco has for the first time calculated all the so-called blue carbon" stored across its 50 world heritage marine sites and finds they contain about 5bn tonnes of CO2 and other greenhouse gases.