Context

Three World Heritage-listed marine sites in Australia store more than 2 bn tonnes of carbon dioxide locked away in their vast seagrass meadows, coastal mangroves and tidal marshes, reports UNESCO.

About

The Report

• The UN organisation has released its first global scientific assessment of ‘blue carbon’ ecosystems, which double as World Heritage sites.
• This was the first of its kind to quantify blue carbon -- carbon dioxide.
• The report quantifies the enormous amounts of so-called blue carbon absorbed and stored by those ecosystems across the world’s 50 UNESCO marine World Heritage Sites.

Key-highlights of the Report

• Australia’s six marine World Heritage Sites hold 40 per cent of the estimated 5 billion tons of carbon dioxide within UNESCO sites.
• 2 billion tonnes of carbon dioxide are locked away in three sites. The three sites mentioned are the: 
  • Great Barrier Reef in Queensland: The Great Barrier Reef holds the biggest stocks of blue carbon across all the 50 world heritage marine sites, according to the data: 1.8bn tonnes of CO2-equivalent (C02-e).
  • Shark Bay in Western Australia: Shark Bay is estimated to store 164m tonnes of CO2-e, mostly in 342,000 hectares of seagrass.
  • Ningaloo coast in Western Australia: The Ningaloo coast world heritage area is holding on to 4.6m tonnes of CO2-e, also mostly in its 26,000 hectares of seagrass.
• Although the sites make up less than 1 percent of the planet’s oceans, they house 15 percent of blue carbon assets in their seagrass meadows, tidal marshes and mangroves.
• The areas are called ‘carbon sinks’.
  • Carbon sink is a term used to describe reservoirs of either vegetation or water which store carbon for an indefinite period of time.

Significance of blue carbon ecosystem

• Although blue carbon ecosystems represent less than one percent of the global ocean area, they store about half of the carbon dioxide via the world's oceans, absorbing carbon 30 times faster than rainforests.
• But if these blue carbon ecosystems are not conserved, they could increase global carbon emissions.
• While they're healthy, blue carbon ecosystems are excellent stores of carbon dioxide.
• But if they are damaged, they can release huge amounts of carbon dioxide stored over millennia back into the atmosphere.