Seagrass sequestration

In a new report from the International Union for Conservation of Nature (IUCN), scientists have documented the capacity of coastal habitats to bury and lock away carbon into soils and sediments.

The report outlines how seagrass meadows, mangroves and salt marshes have a much greater capacity to trap carbon than land carbon sinks, potentially storing 50 times the amount of carbon that tropical forests do on a per-hectare basis.

These revelations have led the IUCN to believe that ocean ecosystems are essential to combating global warming, said Dr Hilary Kennedy from Bangor University’s School of Ocean Sciences.

While the role of forests and peatlands in carbon sequestration has been relatively well documented, surprisingly little has been made of the role that coastal habitats play in storing carbon.

Kennedy said: ‘Although seagrass meadows cover a relatively small portion of the ocean (around one per cent), they constitute an important carbon sink, responsible for about 15 per cent of the total carbon storage.’

At the recent Copenhagen Climate Change Conference, Carl Gustaf Lundin, head of the IUCN’s Global Marine Programme, also drew attention to the capacity for coastal environments to lock away carbon for thousands of years.

He emphasised the importance of seagrass meadows, saying that seagrass meadows may well be more effective in sequestering carbon than forests, and said that investments in protecting coastal ecosystems might be a very cost-effective way to sequester carbon.

Kennedy added: ‘In addition to the benefits of carbon sequestration, seagrass meadows also perform other functions in the ecosystem such as providing nursery grounds and food for coastal food webs, sediment stabilisation, wave attenuation and shoreline protection.’

However, many of the coastal habitats, including seagrass meadows, are under significant threat from development and degraded water quality. A recent assessment has found that seagrass meadows have been disappearing at a rate of 110km2 each year.

Part-funded by Natural England, the Lighthouse Foundation and the UNEP, the IUCN report ‘The Management of Natural Coastal Carbon Sinks’ looks at a range of global options for carbon management around the world’s coastlines.