Blue carbon – Arran’s seas and climate change

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The Community of Arran Seabed Trust (COAST) is running a year-long media campaign to raise awareness of the many exciting habitats and species to be found in Arran’s seas, many protected by the South Arran Marine Protected Area.

Their latest article is all about blue carbon which they felt was very topical given current COP26 conference. There is more information on COAST’s social media or visit


In May 2019, the Scottish government declared a global climate emergency in response to climate change linked to elevated levels of carbon dioxide (CO2) in the atmosphere.

With Glasgow currently hosting the United Nations Climate Change Conference (COP26), there has been a lot of attention on climate change and the personal and collective actions that we can take to ensure a habitable planet for the future.

Whilst we need to reduce the amount of greenhouse gases we produce, measures to remove greenhouse gases from the atmosphere – such as protecting and restoring natural areas – are being seen as an increasingly important part of an overall strategy to tackle climate change.

Some habitats on land, such as rainforests, woodland and peat bogs, are known as being very effective at removing CO2 from the atmosphere as plant tissues and soil can lock in carbon.

However, Scotland’s marine habitats and species have received far less attention for their role in combating climate change.

Arran and Scotland’s seas contribute to tackling climate change in many ways, although some of these have negative consequences.

Seawater absorbs CO2 and heat from the atmosphere: up to a third of the CO2 released into the atmosphere and around 93% of the heat produced as a result of greenhouse gases are being absorbed by our oceans.

While this might seem to be a positive thing, warming seas are affecting marine life and our climate and consequently species on land too, and our seas are becoming more acidic as the absorbed carbon dioxide forms carbonic acid.

While we cannot just continue to see our oceans as a sponge that can suck up excess heat and greenhouse gases, supporting the ability of marine habitats and species to capture and store carbon as part of their natural function is something we need to encourage.

Results of ongoing research, both in Scotland and further afield, are increasing our understanding about the critical role our marine habitats and species play in capturing and storing carbon; as well as informing us about the management decisions required to ensure that the captured carbon in coastal and marine ecosystems – so called ‘blue carbon’ – actually stays locked up into the long term.

In blue carbon ecosystems, carbon is captured in the living tissue of marine animals and plants and also in their shells and skeletons, such as the shells of scallops and lobsters and coralline seaweed such as maerl.

A lot of carbon-based material also gets washed into the sea from the land and this, along with material from marine habitats and plants, can become stored within seabed sediments which then act as a carbon sink and lock the carbon away, potentially for thousands of years.

The process of capturing carbon in long-term carbon stores is known as carbon sequestration.

Many of Arran’s marine habitats and species, that have featured in articles in the Banner this year, have an important role to play in capturing carbon.

Although the Lamlash Bay No Take Zone (NTZ) and South Arran Marine Protected Area (MPA) were initially established to recover and protect marine life, they are also providing important protection for blue carbon habitats such as kelp and other seaweeds, seagrass beds and mud.

A study of Scotland’s MPAs estimated carbon capture and storage in the South Arran MPA at 8,046 tonnes per km2 – a total of 2,245,047 tonnes of carbon for the MPA!

How much carbon is captured and stored by various different marine habitats and species is currently a very active area of research.

With marine carbon sequestration estimated at potentially more than double the amount of carbon removed by habitats on land, the marine environment clearly has a significant role to play in our efforts to address climate change.

But it can only do this if we look after it and provide more effective protection for marine areas.

If marine ecosystems are damaged or degraded by human activities, their ability to capture and store carbon is significantly reduced or lost.

Stored carbon in seabed habitats can be released into the atmosphere by physical disturbance, such as can occur with coastal and marine developments, and through activities such as trawl and dredge fisheries.

Such activities can result in release of substantial amounts of carbon, with experts estimating as much as 1.02 billion tons of CO2 is released annually from degraded coastal ecosystems.

Earlier this year, findings of a study reported that global trawling releases as much CO2 as air traffic.

With marine carbon sequestration in the UK having an estimated value of £57.5bn annually, improved protection for blue carbon habitats makes economic sense.

Alongside calls for improved protection of our seas, there is increasing interest in active restoration and enhancement of marine habitats to achieve multiple benefits, including protecting blue carbon areas.

There are projects underway in Scotland exploring the potential for restoration of seagrass and native oyster beds.

The South Arran MPA and waters around Arran provide potential opportunities for similar initiatives locally.

We know that local communities have the power to demand and effect change, and will continue to work with the community on Arran to help drive our collective responsibility to tackle climate change.