Maerl the size of nearly 900 rugby pitches in Fal Estuary

Cornwall Council commissioned the University of Exeter and environmental researchers Natural Capital Solutions to carry out surveys off the coast near Falmouth and Penzance, to assess how effective seagrass and seaweed are at growing and storing ‘blue carbon’ in an effort to tackle climate change.

As part of the Blue Natural Capital Project, scientists discovered that the Fal and Helford Estuary Special Area of Conservation supports a vast seabed of maerl - a rare and ancient seaweed - equivalent to the size of nearly 900 rugby pitches.

The living habitat carpeting the seafloor is thought to be up to 4,000 years old and provides protection for many small marine plants and animals.

It is also extremely efficient at storing carbon at an estimated rate of 841 tonnes or CO2 annually - the equivalent to nearly four million petrol car miles a year - and five times greater than that absorbed by the combined area of seagrass, kelp and saltmarsh also in the catchment.

This is the first time the full extent of the maerl beds and the organic matter stored in the conservation area has been measured, with the discovery now marking the location as a key national site for this irreplaceable blue carbon habitat.

The discovery has been made in the Fal and Helford Estuary in Cornwall (Image: David Davies/PA)

Dr Chris Laing, senior lecturer in marine biology at the University of Exeter, and research lead on the project, said: ‘‘Maerl has not been considered as a valuable carbon store to date, but our research demonstrates that as well as being a rare and valuable seabed habitat it should be a key player in coastal blue carbon assessments, which is an extremely important discovery for Cornwall where the extent of the maerl beds are significant.”

The council is working with the university and other organisations such as Falmouth Harbour and Ocean Conservation Trust, to protect the valuable ecosystem from threats such as anchor damage, swing moorings, nutrient discharge and sea surface temperature increases from climate change.

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Cornwall’s cabinet member for environment and climate change Cllr Martyn Alvey said: “I love being on the water around the Fal and am astounded to now discover the true extent and importance of the maerl beneath the waves.

“This invaluable research has increased our knowledge of this ancient seaweed and its ability to store large quantities of carbon for centuries to millennia, highlighting its importance as a natural solution in tackling climate change.

“The project shows how these blue carbon habitats can help us in our response to both the climate and ecological emergencies if we properly protect them and allow them to fully recover.”

Alongside maerl, other habitats including seagrass, saltmarsh and kelp are known to be valuable blue carbon stores.

The Blue Natural Capital Project, funded by Defra and the Environment Agency’s Natural Environment Investment Readiness Fund (NEIRF), has improved knowledge on blue carbon in Cornwall to provide a clearer understanding of its qualities, location and a baseline of evidence to help unlock future private funding for the natural resource.

The information found by the project will help Cornwall Council and its partners direct the next stages of blue carbon research and support the development of national blue carbon policies.