The ACA Forum

Conserving the Devonshire Avon from source to sea


The order designating the Avon Estuary as a Marine Conservation Zone (MCZ) may be found here:- Designation order for MCZ, Avon Estuary



Have you ever been up to your neck in that black, gluey and smelly mud which abounds in the upper reaches of the Avon Estuary and around the salt marsh areas – thinking you might never escape its clutches and, somehow, might have to call the Coastguard for rescue if only you could get your hands free of the stuff?    If so, you might want to withdraw your curses and instead sing its praises, rather like the old Flanders and Swan song – “Mud, Mud, Glorious Mud” – because, with the recent renewed level of interest in global warming, that black goo has now been reinvented as ‘Blue Carbon’.




According to the website at, ‘Blue carbon’ is the carbon stored and sequestered in coastal ecosystems such as mangrove forests, sea grass meadows or inter-tidal salt marshes. These valuable ecosystems hold vast carbon reservoirs; they sequester atmospheric CO2 through primary production, and then deposit it in their sediments. In fact, most blue carbon is found in the soils or sediments beneath the vegetation.

The rates of carbon sequestration and storage are comparable to (and often higher than) the sequestration rates in carbon-rich terrestrial ecosystems such as tropical rainforests or peatlands. Unlike most terrestrial systems, which reach soil carbon equilibrium within decades, deposition of carbon dioxide in coastal ecosystem sediment can continue over millennia. However, when these coastal ecosystems are degraded or destroyed they can become carbon dioxide sources due to the oxidization of biomass and organic soil.

Because coastal ecosystems do contain substantial amounts of carbon, and because this carbon is in danger of being released, they are important in mitigating climate change. Unfortunately, however, the rate of loss of mangroves, seagrasses and saltmarshes (driven mostly by human activities) is estimated to be among the highest of any ecosystem on the planet, prompting international interest in managing them more effectively for their carbon benefits.

Although the Avon Estuary’s contribution to carbon sequestration may be small on a planetary scale, that contribution to conservation strengthens the argument for its designation by Natural England as one of the new Marine Conservation Zones and for the inclusion of the embryonic salt marsh at South Efford within its boundary.

Those anaerobic bugs thriving in the mud, locking up carbon, could be the saviours of our planet.  Disturb them at your peril!!! GLORIOUS MUD indeed!


Click here for a link to the Devon Wildlife Trust’s video showing some of the salt marsh and mud flats in the upper estuary as of Autumn 2018:-