On a rocky beach in Cornwall, a group of wetsuit-clad freedivers and snorkellers are wading into the shallows. Below St Mawes Castle, built by Henry VIII to defend Falmouth harbour, they disappear in a swish of florescent pink and green fins.
They are volunteers, trained by the Cornwall Wildlife Trust to use underwater cameras and floating GPS devices to detect changes in marine habitats over time.
Their work is vital because beneath the surface of Falmouth’s busy natural harbour, known as Carrick Roads, are two of the UK’s most biodiverse and carbon-rich marine habitats: lush seagrass meadows and purple-pink carpets of ancient maerl – a rare and fragile coral-like seaweed. They are some of the largest such beds in England.
Parts of the slow-growing maerl beds, which stretch from St Mawes to St Just in Roseland, are believed to be up to 4,000 years old. They act as nurseries for commercially valuable species such as scallops and crab.
Last year, however, divers found a “worrying deterioration” in the maerl beds, which were being smothered by algae, preventing much-needed sunlight getting to the seaweed. Algal blooms, fuelled by excess nutrients from agricultural runoff and sewage in the River Fal’s catchment area, are unfortunately also present today.
Simon Tagney, 65, is a retired TV camera operator turned citizen scientist. “When I went down in March this year, everything looked newly polished and clean,” he says. “But going in today, there’s lot of filamentous algae on everything. A lot of the maerl is obscured by it. You can’t see the detail – it is like going into a dusty room.”
The Cornwall Wildlife Trust is among several environmental organisations backing a new initiative from Cornwall council called Fal Rivers to Reef, which aims to work with farmers and landowners to restore nature, build climate resilience and reduce pollution from the river’s source in Goss Moor, through 22,000 hectares (54,000 acres) of farmland and woodland to Falmouth.
A key driver of the scheme was catchment data from the Department for Environment Food and Rural Affairs (Defra) published in 2022, which identified rural farm pollution and waste from the water industry as the reason the Lower River Fal failed to achieve “good” ecological status. The new initiative aims to improve water quality and protect seagrass, maerl and the last remaining native oyster beds in Falmouth estuary, which are harvested from sail and oar boats.
“The Fal is full of nutrients and that can create mats of opportunistic algae that smothers seagrass like a blanket,” says Matt Slater, marine conservation officer at the trust, which has been forced to temporarily cancel a seagrass restoration project in Ardevora, on the Roseland peninsula, until the water quality improves.
“We know that small changes by farmers can make a big difference in reducing runoff,” he says.
About 14 miles (22km) from St Mawes, at Gare farm, over tea and home-baked cake, the tenant farmers Claire and Martin Tupper talk about their efforts to improve their soil and stop runoff, and the benefit they get from being involved in Fal Rivers to Reef.
“We are not organic but it is the unseen pollution that is a concern,” says Martin, 63. They have long used “herbal leys” – a mixture of grasses, clover, legumes and herbs – to improve soil, cut down on fertilisers and improve drainage. And they have noticed the benefits: the lambs are growing faster and the mix attracts butterflies and dragonflies.
With the council’s help, they have also taken other steps, including relocating a gate away from a slope where it was causing excess runoff.
And they are restoring an ancient orchard, a key source of biodiversity, which had lain neglected “because I was on my own and it wasn’t earning”, says Martin. “We didn’t know how to access that kind of help.”
Claire, 62, says: “You want to do the right thing but you don’t necessarily know the right people to talk to. The support has been invaluable.”
As part of Fal Rivers to Reef, the council runs workshops, get-togethers and recently, a boat trip on the estuary to get farmers, fishers and conservationists to better understand each other’s perspective.
Jason Pascoe, 56, one of a score of native oyster “sail-and-oar” fishers left in Cornwall, says silt washing down the river from development, farming and heavier rain is creating more mud in the river and threatening the fishery.
“One of the biggest problems for the oyster fishery is silt,” says Pascoe. “The oyster shells need to be clean and the larvae need clean substrate to build those shells.”
Chris Jones, a beef farmer, says he has made a big change to his farm that could help Pascoe and his fellow fishers if taken up more widely.
Small Changes by Farmers and Fishers Could Save River Fal