Rewilders of our seas – bringing back oysters and seagrass

Gamble described to me the vanishing of that important mollusc. Across Europe, the European native oyster population has declined by 95%. It has all but disappeared in areas of Scotland in which it once abounded: the Firth of Forth, for instance, was home during the 19th century to the most productive oyster reefs in the country. During its peak production, Gamble notes, 30 million oysters were being landed per year.

The oyster could now be set for a return – with numerous reintroduction projects around the UK, including Gamble’s, which last year began its work on two sites in the Firth of Clyde: Largs Yacht Haven and Fairlie Quay Marina.

The Wild Oysters Project

The Firth of Clyde, she said, was chosen because there is historical evidence of European native oysters and also two remaining populations. “We’re not sharing where those populations are,” she said. “They’ve already been quite fished and are under threat from illegal harvesting.”

Gamble’s assessment of our role in the oyster’s demise is stark. “We believe the decline of the oyster is mainly down to human activity – pollution, habitat loss, over-harvesting and disease,” she said. “Historically people ate a lot of oysters. They were once a staple part of the food source for working populations and they were very cheap and plentiful up until the 19th century. Roman soldiers consumed oysters while building the Antonine Wall in the second century.”

The story of this species’s decline and the attempts to reintroduce it is also a key chapter in a new book, Rewilding The Sea: How To Save Our Ocean, by Charles Clover.

What’s striking about Clover’s book is that, unlike his previous book and documentary, The End of the Line, this isn’t an account of relentless bad news. Alongside its damning exposure of our human impact on ocean life, it finds “tendrils of hope”. It describes the possibilities of what can happen when areas of the ocean are properly protected, restored and allowed to thrive.

And the oyster is a key element. Clover highlights this species because of what it tells us about the story of our relationship with the life within the sea – what we have done wrong, how we can pull back from that, and why protecting what we’ve got and allowing it to expand is even more important than replanting and resowing.

“Why is the oyster story different from the story about fishing which I’ve told in my previous book?” he says, as he speaks to me ahead of an appearance at Edinburgh International Book Festival on August 22.

“People will tell you that the oyster has so many factors in its demise – disease, pollution, predators. But when you actually read the research papers you discover over-fishing of oysters is one of the earliest and biggest instances of over-fishing. It’s not just an incidence of it in the UK, where we’ve been able to rake beyond the wade-able margins, where we first overfished the oyster, for a thousand years. Everywhere else in the world ... all these other species of oysters, the Australian ones, the American Pacific ones – they were just mined out.”

Clover, a former Telegraph journalist, has been an important driver in the creation of marine protected areas through the organisation he set up, the Blue Marine Foundation. One of the foundation’s recent wins, through suing the government, was the banning of bottom trawling and dredging from the huge marine protected area around Dogger Bank. Some years ago, Clover recalls, Blue Marine began looking at oyster restoration and asking whether it might work. One of his concerns was that even if they could be reintroduced, would they just be fished and over-fished again? Would it be just another “tragedy of the commons” repeated all over again?

Protection, he tells me, is key. “The only reason is might possibly work is because there are now places where the tragedy of the commons does not happen. They are called marine reserves, marine protected areas. Now, it helps if those marine protected areas are actually protected, which in places in Scotland they are not. In the offshore waters in particular they are not.”

In recent years the Blue Marine Foundation and its partners have restored 105,000 native oysters to the Solent, an area which, says Clover, “had been completely stuffed”. As recently as the 1970s, he observes, there were around 700 people working in the oyster fishery, but by the time of its closure that had dwindled to around half a dozen. “That’s an astonishing overfishing story of poorly enforced regulation”

Hence, marine protected areas were key to bringing the oysters back. “Virtually all the way along the Solent in the coastal waters there are protected areas, so there’s always going to be some oysters people can’t get,” he says. “That’s what convinced me to do it.”

Clover describes the oyster as “not just a species, but a habitat”, adding that “some 466 other species are associated with the European native oyster and nobody knows why. We found, in these cages we suspended in marinas, all sorts of things cropping up – like European eels and seahorses. I mean, what was a seahorse doing in an oyster cage in a slightly murky marina? If you want to bring back species, if you want to bring back fecundity, if you want to let nature rip, you need oysters.”

Author Charles Clover

Among the many sites across the world where oysters were wiped out is New York, where there is archaeological evidence that Native Americans had begun decimating the populations long before the Europeans arrived and took it to a new level. However, though nearby Chesapeake Bay may be a depressing story of loss, it’s also a tale of hope. For Chesapeake Bay has trail-blazed the way in terms of oyster and other marine habitat restoration.

Both Chesapeake and the Blue Marine Foundation’s work were among the inspirations for what Gamble and the Wild Oysters Project is doing in the Clyde. When I spoke to her last year, the project was about to introduce “oyster nurseries” at its two sites, each containing 27 mature oysters, old enough to reproduce – which would later, in the summer months, start to release oyster larvae that would be carried out into the Firth of Clyde.

This month Wild Oysters Project published the results of research carried out mostly by volunteer citizen scientists, who have over the past year monitored biodiversity in the nurseries. “A total of 3,637 individual mobile organisms (inclusive of semi-mobile blue mussels and crinoids),” they announced, “have been observed in the Largs Marina sites from June 2021 until June 2022. These comprise of 19 identified species and several unidentified species. The most abundant organisms were brown shrimp (Crangon crangon), accounting for 30.30% of the total, followed by red feather stars, accounting for 21.50% of organisms.”

The demise of the oyster around the east coast is a story that the eminent historian TC Smout has analysed in his book, The Firth of Forth: An Environmental History, and other academic papers, all of which make gloomy reading. “The evidence from the 19th century is of a wealth of natural marine resources scarcely to be guessed at today,” writes Smout. Oysters are just one example he quotes, citing “scalps” covering 50 square miles in the Firth.

“All this abundance has gone,” he adds, noting that oysters were thought to be extinct in the area until a few were found alive by a scientist in the autumn of 2009. Catches fell from 8.6 million in 1867 to 370,000 just 10 years later and 60,000 in 1887.

Bringing back lost life to the Firths of the Forth and the Clyde is now the aim of a number of restoration projects. Among them is Project Seagrass, co-founded by RJ Lilley, an enthusiastic advocate for ecosystem restoration and also a big fan of Smout’s analysis. “If you read Smout’s book,” he says, “51% of the intertidal in the Firth of Forth has been removed. The Firth of Forth has been straightened, peatlands have been drained, the sediments come down the channel, you know, all the space that would have been the salt marsh, the seagrass and those coastal habitats – that’s shrunk by 50%.”

What Lilley is most passionate about is communicating the state of our planet. Hence, for him, seagrass is about more than seagrass.

“It’s a great ecosystem,” he says, “and it’s a great vehicle for engaging people in the plight of the oceans, but it’s about nature more broadly. It’s one of those few marine ecosystems you can find really close to the shore, it’s global and it’s a plant, so people intuitively understand how plants work in a way they don’t native oyster spats.”

His journey in seagrass began when he was a science teacher. Having moved to Swansea, he met Dr Richard Unsworth, an academic he describes as “Mr Seagrass”, and started reading Unsworth’s papers on the subject. He recalls thinking at the time: “If I, as a biology teacher and a diving instructor, haven’t heard of this habitat or have only recently heard about it, then who has heard of it?”

Two years later, he and a friend set up Project Seagrass, and six years ago he moved to Edinburgh – partly because his mother came from the city but also because the little data there was around seagrass distribution “was pointing towards Scotland having way more seagrass than the rest of the UK by a long shot”.

The decline in seagrass meadows appears to have been almost as devastating as that of oyster populations. One of the figures sometimes quoted for its loss around the UK is 92%. “That’s the worst-case scenario,” says Lilley. “It’s probably at least 50%. But there’s very little data so the extrapolation is tough to make there, but either way, we know we have significant loss.”

One of the problems, Lilley notes, is that we do not know where many of the remaining meadows are. They have not been mapped. Hence Project Seagrass has also created an app so that citizen scientists can help spot and plot its distribution – for more important than sowing new meadows is protecting what is there, which can only be done if we know where it is.

Seagrass and oysters often come together (Lilley describes seagrass as Robin to the oyster’s Batman) and notably the Scottish community-based seagrass project he is working with, Restoration Forth, does not just revolve around seagrass. There are oysters too, the introduction of 30,000 of them, which will be co-ordinated by Dr Bill Sanderson, Associate Professor of Marine Biodiversity at Heriot-Watt and the man behind a project that has been restoring oysters to the Dornoch Firth, the Dornoch Environmental Enhancement Project (DEEP).

In the Dornoch project, which last year marked the completion of 20,000 native European oysters being returned to an area where they became extinct more than 100 years ago, DEEP have been creating entire protected reefs where they have been lost, carefully placing thousands of oysters on new reefs created from waste shell to mimic their natural habitat. The hope is that the population will build to up to four million, spread over 40 hectares in the coming years.

Lilley also mentions one other marine habitat around which there is a rewilding movement in Scotland: saltmarsh. It’s one that “always gets missed out,” he says, “but from a climate change perspective that’s the big one”.

Many of us are well aware of the story that sequestering carbon is behind the drive to plant trees and rewild vast areas of our landscape, as well as peatland restoration, but fewer are aware of blue carbon and the potential to create carbon sinks between our seas and coastal areas and the roles of saltmarsh and seagrass in that story.

“Blue carbon,” Lilley says, “is everything in the marine space where carbon is sequestered, everything from whales dying or whales pooing, to sea grass and salt marsh. Seagrass and salt marsh accumulate carbon in a quite similar way and it’s the carbon that’s being buried in the sediment, as opposed to any carbon actually in the plants themselves. Imagine you walk across a salt marsh, you walk through seagrass meadow in the UK, there’s very little biomass actually above ground. The excitement is that the carbon is stored in the sediments for long periods of time.”

Saltmarsh at Loch Fyne, photographed by Professor Bill Austin

In Scotland, and indeed the UK, the key expert in saltmarsh is Professor Bill Austin at St Andrews University, a scientist who is not only leading the way in research in the habitat, but also the chair of a Blue Carbon forum in Scotland. What strikes me chatting to him is his sheer love of saltmarsh. He enthuses, “As a scientist I just like being on salt marshes. They’re peaceful places. I feel good when I’m working on them and these are all things that are difficult to value sometime”.

As with seagrass, we don’t know exactly how much saltmarsh we have lost in recent centuries. Shockingly, however, Austin quotes estimates that we have probably lost “more than half of this habitat in probably the last two decades, a lot of that through agricultural land reclamation”.

Their value as ecosystems, however, is now not only being appreciated, but counted and assessed, for, as Austin points out, in March, the UK Climate Change Committee made some recommendations ot the government that it should move ahead to include these two so-called blue carbon habitats in the UK National Greenhouse Gas Inventory - just as peatlands were incorporated.

Essential in making this possible is some of the work Austin is doing. “Before that can really happen we have to map and understand the flows of carbon in and also out of these habitats. So one of the challenges in terms of the evidence at the moment is not only how much carbon do they take in and store, but how much carbon can they release back to the environment. And that’s a scientific evidence question, an evidence gap.”

What’s good about saltmarshes is that they are now well mapped as a result of Austin’s work, and that, again of citizen scientist across the country who sent in samples and gathered data through his project’s Saltmarsh app. With seagrass, he observes, it’s a slightly different story, because of their distribution is partly subtidal, which is why efforts like Project Seagrass’s to map it are so important.

ONE of Clover’s stories in Rewilding the Sea captures that sense of abundance lost. He describes witnessing a rare “boiling” of mackerel off Mull, when the fish rushed inshore, turning the sea alive with movement. “I’ve never seen anything quite as elemental as that. Everybody thinks that the sea is wild, from the moment you step into the salt water, and of course, to an extent that’s true because it’s not cultivated, but it’s not true in the sense that it’s not a fully-functional ecosystem because we have spent hundreds of years, with industrial methods, suppressing it.”

The story of what we humans have done to our seas is a shocking one. But Clover, nevertheless, sounds optimistic. He talks about “multiplying examples of tendrils of hope”.

“We’ve got the potential to restore our seas – actual rewilding going on a month ago off Dogger Bank, and in Lyme Bay [resulting in] four times the number of species when you stop trawling and dredging.”

Still more important than reintroduction is that we protect what’s still there in our seas.

Too often, after all, it’s been a story in which we haven’t known what it had got, because we never saw it until it was gone.

Charles Clover & Laline Paull: Secrets of the Ocean is at the Edinburgh International Book Festival on August 22