This Tidal Life

The impermanence of colonisation

The Solway Firth has been described as 'one of the most aggressive estuaries in Britain' and its last wildernesses. Scientist and novelist Ann Lingard, scours the hard and soft edges of this waterland, revealing geologic and cultural layers that are constantly shifting in time with the sea.
is a retired scientist and novelist and has written about the countryside; for many years. She lives on a small-holding in NW Cumbria. Her latest (non-fiction) book is The Fresh and the Salt: The Story of the Solway (Birlinn Books 2020) Her blog about writing, science in art, and other matters is at Eliot and Entropy; and she blogs about the Solway at Solway Shore-walker 
As the incoming tide washes the transparent larvae towards the shore, these microscopic animals have as yet no control over their own existence: whether they will live to metamorphose and grow, or whether they will fail to find the necessary substratum and die. When the tide is slack and the pull and push of the waves diminishes, each larva’s beating hair-like cilia propel it onto the rocks where it might construct its home – for this young piddock is a ‘boring bivalve’, a mollusc with two shells like a mussel, who prefers to find safety by tunnelling into rock. 

But this is the Solway Firth several thousand years ago: for three or four millennia since the glaciers began to melt, the level of sea relative to the land – and so the width and depth of the ‘Solway’ – has been changing. There was a forested plain, and then the roots of the trees were drowned as the peat-bogs grew; and then gradually, sometimes hesitantly, sometimes retreating, sometimes flooding in with great force, the sea won and reached far inland on both shores. The waves uncovered the relict glacial moraines, or scaurs, and shifted sand and shingle, and nibbled away at the banks of peat that were exposed along the subtidal margins.

And so it was that some of those ciliated piddock larvae bumped up against a substratum that was softer and more welcoming than rock, and hung on with their muscular feet and started to bore. As the animal bored, it extended its muscular siphons out of the tunnel’s entrance, and filtered the circulating seawater for oxygen and food. The piddock and its shells grew and, trapped by the narrow mouth of its tunnel, it couldn’t leave and start anew. When those piddocks colonised the peat-banks and for how long, we don’t know; at the next and subsequent iterations of sea-level rise, those thick banks of peat that were riddled with their homes were buried beneath the sand and shingle, preserved out of sight beneath the new, high shores. The sea-level gradually fell again and we now see those pebbly former shore-lines, the ‘raised beaches’, in the eroded faces of the sand-dunes. 

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The wreck on Ship’s-Keel Scaur, with a colony of honeycomb worms, Sabellaria (photo: Ann Lingard)

In late summer and early autumn, the Solway carries another influx of transparent planktonic larvae, each about eighth of a millimetre long, delicate, swirled to and fro by the currents in the sea. These are larvae of the honeycomb worm, Sabellaria; there may be tens of thousands of its peer group in the sea around it, all needing to touch down on solid ground, and all at risk of being swept up and eaten by other filter-feeding invertebrates like mussels, sea-anemones and even other sessile worms. The larvae are stimulated to colonise wherever they ‘smell’ the cementing secretions of others of their kind. They settle on other Sabellaria tubes, they pile in next to each other, and each forms a protective tube around its body by glueing sandgrains edge to edge. Sometimes they construct a disorderly network of tubes, sometimes the tubes are straight as organ-pipes. It is the communal nature of the tube-building, the massed apartment blocks, the high-rises and the sprawling suburbs, that makes Sabellaria so extraordinary.

We don’t know when the honeycomb worms first arrived on the Upper Solway’s Cumbrian shore, but they must have come much more recently than the piddocks: the first arrivals need to build on a hard substratum, like the fields of scattered rocks and smooth pebbles of the scaurs. At Allonby they have changed the nature of the lower intertidal shore, creating sculptural shapes and reefs – known locally as sand-corals or popple – that trap the receding tide in shallow lagoons. The worms re-engineer the middle intertidal zone and allow lower-shore animals to colonise.

To walk the shores of the Upper Solway is to walk through horizontal bands of colour and texture … an ever-changing ribbon of water 

To walk the shores of the Upper Solway is to walk through horizontal bands of colour and texture – wide expanses of sand and shingle; an ever-changing ribbon of water whose colours change from blue to milky-brown depending on the wind; and, above all, the huge skies. The profile of the shore continually alters, and the scaurs – originally deposited by glaciers, are constantly being hidden or re-exposed. For the past few years I’ve been watching the destructive changes that the sea is causing to the remains of a wreck – it’s thought to be a ship’s keel, and has given its name to Ship’s-Keel Scaur (the naming of the boulders and scaurs is itself an interesting part of the coastal heritage that’s being lost). It is an ancient, rock-hard baulk of oak, anchored by a large chain, rust spalling off its surface in bright red flakes. And it has provided a safe haven for mussels, predatory dogwhelks, barnacles and the green lettuce-y sheets of Ulva, as well as, surprisingly, another small colony of Sabellaria.

It’s hard to imagine, now, how busy the Firth would have been between the late 17th and early 20th centuries: there were herring boats, salmon boats, packet-boats, passenger ferries, sailing boats carrying timber, coal and rum, paddle-steamers carrying emigrants, and steam-tugs. But where there are ships, and shifting sandbanks and river mouths, there will also be wrecks. Admiralty charts still mark ‘Changeable Depths’ in the Upper Solway, the sandbanks and channels constantly migrate and shape-change, and the waters often carry a heavy burden of sediment. Most of the smaller ports silted up and the many ship-building businesses declined. And with the construction of the railways, it became cheaper and safer to transport goods by land, away from the hazards of the weather and the tides. The era of sea-transport on the Solway has almost ended and local experience of the sea – as an important focus of human livelihood, a route, and a source of food – is vanishing.

Ship-breaking at Allonby, Cumbria: a hulk being towed in to the shore (Scan thanks to John Whitwell at the Maryport Maritime Museum)

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In the late 1860s, the Solway Junction Railway was constructed – slowly, soggily, and with a great deal of difficulty – across the ‘Moss’ or raised peat-bog near the edge of the Solway at Bowness. Even more daringly, a viaduct was built over the Firth to carry the railway across to Annan on the Scottish side. The purpose of this grand Victorian infrastructure project was to transport haematite – iron ore – from West Cumberland to the furnaces in SW Scotland; by cutting out the dog-leg from Carlisle to Gretna, the transport costs would be much reduced. There were 192 piles buried in the bed of the Solway onto which the viaduct’s cast-iron pillars were bolted and, in a part of the Firth where the shores are soft-edged and labile, it’s very likely that these man-made structures were soon colonised by those marine organisms and algae that needed a hard surface on which to settle and grow. (Very likely, because when a wind-turbine on the Robin Rigg sandbank in the Solway was removed a few years ago, its underwater section was seen to have become an artificial reef, coated with mussels, sea-anemones and starfish.) 

But all did not go well with the viaduct; the fast-flowing tides sucked away the supporting sediment and scoured pits around the piles; massive ice-floes in the winter of 1881 smashed large sections of the structure; and subsequent cheap imports of haematite from Spain meant the railway was no longer economically viable – so the railway and the viaduct were eventually broken up and removed. Some of the foundation piles still remain and are exposed during the very lowest spring tides.

Remaining pillars of the Solway Railway Viaduct at Bowness-on-Solway (Photo: Ann Lingard)

The Firth is a place where the layers of time – geological time – might be understood by reading the rocks and by wandering the shores: the ‘hard’ shores on the northern, Scottish, side which originated on another continent, and the soft and shape-changing English shores to the South. Here along the southern shores especially, humans have colonised and actively changed the edges, but there is an impermanence to these constructs that results from economics, fashions and sometimes, counterintuitively, technological advance. These changes are observable in a lifetime, even – in my case – in a couple of decades. But other changes can be observed while the moon’s influence waxes and wanes; changes wrought by the tides and weather. For the Solway Firth is famous for its large tidal range, which can be as great as 10 metres on the biggest of the spring tides. Even on the neap tides, when the range might be only 5-7 metres, this is an enormous volume of water to enter and leave the Firth, twice each day, so it’s unsurprising that the waves and turbulent currents gnaw at the edges and churn the sea-bed. The sand and shingle are always on the move, despite the wooden groynes built at right-angles to the shore, despite the hard concrete coastal defences and gabions filled with stone: groynes are slowly buried, waves hurl pebbles across the coast road, the edges of the dunes are scraped bare. 

The peat that was once home to piddocks and that had preserved the roots and trunks of an earlier forest has vanished, broken up by the autumnal storms. This year the ship’s keel has finally broken in two and is part-buried, its eponymous scaur hidden by sand; soon no-one will remember why the scaur had that name, if they remember the name at all. The haematite mines and the sub-sea coal mines are now part of Cumberland’s coastal history – its coastal ‘heritage’ – like the iron-smelting and steel-making and crowded ports.

Tourism is the newest ‘industry’, and trailer parks colonise stretches of the coast: few people even notice the worm-built reefs or wonder about the grey boulder clay and patches of soft peaty material on the shore. The next industry might exploit that huge renewable source of energy, the Solway’s tides; there are plans and suggestions, but governmental inaction.

The Solway’s long history has been one of changing sea-levels – glacial clay and moraines, forest, peat, multiple layers of beaches – and that will be the story of its future too. The marine environment may well inundate the peatlands of the Mosses in the future, and incoming piddock larvae may find and colonise new homes; honeycomb worm reefs may be suffocated by the shifting sands, and larvae borne in on the tides will have to settle elsewhere. Changes in currents due to tidal power interventions will alter the bathymetry and the mud and saltmarshes of the margins, but the invertebrates and microscopic animals that colonise the edges will shift their neighbourhoods, and adapt – for this is what they have been doing for thousands of years along these shores.

The changes may be due to our activities, directly or indirectly, but ultimately our attempts to ‘civilise’ the Solway will always fail.

The changes may be due to our activities, directly or indirectly, but ultimately our attempts to ‘civilise’ the Solway will always fail. People who work on its edges or on the water recognise that its character is too strong, it is ‘chaotic and unpredictable’, ‘one of the most aggressive estuaries in the UK’, ‘uncontrollable’, ‘one of the last wildernesses’, ‘a  terrifying animal’. There are ‘loads of powerful, hidden things going on underneath the surface’ and, despite our interventions, the Firth will decide.

 

Note:
‘Cumberland’ was joined with Westmorland and part of Lancashire in 1974 and was renamed as ‘Cumbria’

 

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The Autumn 2020 issue is dedicated entirely to fiction, featuring short stories, illustrations and colour artwork
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Dark Mountain: Issue 18 – FABULA

The Autumn 2020 issue is dedicated entirely to fiction, featuring short stories, illustrations and colour artwork
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