When the 12th Earl of Strathmore, a 19th-century nimby who made an immense fortune from coal, refused to allow trains across his Gibside estate, the North Eastern Railway adopted an expensive alternative route via four viaducts and a cutting. After the line closed in 1962 it became the Derwent Walk Country Park, beloved by ramblers, runners, dog walkers, cyclists, horse riders and birdwatchers.
The view from the parapet of the Nine Arches viaduct, spanning the River Derwent’s gorge, is exhilarating: a vibrant pointillist canvas of a tree canopy, painted with bursting leaf buds; an earthbound opportunity to see woodland from the perspective of the red kite that soared over my head this morning.
At the western end of the viaduct, the path enters the long cutting. Its steep, wooded banks are bright with primroses, golden saxifrage, wood anemones and violets. Hidden among them, I found rough horsetail, or Dutch rush, a living fossil whose antecedents thrived in the Carboniferous period, 300m years ago, long before flowers evolved.
It’s a leafless, flowerless, knee-high thicket of green, hollow, corrugated stems, thinner than a pencil. In spring, some are tipped with bullet-shaped spore cones, clothed in tiny polygonal tiles that separate and release microscopically small wind-borne spores, each with four arms called elaters that unwind and act as sails. One of evolution’s minimalist efforts, but what a story it has to tell.
Horsetail stems have a high silica content, so fossilise well. Fragments of rough horsetail’s giant ancestors, some as tall as today’s forest trees, once trundled past here in railway wagons, embedded in the millions of tons of coal they transported from Durham coalfields to colliers moored at staithes on the Tyne.
Since the Nine Arches viaduct was built, Gibside Hall – the Strathmore stately home – has become a romantic ruin, now in the care of the National Trust. Coal-based industries that once filled this rewilded valley lie hidden under woodland, lakes and cowslip-filled meadows. But rough horsetail endures, a living testament to a tropical landscape of giant horsetails that still influences our lives. Carbon dioxide released from burning these disinterred ancestors is changing the climate of our planet.
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