Celebrating the Wild Side of Yorkshire’s Coast & Country:
The Grey Sentinel of the Riverbank rules the roost over the hybridising ecology
Overhead a heron calls, its loud, harsh grating and large-winged almost ponderous flight remind me of something prehistoric; almost a living embodiment of a pterodactyl. The grey heron was once so numerous in Yorkshire, that in 1466, for the feast to celebrate the enthronement of the Archbishop Neville, 400 ‘hernshawes’ or baby herons, were taken for the pot. (So if you have the family name ‘Hernshaw’ you now know its origin!) Grey herons often breed in colonies and up to twenty-five nests have been recorded in a single tree. Remarkably, the eighteenth-century Welsh naturalist and traveller Thomas Pennant claimed to have seen eighty nests in a tree near Spalding in Lincolnshire. Heronries can involve hundreds of birds, and surprising to many people, in the north of Britain, they are frequently on sea cliffs. Recently up in Northumbria I saw many herons over the sea and hunting around the abundant and teeming rock pools.
Photograph by Chris Percy
However, the heron has not always had such a good time. By the early 1970s, with water pollution, persecution, and habitat destruction, all topped off by DDT pesticides, the English population of grey herons reached its lowest point for centuries. Yet now they are back and thriving, although perhaps not all anglers are too keen to see them in quite such numbers. However, like the handsome kingfishers, most fishermen and other river users are pleased by their return.
I always think the scientific name of Ardea cinerea is wonderfully evocative for what is our most widespread, large, predatory bird. Today the sight of this magnificent almost pterodactyl-like creature is as familiar over our Yorkshire city centres as it is in wetland nature reserves. On the urban River Don for example, there is now a winter afternoon roost of herons close by the Hillsborough football ground. Near Kelham Island Industrial Museum, an area smashed by the 2007 floods, the herons circle the ancient weir and drift effortlessly close to the balconies of the recently refurbished upmarket urban apartments. The residents of these now highly desirable properties look out over a scene that twenty years ago, was both biologically dead and a social no-go area.
The view today is of a clean river rich in fish life, birds and mammals. Yet in this recombinant urban ecology, exotic Japanese knotweed reigns supreme whilst underneath its dense shade grow bluebell and wood anemone. There are efforts now to curtail its spread and claw back some riverbank from knotweed and Himalayan balsam.
The spectacular flowers of giant hogweed – a metre or more across
The ecological process is itself interesting as native and alien jostle for territory and possession. Buddleia, knotweed, balsam, sycamore, giant hogweed, giant knotweed, and red valerian compete with native alders, willows and other trees shrubs and herbs. All attract insects, mostly but not all, native, and under their canopies, otter and mink interact and probably eat both native and exotic signal crayfish with equal relish. Native water vole and alien brown rat compete, probably aggressively and with the rat, a born survivor, winning out. This is a process I have dubbed ‘ecological fusion’ as a new, exciting and often vibrant ‘hybrid ecosystem’ emerges, a ‘recombinant ecology’. Make no mistake though, these systems are novel but also they will be here to stay and they will continue to evolve. The alien species can cause huge ecological, financial and even social problems, but we must learn to live with them and to manage the negative impacts more effectively. Many of these exotic or alien species, particularly some of the plants, are what we have called ‘ecological thugs’ and they can have major impacts on the natives. I will come back to this theme later with, I hope, some more surprising information. Nevertheless, for now just think about the fact that what we judge to be native or alien, acceptable and welcome, or unacceptable and unwelcome, is very subjective. Sweet cicely spreads aggressively along watercourses and highways but is a kind of honorary native. The beautiful leopard’s bane or the pretty Mimulus are both welcomed along riversides. Buddleia is a national treasure – the butterfly bush, yet does millions of pounds of damage to buildings and infrastructure. Even the supposed native rosebay willowherb is a probably a giant hybrid of North American and British variants of the original species, and is of course the food-plant of the wonderfully stunning large elephant hawkmoth.
Recent book on alien species
Anyhow, the riverside alien plants are not all bad news, because, in Sheffield for example, under the cover of city centre knotweed stands, native otter has re-established and we think may see off the invasive American mink. As one football commentator used to say, ‘…..it’s a funny old world….‘! And one where for now anyway, the grey heron is king.
Sheffield riverbank swamped by Japanese knotweed
Ian Rotherham, Writer, Broadcaster, Professor of Environmental Geography, Reader in Tourism & Environmental Change