Harmony on the riverbank
As new life abounds, the creatures and plants at the water’s edge of the Wye in Derbyshire are thriving and supporting one another
Sunlight sparkles on the gentle ripples of the River Wye as it winds its way through the tiny Derbyshire village of Ashford-in-the-Water. The water is clear and shallow; trout visible among the low arches of the medieval Sheepwash Bridge as they search for flies among the weeds. Mallards nestle on the grass, beaks tucked deep into their feathers, and swans glide beneath the graceful willow trees that arch over the water. The Wye starts life among the wind-scoured rocks and heather of Axe Edge Moor, near Buxton. As it descends eastwards and the terrain flattens and fields open, it begins to broaden and slow, skirting ancient woodland and navigating the fishponds and weirs of former mills, before flowing into Ashford village itself. Its journey has taken it through the limestone valleys and gorges of the White Peak, and its still-cool waters are chalky and alkaline. All these factors influence the animals and plants living along its banks.
On the edge
“The riverbank is a really important environment,” says Dr Jeremy Biggs, of the Freshwater Habitats Trust. “It’s naturally dynamic and provides lots of opportunities for wildlife. ‘Edge’ habitats, such as the outskirts of woods or borders of meadows, are always more diverse than that ‘pure’ something: the wood or meadow itself. The riparian zone, as the area along the edge of a river is called, is an interface for lots of different fauna and flora.” The riverbank is shaped by the geology of the land through which a river flows. “If the ground is made up of cohesive soil, such as clay, the riverbanks will be steeper, but more gentle if made up of sandy material, which doesn’t so easily make vertical cliffs,” explains Jeremy. “The flow of the water also affects bank shape. In general, shallow banks form on the inside of a meandering river curve, where the slower flow means sediments are deposited, and steeper banks on the outside, where more erosion occurs.”
The waterside shrubs and trees that grow along the river’s edge are vitally important for the health of the riverbank. Although erosion is a natural process, a means by which rivers move sediment along their length in order to grow and change, bare riverbanks are in danger of collapse. Thick vegetation and trees cushion the bank, and their roots form a dense network which binds the soil together. Among the most familiar trees at the water’s edge is the alder, which can reach a height of 60ft (18m) or more in waterlogged soils around rivers, ponds and marshes. Lines of alder sometimes mark the original path of a river which has changed course. Willow trees are another common sight; the native white willow and crack willow also thriving in wet ground. The catkins produced by these trees are a source of nectar for bees and moths, and their leaves food for beetles, wasps and countless other insects. In autumn, the seeds are eaten by siskin and redpoll, and those that fall into the water by mallards and teal. The tree canopy shades the river; dappled light lowering the water temperature and helping to maintain oxygen levels. The long leaves and drooping branches of the ornamental weeping willow create an ideal hiding place for trout and other fish to escape predators, and leaves and twigs falling into the water are a further source of nutrients.
Many parts of the riverbank are lined with emergent vegetation: plants such as reeds, bulrushes and other sedges rooted in the shallows. The bright flowers of water-loving plants, such as bur marigold, ragged robin and common water crowfoot, create dashes of colour in spring, attracting butterflies, hoverflies and other pollinators. Several nationally threatened or locally scarce species are found along the river in Ashford, including Jacob’s ladder, mossy saxifrage, wood club-rush and pale willowherb. “Although the water is slower near the bank, it can sometimes be turbulent, with eddies sending flow patterns into reverse and the water having to move round these marginal plants,” says Jeremy. “This aside, you often find plants and animals that can live either in ponds or at the river’s edge which are happy as long as the water is not moving too quickly. These include the common water slater, a relative of the garden woodlouse, and the wandering snail, as well as plants such as watermint and brooklime. Small insects, including water crickets, also live among these plants, as a base to hunt tiny invertebrates trapped in the surface film of the water.” Marginal plants are a further buffer against erosion as well as providing food and nesting sites for birds such as the moorhen, often seen sheltering among the reeds with its young. They also oxygenate and purify the water, filtering run-off from surrounding fields. Marginal plants are particularly important as a link between the worlds above and below the waterline; vital for the many aquatic insects, such as damselflies and dragonflies, which spend their juvenile stages underwater as a nymph, but emerge to live their adult lives in the air. Nowhere is this phenomenon more dramatic than with the green drake mayfly, Ephemera danica. The larvae use their strong legs and tusk-like jaws to dig a tunnel in the gravel or silt of the riverbed, where they stay for between one and three years. When growth is complete, they move to shallower water, undergoing a moult to complete their transformation into a winged adult. Ascending to the surface, they shelter among the vegetation to shed their skin once more, before amassing in huge swarms over the water to mate. Females descend periodically to lay their eggs, dabbing their abdomens on the surface of the water, before both they and the males die, usually in a matter of hours. Flying insects, such as mayflies and moths, are food for the
brown long-eared bat and common pipistrelle that roost in old mill buildings along the river. They emerge up to an hour after sunset and often trace the path of the water or other linear features, like hedgerows, to hunt in the dying light.
Below the water
Life under the water is more unpredictable and changeable, as animals and plants have to contend with currents and a higher amount of sediment which is washed away from the bank. Submerged plants have strong roots to prevent them being swept away, but flexible, loose stems so that they do not rise above the waterline. Small fish, such as the three-spined stickleback, build their nests among weed in the shallows near the riverbank. Relatively weak swimmers, they rarely venture into the faster water towards the centre, where they may fall prey to bigger fish, such as trout, which prefer these oxygen-rich conditions. The Wye at Ashford is home to both brown and rainbow trout, as well as their close relative, the grayling. These fish thrive in the cool, nutrient-filled waters, spawning on the gravel and stones of the riverbed. Their fry shelter in the calmer waters near the bank, before moving back to the livelier waters as they get older. The river teems with a host of invertebrates, including snails, leeches and beetles, and especially the larvae of aquatic insects. They feed on algae and organic debris, and, in the case of carnivorous species, one another. Caddisfly larvae use silk produced in glands on the head to spin a protective
“Till a wind or water wrinkle, Dipping marten, plumping trout, Spreads in a twinkle And blots all out” Robert Louis Stevenson, ‘Looking-glass River’
case around themselves, which they reinforce with twigs, sand or other material. Some species stay in one place, filtering food from the water, while others take their cases with them as they move around the riverbed; head and front legs protruding from the opening at the front. Britain’s largest freshwater crustacean, the white-clawed crayfish, thrives in alkaline waters, including the Wye, using calcium to build its shell. These omnivorous animals forage for food in shallow, stony water at dawn and dusk, establishing territories among the weeds, which they defend aggressively. Once common at Ashford, they are now under threat due to the introduction of the North American signal crayfish, a non-native species which competes for food and space, as well as carrying a potentially fatal fungal disease.
Out and about
With its abundance of insects, fish and crustaceans, the river is a magnet for birds such as the kingfisher which swoops over low, quiet water to hunt and burrow into the bank to nest. Dippers are among those that prefer faster flowing parts of the river. “They can often be spotted standing on stones in the water, and they seem to have favourite stones that they return to again and again,” says Jeremy. “It’s worth looking out for them, bobbing up and down before they jump into the water to hunt.” Dippers walk along the riverbed in search of food, using their long claws for grip; wings outstretched to counteract the current and keep them submerged. From April, the high-pitched song of the grey wagtail can be heard as it moves to the waterside to breed, feasting on midges, snails and beetles. The bright yellow breast of the male is easily spotted as they perch on rocks, their long tails constantly moving up and down. Nests are built in hollows or in the nooks and crannies among stones near the water and are lined with moss and twigs. The timid otter builds extensive holts among the straggling roots of trees such as the alder; underwater entrances allowing them to slip in and out of the river unnoticed. Although it spends much of its time on land, its streamlined shape and thick fur mean it is equally at home in the water, searching for fish, frogs and even small birds. Its large lungs allow it to submerge for up to four minutes at a time, ears and nostrils sealed by special valves. A male otter may guard a territory as long as 12 miles along the riverbank. Water voles have suffered a huge decline in numbers, but some of the largest remaining populations live on the Wye. These glossy, rat-like animals build networks of tunnels in the bank, with at least one entrance below the waterline.
“A ramble by the rivers side In Spring times dewy eve Where teal and widgeon turn to hide In reeds which them receive” John Clare, ‘A Ramble by the River Side’
Some of those above may include an ingenious U-bend so that the tunnel fills with water, protecting the vole from predators such as stoats and weasels. Water voles do not stray far from their burrows and spend relatively little time in the water, as they do not have webbed feet and cannot swim for long. A sure sign of their presence is a pile of nibbled grass around an opening on the riverbank.
Protecting the river
“It’s important to keep our rivers as natural as possible, which means allowing trees to grow alongside them and gentle grazing on the banks by large animals, such as cattle. Grazing and trampling of river margins has gone on for millennia,” says Jeremy. He believes that people should look out for their local streams, rivers and ponds, and encourage landowners to keep the land around them as non-intensive as they can, as this is the best protection for the water. “Rivers are among our richest freshwater habitats, and they are important corridors for wildlife.” The Wye continues on its journey, broadening on the way to Bakewell before it flows past the medieval grandeur of Haddon Hall. Then it is on to the village of Rowsley, where it will finally merge with the larger River Derwent.
Dr Jeremy Biggs is director of the Freshwater Habitats Trust, https://freshwaterhabitats.org.uk, and runs the Clean Water for Wildlife project. Sightings of protected species at Ashford can be reported to the Derbyshire Biological Records Centre, www.derbyshirewildlifetrust.org.uk.
Bulrushes, Typha latifolia, are always found near water, including flooded areas (above). Common water crowfoot, with its buttercup-like flowers, can form mats on the water (below).
Elusive Jacob’s ladder, Polemonium caeruleum, in bloom (left). The starry white flowers of Saxifraga hypnoides, found in damp soil, appear from May in the Peak District National Park (right).
A green drake mayfly, newly emerged on a riverside grass stem. It has large, dark-veined hind wings and three tails (left). A recently hatched dragonfly, its wings almost transparent, next to the shell of the nymph (right).
Brown trout fry emerge from the gravel where they were hatched and move towards the light to feed on tiny insects in the water.
The grey wagtail, with its bright yellow underside, is usually found by rivers or streams in the warmer seasons. A white-clawed crayfish, Austropotamobius pallipes, the only species of crayfish native to the British Isles.
Water voles often sit in one place to eat, leaving behind a small pile of stems.
A dabbling male mallard, with its glossy green head, by the edge of the River Wye in Rowsley.
An otter keeps watch along the riverbank as it dips in and out of the water.