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

Landscape (UK) - - Contents - Words: Di War­dle

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.”

Tree canopy

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.

Reach­ing out

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.

Ephemera dan­ica,

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.

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