Wild­flower won­der­land

The ge­ol­ogy of a cer­tain area of County Durham has cre­ated a unique habi­tat that pro­motes an en­vi­ably high bio­di­ver­sity – the mag­ne­sian lime­stone grass­lands.

BBC Wildlife Magazine - - Mag­ne­sian Lime­stone Grass­lands - SHEENA HAR­VEY has just re­tired as ed­i­tor of BBC Wildlife. Her visit to the Durham grass­lands was hosted by Visit County Durham: thi­sis­durham.com

Climb­ing over a stile into Lit­tle­wood Lo­cal Na­ture Reserve, in the heart of County Durham, I find the first field knee-high in rough meadow and sweet ver­nal grasses, meadow fes­cue and cock’s-foot, and wild­flow­ers: wound­wort, bird’s-foot tre­foil, knap­weed, speed­well, herb robert, hoary plan­tain, red and white clover – a botan­i­cal smör­gas­bord.

A lot of time and trou­ble has gone into re­mov­ing the rich rem­nants of agri­cul­tural pro­duc­tion from this small, mixed patch – bounded by a main road and the scars of three large quar­ries – to restore a habi­tat in which wild­flow­ers and all their as­so­ci­ated in­ver­te­brates and birds flour­ish.

It’s June and the myr­iad shapes of the grasses and the bril­liant nat­u­ral colours are daz­zling. Fur­ther as­sault­ing the senses, there’s the smell of fresh herbage warm­ing in the sun, the danc­ing move­ment of but­ter­flies, the buzz of bees, and the rapid chip-chip of a lin­net from the hawthorn sur­round­ing the meadow.

“The hawthorn is good for bird life,” says Adam Dixon, coun­try­side ranger for Durham County Coun­cil, who over­sees the reserve. “But it en­croaches on the grass­land, so we have to keep it in check.” The same

goes for rose­bay wil­lowherb, which he takes the tops off as we en­counter the plants on our walk. This will help to pre­vent the flow­ers set­ting seed and spread­ing, he says. This hugely suc­cess­ful plant was given the nick­name of fire­weed be­cause of the speed it colonised bomb sites in World War II. Given the chance, it would en­gulf the more del­i­cate species in the grass­land, so it can­not be left alone.

The good, the bad and the ugly

Volunteers help with clear­ing wil­lowherb and the courser grasses through the grow­ing sea­son and cat­tle graze in the win­ter months to churn up the ground and keep down the less de­sir­able veg­e­ta­tion.

“We oc­ca­sion­ally spread yel­low rat­tle seeds, to help sup­press the ranker grasses,” says Adam. “Yel­low rat­tle par­a­sitises those grasses, which kills them and opens up the grass­lands to al­low wild­flow­ers to flour­ish.” A par­tic­u­lar prob­lem in the Durham area has been up­right brome, a grass that has been steadily spread­ing north­wards from its south­ern and mid­dle Eng­land heart­land. If this takes hold, it can dom­i­nate a meadow; its dense tus­socks and leaf lit­ter in­hibit­ing more del­i­cate plants from tak­ing root, thus sti­fling bio­di­ver­sity. Reg­u­lar mow­ing and graz­ing is nec­es­sary to keep this in­vader from tak­ing over.

The meadow was arable farm­land un­til 2005 when Durham County Coun­cil took it over. It sits over the site of East Het­ton Col­liery that closed in the early 1980s, and of which lit­tle ev­i­dence re­mains, apart from the cov­ered-over spoil heap, now criss­crossed by tracks and planted with conifer wood­land for com­mer­cial use. The only

other sign that this was once a thriv­ing coal mine, em­ploy­ing about 1,500 men at its height in 1896, is the oc­ca­sional con­crete drainage con­duit that runs through the site.

Unique ge­ol­ogy

The ter­rain in the area has been shaped by its unique ge­o­log­i­cal com­po­si­tion. This part of cen­tral County Durham, from as far west as Bishop Auck­land in the south and Houghton-le-Spring in the north, and stretching to the east coast be­tween South Shields and Hartle­pool, is a roughly tri­an­gu­lar mag­ne­sian lime­stone plateau. Mag­ne­sian lime­stone is one of a group of dolomite lime­stones that run in a line, be­tween 2–8km wide and about 200km long, from Not­ting­ham to Sun­der­land.

This lime­stone is unique in the UK and dates back to the late Per­mian Age, 240 to 270 mil­lion years ago, when the area was cov­ered in a large, land-locked stretch of fresh water called the Zech­stein Sea. This was a time be­fore the world’s con­ti­nents had drifted apart and the Zech­stein was bounded by nar­row strips of land out­side of which was a much larger saline sea. The strips of land were con­stantly breached by in­cur­sions from the outer sea, in­tro­duc­ing salt to the fresh water that grad­u­ally ac­cu­mu­lated to make the water hy­per­saline, in the way the Dead Sea has formed to­day.

Through time, and with a chang­ing cli­mate, the water evap­o­rated and min­er­al­rich de­posits formed the lime­stone lay­ers, over­lay­ing sand and the seams of gas and coal that sus­tained the lives of Durham and York­shire min­ers for gen­er­a­tions. Nowa­days, the collieries are gone, though the lime­stone is still quar­ried for ag­gre­gates.

In 2007, it was recog­nised that the mag­ne­sian lime­stone pro­moted a type of grass­land with a huge diversity of flora and fauna, and that it should be safe­guarded. The Lime­stone Land­scapes Part­ner­ship was formed be­tween Durham County Coun­cil, Nat­u­ral Eng­land, His­toric Eng­land and a raft of lo­cal coun­cils, wildlife and out­door or­gan­i­sa­tions. It op­er­ated be­tween 2007 and 2016 to pro­mote and pre­serve the nat­u­ral re­sources of the area, a le­gacy that con­tin­ues. Its work in­cluded re­turn­ing sites such as Lit­tle­wood Lo­cal Na­ture Reserve to the bio­di­verse rich­ness that ex­isted be­fore mod­ern agri­cul­ture made use of the land.

The her­itage of decades of farm­ing at Lit­tle­wood had left the ground full of fer­tiliser and pes­ti­cides and it has re­quired care­ful man­age­ment to re­turn it to a na­tive meadow pro­vid­ing habi­tat for a range of an­i­mals, including ground-nest­ing birds, such as grey par­tridge.

Land man­age­ment

“Cat­tle, par­tic­u­larly High­land cat­tle, and Ex­moor ponies are the pre­ferred species to graze the meadow be­tween Oc­to­ber and April,” says Adam. “They are less picky than other graz­ers in their habits. High­lands will clat­ter through ev­ery­thing, even gorse!

“Two years with­out graz­ing and you lose the sward height, the rank stuff takes over and you have lost the bio­di­ver­sity. As it is, this Site of Spe­cial Sci­en­tific In­ter­est meadow is be­tween two oth­ers and is part of a scheme to build up a wildlife cor­ri­dor all the way to the coastal grass­land sites.”

The man­age­ment of the land is high­lighted in the sec­ond field be­yond a thick hawthorn hedge. This meadow is in a nar­row val­ley, with the hedge on one side and mixed de­cid­u­ous trees and bushes on the other. “We leave at least 10 per cent of this meadow un­cut, on ro­ta­tion,” says Adam, “in or­der to pro­vide shelter for smaller mam­mals and am­phib­ians.”

He points out how the wild­flow­ers and grasses grow well in most of the field, but in the bot­tom quar­ter net­tles and rose­bay wil­lowherb grow to waist height and to the ex­clu­sion of the more del­i­cate grasses. “We hand mow the meadow,” he says. “But the way in is too nar­row to get in a trailer big enough to re­move the cut­tings in any quan­tity. So we’re forced to dump them at the bot­tom of the field. The cut­tings rot down, but they leave the soil nu­tri­ent-rich, which is great for net­tles but not the kind of plants we want, that thrive on nu­tri­ent-poor ground.”

The wild­flower mead­ows are one as­pect of the re­gen­er­a­tion of the reserve. The sec­ond is the area where Adam is ex­per­i­ment­ing with scrap­ing off the farmed ground, leav­ing rocky yel­low mag­ne­sian lime­stone only thinly cov­ered in soil. “The south­west-fac­ing land is shel­tered,” he says. “This brings the heat in and we have in­tro­duced com­mon rock-rose and var­i­ous other na­tive species as plug plants. We’re look­ing for that bal­ance that will cre­ate a mo­saic of habi­tats that are good for a wide range of species.”

In terms of in­ver­te­brate life, he adds: “The 5–10cm height of the sward on this patch is good for the north­ern brown ar­gus but­ter­fly, a na­tion­ally rare species known lo­cally as the Durham ar­gus, that lays its eggs on the com­mon rock-rose, which pro­vides food for its cater­pil­lars. Even lower growth suits the dingy skip­per but­ter­fly.”

Al­to­gether, this small reserve hosts more than 18 species of but­ter­fly, bur­net and chalk car­pet moths, at least four species of bum­ble­bee and many other in­ver­te­brates. Bird life in­cludes sky­larks, wil­low tits, lit­tle owls and grey par­tridge, the lat­ter thriv­ing here in con­trast to na­tional de­clines. The mam­mal pop­u­la­tion fea­tures brown hares, field voles, weasels and, less hap­pily, rab­bits.

Rab­bit ver­sus orchid

One of the reserve’s pride-and-joys is the dark-red helle­borine, a rare wild orchid found in only a few ar­eas of Bri­tain. The limey nu­tri­ent-poor scrapes at Lit­tle­wood suit the flower, but sadly the flower very much suits the rab­bits, as a de­li­cious nib­ble. Adam ad­mits that it’s some­times a war of at­tri­tion to pro­tect the helle­borines from an over­pop­u­la­tion of rab­bits.

The rock-roses that are now grow­ing ex­ten­sively on the newer ex­posed lime­stone ar­eas were spread from seed taken from ar­eas of the site where they oc­cur nat­u­rally. One of these places is be­side the con­crete

Mag­ne­sian lime­stone pro­motes a type of grass­land with a huge diversity of flora and fauna.

cul­verts that took water round the spoil heap to the mine, which did not see the soil en­riched like the site’s agri­cul­tural sec­tions.

An­other rare ground-hug­ging plant, the basil thyme, also thrived near the cul­verts, ben­e­fit­ting from the lime-rich en­vi­ron­ment and lack of her­bi­cides. Lit­tle­wood is one of only four colonies of basil thyme that still ex­ist in County Durham. Classed as Vul­ner­a­ble, this mem­ber of the dead-net­tle fam­ily is listed as a plant “of prin­ci­ple importance for the pur­pose of con­serv­ing bio­di­ver­sity” in the 2006 Nat­u­ral En­vi­ron­ment and Ru­ral Com­mu­ni­ties Act.

Lit­tle­wood en­cap­su­lates the beauty and bio­di­ver­sity of Durham’s mag­ne­sian lime­stone grass­lands – pre­cious habi­tats clawed back from in­dus­tri­al­i­sa­tion and in­ten­sive agri­cul­ture to show­case what can be achieved with care­ful man­age­ment. A net­work of sites that in­cludes Thris­ling­ton Plan­ta­tion Na­tional Na­ture Reserve (NNR), Cas­tle Eden Dene NNR, Cas­sop Vale NNR and Black­hall Rocks, among oth­ers, of­fers a step back in time and a step for­ward into the fu­ture for our na­tive wildlife.

Clockwise from above: rock-rose, on which north­ern brown ar­gus but­ter­flies lay their eggs; Adam Dixon, show­ing the vary­ing sward heights at Lit­tle­wood; East Het­ton col­liery and slag heap in 1983; the rocky nu­tri­ent­poor land­scape suits flower-rich grass­lands; a bur­net moth feed­ing on knap­weed.

Above: wild or­chids thrive at Thris­ling­ton. Be­low: net­tles in­di­cate nu­tri­ent­filled soil that in­hibits bio­di­ver­sity.

A wide range of na­tive plants are good for in­ver­te­brates and birds such as sky­larks.

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