STEPHEN LEWIS visits a local nature reserve in the heart of York as is prepares to celebrate its tenth birthday in style.

FIGHT your way down through a tangle of undergrowth at the northern end of the St Nicholas Fields' nature reserve and you reach Tang Hall Beck, a narrow stream of mud-brown water flowing between heavy clay banks.

On the opposite side of the beck, cyclists are buzzing along the Sustrans cycle track towards Osbaldwick. Down here, however, it is quiet, the air heavy with humidity.

A bit further along, where the beck disappears into a culvert, is one of the best places in York to watch for kingfishers, says Jonathan Dent.

The beck is also home to most of St Nicks' resident population of water voles.

They're an endangered species – so St Nicks' is proud of them. "We're starting to get more and more every year as they move down the 'route 66' cycle path," says Jonathan, the St Nicks reserve manager.

Like most waterways in York, the beck is prone to flooding. "But it doesn't seem to put the water voles off," Jonathan says. "We spot them regularly."

There is no sign of the tiny, blunt-faced little mammals today. But peer closely and you can just see, almost hidden in the rich earth of the beck's opposite bank, a small hole, presumably a water vole's home.

What is perhaps most remarkable about this area of scrubland bordering the beck below the John Lally community woodland, however, are the reminders of St Nicks' past.

The 24 acres that now make up what staff and volunteers here like to call the 'green heart of York' was once a clay pit with associated brickworks. For a hundred years or so from the 1800s, a succession of pits were dug. By the 1950s, St Nicholas Fields was a landscape of pits, hollows and hummocks left by the brickworks.

Then the city council decided to use it as a rubbish tip. For 20 years, up until 1974, the huge holes where for years clay had been dug out of the ground were used to dump the city's domestic and industrial rubbish, everything from old tyres and leaking oil drums to waste from the Rowntree apple presses.

It is more than 20 years now since the former tip was capped with a thick layer of clay to seal in potentially toxic pollutants and converted into an urban nature park. And it is ten years since St Nicks was officially designated a Local Nature Reserve.

It is now a wonderful slice of nature just a mile from York's city centre: a mixture of native woodland, scrub and meadow that is home to more than 20 species of butterfly; countless other insects; birds such as black caps, wrens, finches, brambling, kingfishers and siskin; and wildflowers with bewitching names such as ragged robin, vetch, corncockle, creeping-jenny, goat's rue, purple loosestrife and meadowsweet.

Everywhere in the reserve, however, beneath nature's covering mantle, are signs of the area's past: humps and hollows; bits of old brick and stonework sticking out of the undergrowth; and, down by Tang Hall Beck, pieces of an old metal barrel emerging from the clay.

Jonathan doesn't know what it is, he admits. "There are still things here – stuff left over from its previous life. But the wildlife is working its way around it."

One of his favourite areas of the reserve is the old brickwork manager's house, he says. Rather than pull it down, it was simply left. Nature took over, and a thicket grew up around it. "It's now a wonderful wildlife haven."

If ever you needed reminding of the power of nature, this place is it. "That's our story," Jonathan says. "Nature winning out."

It has had a helping hand from the Friends of St Nicholas Fields, from the handful of paid St Nicks staff and from the hundreds of volunteers who help to look after this slice of urban nature.

In the past year alone, says Ivana Jakubkova, the St Nicks events officer, volunteers have put in 8,000 hours of work at the reserve. They do everything from coppicing to planting wildflowers, clearing litter, scything the hay meadows, and spreading rich compost to promote the growth of trees and flowers.

Volunteers with the reserve's 'wildwatch' group also come out for two hours every Wednesday to make a count of the bird, animal and plant species found here. Each year since 2011 they have published the St Nicholas Fields Wildlife Report: a detailed record which shows just how this wonderful reserve is thriving.

"With every passing year, the diversity of species species grows and the Wildwatch group have more to map and report," says Tom Waring, the chief officer of the Friends of St Nicholas Fields, in his introduction to the most recent report.

As anyone who loves this nature reserve knows, however, the best thing about it is that it is here to be enjoyed by everybody: from the most hardened nature watcher to the casual dog-walker and the family out for an afternoon stroll.

It is filled with quirky little corners, such as the Dragon Stones stone circle – put together from bits of stone dumped here, some of it thought to be from an old and now vanished church – to a children's play area and the butterfly walk, lined with buddleia.

And then there's the York Environment Centre itself, opened in 2000, where events for families and children cover everything from how to grow your own garden veg to how to make proper compost.

Families and children are also invited to regular planting events, helping to further increase the range of wildflowers and trees found here.

There is plenty to celebrate, then, now that the reserve has reached its tenth birthday. And on May 10 the Friends of St Nicholas Fields will be doing exactly that – holding a 'big green celebration' to mark ten years of the reserve.

It will be a "half day of free fun activities for all ages, including wildlife walks, green crafts demonstrations, children's activities, competitions, refreshments and lots more," says Ivana Jakubkova.

Above all, it will be a great chance to see for yourself what has been achieved by the efforts of a local community in turning an unloved landfill site into a slice of nature on their doorstep. Water voles and all.

All the way back to common land

The earliest mention of St Nicholas Fields was in the 12th century, when the land was leased to the nearby hospital of St Nicholas, a leper colony founded in the reign of King Henry I.

York Corporation records show that by 1597 the area had become common grazing land, where, according to a history of the site, “115 commoners grazed 88 cows and 41 horses.”

In 1837, St Nicholas Fields, together with surrounding land, was bought by James Barker for £10,000 and rented out for clay extraction and brick making. Brickmaking continued here for more than a hundred years, until the closure of the St Nicholas Brick Works – which made bricks for the Tang Hall estate – in the 1950s.

The area was then adopted by the city council as York’s rubbish tip and the flooded pits and hollows of the clay pits were gradually filled with York’s rubbish.

The ‘Tang Hall tip’, as it was known, closed in 1974, and within a few years nature was beginning to take over again, with flowers and shrubs and natural woodland creeping back. “Local people started to appreciate the unofficial green space on their doorstep,” the history of St Nicholas Fields reports.

It looked as though that brief flowering of nature might be short-lived. In 1988, a report in the Yorkshire Evening Press mentioned that the tip was to be developed by the city council as an industrial site. But the report also mentioned that a new environmental pressure group, the York Natural Environment Trust, would like to keep it in a ‘really wild state’.

A campaign was launched, coordinated by Gordon Campbell-Thomas – who was to go on to become a founder of the Friends of St Nicholas Fields and, for ten years, the St Nicks park ranger.

The campaign proved highly effective. In 1993, after the site had first been capped with a thick layer of clay to seal in any potentially toxic pollutants, St Nicks was designated an urban nature park.

The layer of clay meant that at first, the new park was a fairly bleak place. “Over much of the site, the few remaining trees and shrubs were isolated in a sea of sticky clay,” the history of St Nicks says. “The new paths were stark ribbons of tarmac snaking across this wasteland.”

The Friends of St Nicholas Fields got to work. With the support of volunteers, they planted several thousand trees and shrubs, sowed wildflower meadows, built new pathways, and cleared away tons of rubbish.

Nature also did its work, sprouting in such profusion that today the reserve is home to a wealth of birds, insects, wildflowers and other plants, as well as small mammals such as the water vole.

St Nicks was designated a Local Nature Reserve ten years ago. The reserve will be officially celebrating its tenth birthday on May 10 this year.