The Eastern Moors are a beloved northern treasure – but are they also an unlikely threat to the climate?

They call the Eastern Moors the gateway to the Peak District. There could hardly be a more apt description. The residents of Totley, a village now absorbed within Sheffield's sprawling outskirts, can literally open their garden gates and step onto the drystone-walled pastures that rise to the blustery, heather-clad heights of Totley Moor.

"Between where the houses end and the heather starts is just four fields," says Danny Udall, site manager of the Eastern Moors Partnership, a new collaboration between the National Trust and the RSPB which, this spring, took on the lease of the 27sq km area west of Sheffield from the Peak District National Park Authority.

As he speaks, as if to assert the presence of wilderness on the doorstep of the metropolis, two buzzards circle overhead and a curlew skims across a meadow, its liquid call carrying plaintively over the moor.

From the top of Totley Moor, you look back to the tower blocks of Sheffield, but a few moments on, big views open out on sweeping valleys, the angular outcrop of Stannard Edge and Kinder Scout glowering on the horizon.

This is emotive country, inked indelibly into folk memory with the rights of free countryside access after the mass trespass against the local grouse shooting estate owners in 1932.

The Peak District was the first area in Britain to be designated a National Park in the more consensual post-war period, but before that it was the Eastern Moors which had played an early role in affording the working classes from the nearby areas of Sheffield, Chesterfield and Manchester the opportunity to roam. "Some of the earliest informal agreements between various rambling clubs and gamekeepers to allow at least limited access were in the Eastern Moors," says Udall. "The pressure built as a result of this, leading on to the famous 'trespass' on Kinder Scout." While the Eastern Moors are essentially part of the same gritstone geological landscape – known as the Dark Peak – as Kinder Scout, there's a sense in which they are also the reassuring "hills of home" for locals, more intimate, wooded and accessible. As Udall puts it: "A lot of people walk or drive up out of Sheffield here for 10 minutes in the evening after a day in the office. The larger hills and higher moors of Kinder and Bleaklow are loved just as much, but it requires boots and rucksacks to get to them, so somehow the relationship with the Eastern Moors is closer."

It's this sense of belonging that the Partnership aims to tap into. This is the first time these two conservation giants, RSPB and the National Trust, have linked forces in this way. Their complementary experiences in cultural management, recreational access to moorland and science-led conservation and research convinced the National Park Authority, under pressure to optimise its resources, that they offered the best means of demonstrating, as Udall says, "how uplands can be managed for both people and wildlife".

Yet the Partnership's brief goes wider still. The National Trust has spoken of making the Eastern Moors "an open air laboratory where people can learn about the effects of climate change".

Udall describes the Moors' role as akin to that of a canary down an 18th century coal mine. "We are at the very base of the Pennines and it is anticipated that any changes resulting from global warming in the uplands will be seen here first. One of the key indicators of climate change is species range. Already we have had Dartford Warblers, a bird more usually associated with the heaths of southern England, up here and nightjars have been nesting in the area. It could be that we actually have to regard some parts of the Moors more like heathland in future." But while one aspect of their task will be habitat adaptation, mitigation is arguably an even greater challenge because of the area's vast peat reserves. Peat is a natural storer of carbon dioxide and it has been estimated that global peat reserves lock up twice the amount of carbon held in the entire hectarage of the world's forests.

But while peat only covers about 3 per cent of the Earth's surface, 15 per cent of it is in the United Kingdom – retaining the equivalent of over 20 years of the country's industrial carbon dioxide emissions.

The Peakland peat reserves are some of the most important, but the National Trust has already sounded alarm bells over their degraded condition – due to drainage, heather burning and centuries of overgrazing by sheep. When peat dries out it begins to leak carbon into the atmosphere so that, instead of being a mitigator, it actually adds to greenhouse gas effect.

While the Trust has already started peat restoration on its own High Peak Estate, the Partnership's work on the Eastern Moors will be just as critical. The Eastern Moors contain saddleback mires which are formed by the accumulation of decomposed vegetation in moist conditions over thousands of years, "hummocking up" to form saddlebacks. At around 6-7m, they're deeper than the blanket bogs found elsewhere in the Peak District.

Leash Fen is a classic example, though it's quite a forbidding spot to explore. "It would take you over half an hour to walk out into the middle and if you did it without falling into a wet hole you'd be very lucky," says Udall, as we stumble across the tussocky, purple moor grass to reach the wide, 200-year-old ditch that separates us from the treacherous-looking mire. "If you'd stood here centuries ago, you'd have been looking at a wooded river valley. The "saddleback" built up in the intervening years from the sphagnum mosses and rotting leaf matter," explains Udall. "But peat made these fields totally unproductive from an agricultural point of view. The ditches were laid to siphon the water off and dry the fields out, so they could be used for grazing or grouse shooting."

That may have brought the fields into use during times when the population pressures on the moors were higher than they are today. Udall recalls an old saying: "When Chesterfield was heath and down, Leash Fen was a market town", which may be apocryphal, but indicates the importance of the land to feed the locals. However, it also left a ticking time bomb in the form of leaking carbon. Research suggests that some 700m sq (7,500 ft sq) of the southern Pennine Hills now leak as much carbon dioxide as a town populated by 50,000 people.

Of the three mire systems on the Moors, Udall says Leash Fen is the largest, but the least intact. With sheep grazing now cut back drastically, work will begin this year to block the ditches, re-seed exposed peat with heather and sow cotton-grass, so that the mire begins to hold its moisture once more and effectively lock carbon in again, instead of leaking it into the atmosphere. It will be a lengthy process, but signs that it is working will lie in the re-emergence of rare acid bog-loving species such as the sphagnum mosses, sundew, bilberry and cowberry return – or, as Udall says, when viewed from Sheffield, the moors have turned from their current over-grazed yellow to the purple-brown of heather.

There is, of course, massive public cynicism right now about global warming, but Udall hopes that witnessing its effects on their beloved Moors might help people "make the link between what is happening on the ground with what is happening to our climate".

How fitting it would be if these peaty moors, so integral a century ago to forging the interconnectedness of urban northerners with nature, were to be the melting pot for forging a better understanding of the greatest environmental challenge of our times?

Three wonders of the Eastern Moors

Curbar Edge

"The classic Eastern Moors landscape with its rugged gritstone edges, but the view across the Hope Valley to the softer limestone escarpments of the White Peak gives you the two faces of the Peak District." Danny Udall, site manager, Eastern Moors Partnership

Ramsey Moor

"It's very secluded and you walk down into a valley with a stream and trees at the bottom. The intimate, enclosed atmosphere is totally different to Curbar, which can get quite busy." Kim Strawbridge, estate warden, Eastern Moors Partnership

Totley Moor

"From a cairn at the top you look down on Sheffield below you, with its high rise flats and office blocks, leading over towards Hillsborough. It's like looking at a map of the city, but you find yourself thinking I'd rather be up here." Andy Carson, estate warden, Eastern Moors Partnership