The Scots pine plantations in Abernethy forest are the crème de la crème in forestry terms: tall, straight and dense. These plantations were created in the 1930s, and the wood had a variety of uses, from ships’ masts to trench timbers. Now, this woodland is being retrofitted for wildlife as part of the UK’s largest land restoration project because, although it is striking to wander in such a regimented landscape, nature prefers things to be less orderly.

The gnarled older and bigger trees are better for woodland species, which is why conservationists working on Cairngorms Connect are intentionally making a mess and artificially ageing trees as part of their efforts to restore Scotland’s old Caledonian pine forest to its former, imperfect glory.

Over the total area of the Cairngorms Connect project – 600 sq km (230 sq miles) – partners are spending more than £40,000 a year on plantation restructuring, which includes a range of wildlife-enhancing projects, from artificially ageing trees to thinning out commercial plantations. More than 10 sq km of Scots pine has been restructured since 2019. “Here we want twisted, forked trunks, we want the more open-crowned trees,” says Jeremy Roberts, programme manager at Cairngorms Connect, who is showing me around. The woodland is draped in spiderweb lace and the spongy forest floor is spattered in blaeberry, also known as bilberry.

Large natural forests are affected by storms or have grazing animals moving through them, knocking down trees and creating “storm tracts”, so conservationists are replicating this process by using a winch and ropes to pull the trees down. They are also doing ring barring, which means scraping off a circle of bark a few metres up the trunk. It looks as if a hungry giant beaver has chomped its way through the forest. A tree surgeon even cut the top off one of the trees and now the deadwood is being used by a woodpecker.

These homogenous forests have less than 15% of the deadwood that should be there. It might seem odd for conservationists to intentionally damage trees, but dead and decaying wood is a crucial habitat. These pinewoods are the most important sites in Scotland for deadwood-loving beetles. Conservationists have recorded 144 species of saproxylic beetle, 32 of which are of conservation concern.

Getting light into the woodland floor also helps to establish broadleaf trees such as birch, rowan and juniper, which can’t survive in dense forest. “A goldilocks amount of light is always useful in a Scots pine plantation. A bit too much light and you end up with a dominance of heather, a bit too little light, and you end up with a dominance of grass,” says Roberts.

Cairngorms Connect land is home to 55% of the UK’s capercaillie population and 90% of them are in Abernethy forest. As ground-nesting birds, the tangle of logs provides shelter and cover for them. The exposed roots provide the dust capercaillie need to keep their feathers in good condition and get rid of parasites. “The single most useful thing is expanding the forest, making more forest habitat for capercaillie, and that can happen surprisingly quickly if you control the deer numbers,” says Roberts.

Currently, the project has 130 sq km of forest. The aim is to double that as part of the 200-year vision, mainly through natural regeneration, rather than mass planting. Young woodlands are flowing out into the moorland like a river and there is a single key reason for this: culling deer.

In the early 2000s, there were more than 25 deer a square kilometre; now there are just one or two. Numbers have been so successfully reduced because all landowners included in the project agreed to do it over a vast area.

The Cairngorms Connect project has £9m of funding, including about £3.7m from the Endangered Landscapes Programme. Landowners involved in the project include RSPB, Forestry and Land Scotland, NatureScot and Wildland, set up by Danish billionaire Anders Holch Povlsen. This landscape has been damaged over centuries and the vision is to “rewiggle” rivers, rewet peatlands and restore forests.

Unlike other conservation projects, Cairngorms Connect covers a vast area of continuous land owned by a handful of landowners. Forestry and Land Scotland has owned Glenmore for nearly 100 years, RSPB has worked at Abernethy for 60 years, NatureScot has been at Invereshie for 60 years and Povlsen bought Glenfeshie in 2006.

Four senior representatives from each organisation have met with the Cairngorms national park authority almost every month since 2014. If the key person can’t make a meeting they’re not allowed to send a proxy. “It’s a tight group of people with a lot of trust, which makes it a safe space to challenge and that’s where great collaborative ideas come from,” says Roberts.

The project had a low-key launch in 2016 because a lot of work was already happening in the respective areas, but things such as deer management work more effectively over a wide area. If you cut deer numbers, creating new forests in places you have existing forests is pretty easy. Seeds from pine forests can be dispersed 150 metres away from the parent plant over moorland and if the density of deer is below four per square kilometre then the pine will regenerate.

A report from 2020 estimated that there were up to 1 million wild deer in Scotland, which could be seriously hampering national efforts to increase tree cover. “The priority here is expanding the forests. All the partners are achieving forest expansion by deer control,” says Roberts.

We walk into the open area leading to Ryvoan bothy, where saplings are sprouting. On one side of the path a forest of rowan is forming from seeds planted by wintering thrushes, such as fieldfares and redwings, says Roberts. They feed on berries, then go into the heather to roost, dropping seeds as they go, which grow into saplings.

Next morning, I wake at 5am to do the wildlife equivalent of financial accounting, to see what impact these investments are having on species diversity. Ellie Dimambro-Denson, a monitoring officer at Cairngorms Connect, is doing a high-altitude moth survey up the hill from Glenmore visitor centre, using a Robinson light trap. We are joined by what feels like a million midges.

These traps are set once a month between May and September at a variety of altitudes – the lowest is at 300 metres and the highest at 900 metres. Moths are great indicator species because they are diverse and respond quickly to changes in the landscape.

“We can get so much data in one session,” says Dimambro-Denson. “Moths have relatively fast reproductive cycles and so are able to colonise areas quickly and respond to habitat changes, especially sudden change such as tree planting and other direct management work, on short timescales.” She counts 469 moths from 39 species (plus an additional 46 micro-moths) – including a nationally scarce angle-barred sallow – which is a relatively large and diverse haul. It also includes a brimstone moth, whose caterpillars feed on blackthorn, hawthorn and rowan, and a green carpet moth, whose caterpillars feed on oak and rowan. Their presence suggests broadleaf regeneration is working. “You can see a response. That’s very exciting,” says Dimambro-Denson.

Regular moth trappings can show which direction the landscape is moving in. What Dimambro-Denson has done this evening is repeated each year so conservationists can understand how the landscape is changing. Similar monitoring surveys are being done with birds and vegetation. “You could come back in five, 10 or 100 years and repeat this,” she says.

The landscape is becoming a complex mosaic of habitats, but the basic ingredients are simple: reducing deer and giving the landscape time and space to recover. Although this is not being billed as a rewilding project, nature is at the helm and the land is naturally covering itself in a complex of forests, bogs and wild rivers.

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