Endangered mountain trees make a comeback in Scotland

Montane scrub provides protection from flooding, avalanches, rockfalls and landslides and supports a range of rare insects and scarce birds.

Overgrazing by deer and sheep on Scotland’s peaks since the 18th century contributed to a rapid decline in high-altitude woodland. By the 1990s, native montane willows were nearly extinct, with the largest remaining patch equivalent to the size of a tennis court.

Since then, almost 400,000 montane willows have been planted within 2,659 hectares managed for the restoration of mountain woodlands across Scotland, bringing the trees back from the brink of extinction.

The area these special arctic-alpine plants occupy has increased 100-fold since the 1990s thanks to the efforts of conservation charities and private estates working on a long-term vision for nature recovery.

PhD researcher Sarah Watts of the University of Stirling’s Faculty of Natural Sciences has reviewed progress made over the last 30 years.

Sarah said: ’There is significant capacity for a high-altitude vegetation type that was nearly nationally extinct to make a comeback and flourish under conservation management.

’Reviving a mountain woodland mosaic shaped by regeneration will tackle biodiversity loss and help mitigate climate change impacts on a national scale.

’Montane scrub supports a vibrant community of insects, including bumblebees, butterflies, moths, and over 20 rare sawfly species in Scotland that each rely on an individual species of arctic-alpine willow for their survival. The habitat also hosts upland birds that are scarce or declining elsewhere in Britain, such as the Ring Ouzel, a charismatic mountain blackbird.

’Mountain woodland also stabilises steep slopes and protects them from the natural hazards of avalanches, rockfalls, and landslides. It slows water flow over and within upland soils, facilitating a decrease in flooding downstream. These benefits are called nature-based solutions because they are vitally important for reducing threats from escalating climate change, including more extreme weather.’

Sarah is Chair of the Mountain Woodland Action Group and has been working on montane willow scrub restoration since 2010, first as a volunteer with the Trust, then as an ecologist at Ben Lawers National Nature Reserve from 2013 until 2020.

She began her PhD at the University of Stirling in 2019, and her previously published research mapped trees growing at the highest heights in Scotland. During her work to find scarce trees atop Scotland’s highest peaks, Sarah has bagged more than 200 Munros. In a paper published in 2022, Sarah also set out the benefits of mountain woodland restoration.

Her latest paper, Montane willow scrub restoration in Scotland: reviewing 30 years of progress to re-establish the altitudinal treeline was published in Restoration Ecology, the journal of the Society for Ecological Restoration.

The review looks at best practices across Scotland, featuring conservation efforts by environmental organisations, including Trees for Life, Cairngorms Connect, RSPB, Borders Forest Trust, Corrour, Forestry and Land Scotland, and particularly the work led by the Trust.

Sarah said: ’The pioneering site for montane willow restoration in Scotland is Ben Lawers National Nature Reserve, owned and managed by the National Trust for Scotland. No other restoration project in the country is comparable in scale and longevity.

’Here, widespread planting of 54,882 montane willows took place during 1998-2012. Over 110 hectares of montane scrub has now been restored at Ben Lawers, accompanied by an explosion of invertebrates, mammals, and birdlife. This site is undoubtedly the most biodiverse place in Scotland’s mountains.

Mar Lodge Estate, also owned and managed by the Trust, has demonstrated outstanding success in applying supplementary planting together with landscape-scale deer management; 5,797 montane willows planted here in 2021 and 2022 had a 100% survival rate during recent monitoring.

’These projects have inspired many others across the country and the careers of more practitioners and researchers such as myself. The review celebrates the vast contribution of the Trust’s staff and volunteers over decades to produce a thriving, vibrant altitudinal treeline with benefits to people and wildlife.’

Montane willow scrub is one of six habitats the Trust has prioritised in our Plan for Nature, announced earlier this year. As a conservation charity that cares for 76,000 hectares of countryside in Scotland from coastlines and islands to mountains, we use the plan to make clear where we will focus our efforts to help nature flourish.

Jeff continued: ’As Sarah highlights in her research, we have spent many years carrying out pioneering work to regenerate and restore this habitat at both Ben Lawers National Nature Reserve and Mar Lodge Estate National Nature Reserve. Nature needs to be protected now more than ever and our success so far in restoring montane willow scrub demonstrates what is possible when habitats or species are prioritised and given the opportunity to thrive.’