See all stories
14 Jul 2022

Rare arctic-alpine plants becoming endangered on Ben Lawers

A view from the green summit of a very high mountain, looking down towards lower ridges and a lochan. Cloud is rolling in over the hills in the distance.
View to Lochan nan Cat from Ben Lawers summit | Image credit: Sarah Watts
Rare arctic-alpine plants are being driven higher up our mountains by climate change and could soon become extinct in Scotland if we don’t intervene, detailed analysis of long-term monitoring data has confirmed.

Snow pearlwort, drooping saxifrage and mountain sandwort, which all enjoy a cool climate at high altitude, are retreating up the slopes of the Ben Lawers range in the Highlands.

The rate of decline of snow pearlwort – 66% since the mid-1990s – has led to it being moved from ‘vulnerable’ to ‘endangered’ conservation threat status by the Botanical Society of Britain and Ireland (BSBI). It is the first ‘vascular’ plant – a grouping that includes flowering plants and ferns – to become endangered due to climate change, the BSBI said. The study found that drooping saxifrage and mountain sandwort have both declined by over 50%.

Sarah Watts, former seasonal ecologist with the National Trust for Scotland, analysed data from 40 years of monitoring for ten rare plant species on Ben Lawers National Nature Reserve. Prior to becoming a PhD researcher at the University of Stirling she spent 12 years monitoring species alongside other Trust staff and volunteers, adding to a unique data set.

“Our research signals a rapid loss of biodiversity happening right now which means that, if it’s allowed to continue on this accelerated trajectory, due to climate change, we will see the extinction of species like these.”
Sarah Watts
University of Stirling

Ms Watts added: ‘What we are seeing here is range contraction – where species that grow in cold places, in the north and at high altitude, are moving further north and higher up the mountain. But at some point, they’ll have no further to go and will disappear. For example, drooping saxifrage is now only found 50 metres from the top of Ben Lawers.’

Ms Watts said the global rise in temperature due to climate change had led to lowland species colonising upland areas and outcompeting the mountain plants, reducing the area they can grow in. And loss of snow cover due to climate change has also removed plants’ protection from freeze-thaws, which cause land slip and rock fall, destabilising the arctic-alpine habitat.

“This quantitative analysis of the Trust’s monitoring data highlights the dramatic decline in some of our rarest specialist mountain species. Unfortunately, declining trends have also been recorded for some mosses and liverworts also adapted to high altitudes.”
Helen Cole
Ben Lawers Property Manager
A woman stands on a mountainside, taking notes on a pad of paper balanced on her knee. A loch and mountains can be seen in the background. The sun's rays gleam through the clouds.

At 1,214 metres, Ben Lawers is the 10th highest peak in Britain and is rich in alkaline soils, which makes it a haven for rare plants. Ms Watts said: ‘Ben Lawers is the most southerly site in Europe where snow pearlwort grows, and the only one in Britain. Elsewhere, it’s found in the Arctic and in northern Scandinavia, in places like Svalbard.

‘Mountain outpost sites such as Ben Lawers, at the edge of the global range of arctic-alpine plants, are unique biodiversity hotspots. These plants have high cultural and inspirational value, and may have unique genetic variations which will be lost forever when they go.’

However, she has some suggestions as to how the species could be preserved: ‘Development of ex-situ plant conservation collections of these threatened species, in collaboration with expert horticulturalists working at botanical gardens, will be of critical importance for preserving the Scottish Highland populations before they become extinct in the wild.

‘These collections would also allow us to conduct further research into the factors affecting the plants’ survival or decline, and could be used for translocations and assisted migrations to more suitable mountain habitat in the future.’

I love this place, I leave no trace

Donate now