Rare arctic-alpine plants becoming endangered on Ben Lawers

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.

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.