Research by the National Trust for Scotland shows rare mountain plants in the Highlands and islands are retreating higher or disappearing entirely

This article is more than 4 years old

This article is more than 4 years old

There is clear evidence that some of Britain’s rarest mountain plants are disappearing due to a steadily warming climate, botanists working in the Scottish Highlands have found.

The tiny but fragile Arctic plants, such as Iceland purslaine, snow pearlwort and Highland saxifrage, are found only in a handful of locations in the Highlands and islands, clustered in north-facing gullies, coires and crevices, frequently protected by the last pockets of late-lying winter snow.

A series of studies by the National Trust for Scotland (NTS), the historic building and landscape charity, has found these plants – relics from the last period of glaciation, are retreating higher up the mountainside or disappearing entirely. In some cases they are being replaced by grasses previously found at lower, warmer altitudes.

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Iceland purslane, an Arctic species which is extremely rare in the UK and found only on the Hebridean islands of Skye and Mull, nestles in protected spots on areas of volcanic basalt at heights above 400m.

Surveying on the Burg peninsula of Mull had found the tiny annual plant was being severely hit by increasingly warm springs, which had also led to increased growth by other plants competing for space.

On Bidean nam Bian next to Glencoe in Argyll, the latest field surveys found a 50% decline in Highland saxifrage at lower altitudes compared to the numbers detected in 1995.

Their surveys on Ben Lawers, a 1,214m high peak on Loch Tay in Perthshire which is regarded as a mecca for botanists, had found “a very worrying decline” in the numbers of snow pearlwort. An inconspicuous cushion-forming flowering plant, it which only survives in the UK on Ben Lawers and several places in the surrounding Breadalbane mountains at heights above 900m.

Sarah Watts, a seasonal ecologist for NTS, said the plant was at the southern limit of its natural range on Ben Lawers. Half of the sites found in 1981 had now become extinct, although heavy snow in the recent winters had helped halt the effects of climate change.

“It’s definitely the species we are most worried about in terms of climate change,” she said.

Facebook Twitter Pinterest In pouring rain and with the support of expert climbers, botanist Dan Watson abseils down the Great Chimney on Tower Ridge where he finds a cluster drooping Saxifrage at the base. Photograph: Murdo Macleod/The Guardian

Dan Watson, an ecologist with the NTS overseeing the trust’s survey work, said: “When you see mountain plants either retreating up the hill or disappearing from their niches, it’s clear evidence that things are changing. The evidence is unequivocal to me that the climate is changing in the mountains.”

Ecologists and botanists working with NTS, Scottish Natural Heritage and conservation charities are now investing heavily in a series of intensive studies to map and track mountain plants, collaborating in some cases with highly skilled mountaineers.

Watson was part of a large group of botanists, geologists and mountaineers who spent last week dangling from ropes to survey unexplored areas of the exposed and often sheer north face of Ben Nevis, Britain’s highest mountain, in a search for similar species.

Facebook Twitter Pinterest Drooping saxifrage found in a gully. Photograph: Murdo Macleod/The Guardian

Their survey on the 1,346m-high mountain was the last in a series of three expeditions by the Nevis Landscape Partnership, a conservation and tourism charity based in Fort William.

Freja MacDougall, a spokeswoman for the partnership, said they had discovered Alpine saxifrage in new locations – the plant had not been detected on Ben Nevis until their first survey in 2014, tufted saxifrage and the rare drooping saxifrage in seed.

They found new populations of Highland saxifrage, as well as the white-flowered Arctic mouse-ear, a plant native to Greenland, Iceland and Norway, and starwort mouse-ear, plus a mystery grass which botanists are now trying to identify.

Overall, the collection of plants they found was in favourable condition because these surveys had been intensive enough to provide far more authoritative results than had been available before, MacDougall said.

Watson said to accurately map the health and size of these plant populations was essential: it allowed ecologists to trace the impacts and speed of climate change with far greater precision.

Some of the historic field data compiled since the 1950s which the NTS relies on is patchy, with different techniques used by different teams.

Facebook Twitter Pinterest Female dwarf willow on Tower Ridge. Photograph: Murdo Macleod/The Guardian

But data from the fieldwork carried out in the last 20 years on each species corroborated findings from others. “It is the weight of evidence rather than anything utterly conclusive. A lot of things of happening in the same direction,” he said.

“It’s a pretty clear indicator that things are changing and the wider repercussions that climate change will have in terms of all the issues we are familiar with, rising sea levels and fast changes in the ecologies of some areas. It’s an indicator of that,” he said.