A short history of Scotland's lost species 5: The Alpine Blue-Sowthistle

During this series of blogs, I talk about some species that Scotland lost, but subsequently regained, and others that have yet to make a reappearance (and may never). I’ll also focus on some species which have come perilously close to being wiped out but just managed to hang on. This blog is about one of the latter; a fine example of charismatic mega-flora, but one that most people will never have heard of – the Alpine Blue Sow-Thistle (Cicerbita alpina).

This handsome, purple-blue-flowered herb can grow up to a metre and a half tall and is found in Europe in the Nordic countries and some mountainous areas further south, such as the Alps and Pyrenees. In the UK, the last remnant populations are found at just four sites, all in the Cairngorms National Park, ranging in altitude from 700m to 1090m.

Given that today it’s found only on rocky ledges, you could be forgiven for thinking that the species is a montane specialist that needs lofty crags and cliffs high above the tree-line in order to thrive. However, the evidence suggests that in Scotland the species has, over many years, retreated to refugee habitat, i.e. inaccessible ledges safe from grazing animals such as deer, sheep and goats. A clue that the current habitat is less than ideal is that by the time flowering occurs in July and August the plants are often battered by exposure to the wind and have browning leaves. Indeed, a fifth Scottish population, also in the Cairngorms, was found in Canness Glen at an altitude of just 530 m, but nevertheless it appears to have gone extinct in the 1970s.

The plant's Achilles heel is its palatability. Its big, succulent, heart-shaped leaves are sought after by a wide range of organisms, from slugs to sheep, and reindeer to elk. Bears are known to gorge on it, and in Finnish one of the plant’s names is P?pp?hein?, literally ‘bear-hay’ (P?pp? is one of over 200 names that Finns have given to the brown bear). Humans would also have eaten it, sometimes cooked in reindeer milk, sometimes raw like a salad (its name in French, la Laitue des Alpes, translates to ‘alpine lettuce’). Because the species is so vulnerable to herbivores, it acts as something of an indicator species for the ecological health of the uplands - a canary in the mineshaft of grazing pressure.

The Highlands of Scotland have been subjected to relatively high levels of grazing for many centuries. We know from surviving records that many thousands of sheep, goats, cattle and horses were grazed in the mountains between spring and autumn by subsistence farmers taking their livestock up to the summer shielings from lower-lying ground. This age-old way of life was, however, replaced in many areas in the late 18th and 19th centuries by commercial sheep ranching. In subsequent decades deer stalking joined, or took over from, hill sheep farming as the prevailing upland land use in many areas, giving rise to densities of red deer very rarely experienced in other mountainous parts of Europe. As recently as the 1930s, shepherds in the Angus glens were deliberately releasing goats onto precarious ledges to graze down the vegetation so that their less sure-footed sheep wouldn’t be tempted onto them, whereupon they might get stuck. Over time, all of these land uses are likely to have had a profound effect on a plant species so favoured by a wide range of herbivores and omnivores. It seems very likely the species would have once been much more widespread in the Scottish Highlands.

In Norway, including in the south-west where climate, soils and altitudes are very similar to the Scottish Highlands, the alpine blue sow-thistle is commonly found, often in profusion, amongst the damp soils and partial shade of pinewoods and birchwoods. While it can be found on inaccessible ledges there too, it is clearly a species adapted to a wider range of circumstances than currently seen in Scotland. In the absence of the dappled shade of trees in Scotland, aspect is crucial for providing the sow-thistle with the ground conditions it needs. The four sites in Scotland are all on north- or east-facing slopes where late-lying snow and the relative lack of direct sun help to keep the ground moist.

The sow-thistle’s current separation from woodland in Scotland is probably a fairly recent phenomenon. A map drawn by Timothy Pont in the 1590s showing the area around the now treeless, neighbouring Caenlochan and Canness glens (home to one of the four remaining populations, as well as the site of the now-extinct, fifth population) shows that a woodland, called the ‘Wood of Stron-Riach’, filled those glens at the time. Just as with radiocarbon dates though, map depictions are a mere snapshot in time – it’s very likely that the extent of the woodland shown in the 1590s had already greatly diminished. Previously, the sow thistle probably also grew lower down the mountainsides, while the woodland had probably extended higher up.

An excerpt from Timothy Pont’s late 16th century map showing the now-missing Wood of Stron-Riach in Caenlochan and Canness glens. Reproduced with the permission of the National Library of Scotland.

Genetic research has shown that the four remnant populations are in-bred, producing very little seed and instead reproducing clonally. However, staff at the Royal Botanic Garden Edinburgh (RBGE) have recently successfully crossed plants from all of the four populations to improve genetic diversity. Some of the resultant plants have been experimentally translocated back into the wild to create new populations in the Cairngorms. The sites chosen cover a range of habitat types, including on ledges protected by deer fencing but also in open native woodland where deer densities are low. Hopefully this work will have a positive outcome, giving hope for a more promising future for this tough but beleaguered mountain beauty.

To see a summary of recent conservation action, including some very intrepid planting work, see this short video narrated by Dr Aline Finger of the RBGE: https://www.youtube.com/watch?v=9xn7eJkUuwk

My previous articles on elk, bear, crane and reindeer are available via https://www.dhirubhai.net/in/david-hetherington-9b067b72/detail/recent-activity/posts/