For the past week, I’ve been forcibly removed from the mainstream world, isolated with a small group of fellow ecology students in the southern Scottish Highlands. Fortunately, the landscape and wildlife were more than compensation – as well as seeing numerous rare and range-restricted plants, I added eight new bird species to my list, and managed to see pine marten and red squirrel for the first time. To give you an idea of what we got up to, I’m going to be running a series of weekly features discussing some issues that became apparent during the field trip, starting with this post.
The most characteristic feature of the Highlands is (pretty obviously) their height – the region contains the highest peaks in the UK, the only areas of the country over a kilometre above sea level, and it shows in the wildlife. The heathland that caps the tall mountain slopes and plateaus is a mix of sedges (primarily Carex bigelowii) and woolly hair moss Racomitrium lanuginosum. This assemblage is more typical of arctic tundra than British countryside, but the cold winter temperatures and short summer growth period mean they aren’t ousted by more competitive plants like heathers, which are only found on the lower, warmer slopes. Following the end of the most recent ice age, some 10,000 years ago, this plant community would have been found across the UK, retreating northwards and uphill with the ice as the temperature warmed. The same story applies to some animals – the mountain ringlet butterfly, Erebia epiphron, is restricted to the Highlands and the Lake District (only on mountains over 500m tall). The rock ptarmigan, a grouse ubiquitous throughout Scandinavia, is found only on the highest-elevation scree slopes in Scotland, where their rock-like summer camouflage allows them to evade predation. Other species, including the dotterel (a wading bird related to lapwings and other plovers), and the blackbird-like ring ouzel, seem to be more sensible, migrating to the isolated uplands in summer to breed in relative safety, then returning to overwinter in Morocco; for these species, the Highlands provide the largest single breeding area in the UK.
This combination of unusual species makes the Scottish Highlands unique in the UK, the last remaining refugium for many species trapped here when the North Sea rose after the ice age. Few sheep are grazed on the high peaks, and red deer rarely make their way so high; there is no heather burning, no tree planting, and no artificial fertilisation of the soil (not on purpose, at least – some nitrogen is deposited from atmospheric pollutants released from vehicle exhausts). This might well be the most pristine and undisturbed habitat in the British Isles, but it is still vulnerable to that most insidious of manmade threats: climate change. The year-on-year increase in average temperature recorded over the last few decades might be good news for species restricted to the southern lowlands, allowing them to expand their range as long as habitat is available – and sometimes do better than in their old range, such as brown argus butterflies outrunning their parasites . Conversely, for ptarmigan and species like them, stranded on tall mountains, the situation seems dire. Each year the thermocline moves upwards, and the patches of mountains available to them shrink. Think of it like a low island in the rising tide: once the island’s gone, it’s gone. If you’re still looking for evidence of climate change, talk to the sheep herders who haven’t found dead ptarmigan on their land in decades.
So what can be done? Fortunately, the inevitable end seems to be a while away yet, with the arctic-alpine ecosystem clinging to the cool, shady northern faces of high mountains for the next few decades. This gives us precious time to act. However, the same story is repeated over and over, in every mountain range, all across the world. Where there are glaciers, they are retreating. Where there is a winter snow cap, it is falling later and melting earlier. Only a global solution will fix this global problem, so next time you get the opportunity to reduce your carbon footprint, think of the ptarmigan.
Until next time, when I’ll be covering the impacts of habitat management on Scotland’s four grouse species,
 Mendendez et al. (2008) Escape from natural enemies during climate-driven range expansion: a case study. http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2311.2008.00985.x/abstract;jsessionid=1522488BB315D1DE7CA9DF0D9F85C680.f02t02