IIt was a long hike up the steep, rocky trail, on an unexpectedly warm day, but it was worth the effort. Along the banks of a stream, on the slopes of Ben Lawers in the Scottish Highlands, I finally found my prey.
A small, unpretentious, chocolate brown butterfly with a row of orange-rimmed black spots on its wings: the mountain ring. For me, this marked a milestone in natural history – the last of the 61 regularly occurring butterflies in Britain that I had yet to see.
As the name suggests, the mountain ringlet is our only truly alpine butterfly, found above 350 meters, or roughly 1,150 feet, in the Lake District and in the Highlands. Here, it waits patiently in its hiding place in the kills grass, sometimes for days, until the sun rises. Only then does it emerge, fluttering fast and low on the ground, stopping occasionally to bask in the sun.
When guardian Writer Patrick Barkham set out on his quest to see all the British species, documented in his delightful book. The butterfly islands, managed to complete the task in less than a year. It has taken me almost six decades, if I include the common butterflies that I remember seeing as a child; or 20 years, from the first time I took the idea of completing the set seriously.
But Patrick only aimed to see 59 different butterflies, while I have two more on my list: the large tortoise shell and the long-tailed blue. Both have taken hold in the UK in the dozen years since Patrick’s “butterfly hunt” in 2009. This couple are recent immigrants from continental Europe, brought across the English Channel by warm southerly winds, having expanded for the first time its ranges to the north as a result of global warming.
Seeing both, the great tortoiseshell on Dorset’s Portland Bill and the long-tailed blue near Brighton, was quite exciting for me. But I also felt a foreboding, as I do when I come across flocks of Cattle Egrets, now a regular sight near my Somerset home. This is because while these continental creatures colonize Britain from the south, species from the north, such as the mountain ridge, will soon be disappearing.
We have always known that some species will manage to cope with a rapidly warming climate: those that are already common, widespread, and capable of adapting to live in a wide range of habitats and cope with different climatic conditions. But we are also increasingly aware that highly specialized species, such as the mountain curl, are likely to become victims of their own narrow niche.
Scientists believe that the mountain curl was one of the first butterflies to recolonize Britain, around 12,000 years ago, after the end of the last Ice Age. To survive the cold, humid and fickle conditions in their highland homes, the caterpillars adapted by slowing down their life cycle: it took two whole years before they pupated and then emerged as adults.
But as temperatures rise and landscapes change, the corner of the mountain simply has nowhere to go. Those who live at the southern tip of their range in the UK, in Cumbria, are already struggling. Populations have moved 150 m uphill in the last 50 years; And if we cannot limit temperature increases, they are likely to disappear entirely within the next half century. As a leading butterfly expert Matthew oates notes: “Change is now the norm, the real problem is its pace. We can no longer take anything for granted in the natural world, even in something as permanent as a mountain. “
The mountain ringlet is not the only high-altitude species facing the threat of extinction in the UK. A specialized set of fauna and flora can still be found in the Cairngorms, Britain’s only true Arctic-Alpine biome. These include several iconic Scottish creatures: the mountain hare, the snow pennant, and the white partridge, the only British bird that turns almost entirely white in winter.
As for the mountainous loop, rising temperatures are allowing the more generalist plants and animals to climb the slopes of the mountains, where they first compete with the more specialized montane species and then expel them.
So what can be done to try to stop, or better yet reverse, these declines? One proposal is to move the mountain loops of the Lake District to new homes at higher altitudes in the Highlands; although conservationists are concerned that this could lead to the unwanted mixing of genetically distinct populations. Another solution, much faster and simpler, is to allow the grass in the butterfly habitat to grow more, mitigating the warmer temperatures by creating cooler microclimates, where the butterflies can find refuge.
But this feels like we are playing on the edges of the problem. As we know, the real issue is how we limit overall global warming to 1.5 ° C while mitigating any negative effects on wildlife. As recent events here and abroad have shown, the consequences of rapid climate change are already with us. And as this week’s Met Office report warns, the climate crisis will inevitably lead to even more unpredictable and extreme weather here in the UK; which can only be bad news for creatures already living on the edge.
So while I allowed myself a congratulatory drink to commemorate seeing all the species of butterflies in Britain, that celebration was tinged with sadness; the fear that, in my own lifetime, the last one on my list might finally be doomed.
Stephen Moss is a naturalist and author, and leads the Master of Nature and Travel Writing at the University of Bath Spa. His latest book is Skylarks with Rosie: a Somerset Spring (Saraband)
George is Digismak’s reported cum editor with 13 years of experience in Journalism