Mediterranean egrets balancing on the backs of cows, multicoloured moths the size of a human hand, and impossibly exotic bee-eaters hawking for insects under English skies. All are here as a direct consequence of the climate crisis, which has allowed continental European species to extend their ranges northwards, and then make the leap across the Channel to gain a foothold in southern Britain.

Whenever I take a walk along the disused railway line across the Avalon marshes, near my Somerset home, I can’t help noticing these new arrivals. Tall and elegant, great white egrets first arrived here from France just a few years ago; now I encounter them every time I visit. Down the road, at the Somerset Wildlife Trust’s reserve at Catcott Lows, flocks of cattle egrets – the same species we see in wildlife films from Africa – gather to feed, perched appropriately on the backs of cattle. Elsewhere on the marshes, secretive night herons and little bitterns have also bred in recent years.

A great egret takes off from the Greylake RSPB reserve on the Somerset Levels. Photograph: Mike Read/Alamy

When I moved to Somerset with my young family just over a dozen years ago, all these species were so rare they would have attracted a crowd of eager twitchers. Today, everyone – including my own teenagers – takes them for granted.

Going back to my own childhood, the now ubiquitous little egret – that Persil-white apparition featuring at a wetland near you – was incredibly scarce. When, at the age of 10, I stumbled across one on Brownsea Island in Dorset, it was the highlight of my birding life for many years afterwards.

Long-tailed blues could be seen all along Britain’s south coast in August. Photograph: Neil Hulme/Butterfly Conservation

And it’s not just birds. When it comes to unexpected new arrivals, butterfly and moth enthusiasts have enjoyed a bumper year. First came the news in August that an invasion of long-tailed blue butterflies was occurring all the way along the south coast, from Cornwall to Kent. This unusual looking butterfly – which really does have a tiny “tail” protruding from the back of each wing – was turning up in the most unexpected places: Sussex butterfly expert Neil Hulme even found one laying eggs on pea plants in a pub garden. Thanks to Hulme’s guidance, even I managed to catch up with them, in the equally unlikely setting of a patch of waste ground next to Brighton racecourse.

Meanwhile, that group of nocturnal activists known as “moth trappers”, of which I am one, have been attracting some real beauties to their light traps. The greatest prize this summer has been the wonderfully named Clifden nonpareil – literally meaning “beyond compare”.

One of our largest and most spectacular moths, with a 12cm wingspan and a bright blue flash on its underwings, it was once considered extinct in Britain. Yet this summer, after an absence of many years, the Clifden nonpareil has been turning up in moth traps all over southern England and Wales.

Its day-flying counterpart, the hummingbird hawkmoth, has also had a good year, as has one of our most mysterious and sought-after species, the death’s-head hawkmoth.

Made famous – or perhaps that should be infamous – by the novel and film The Silence of the Lambs, several death’s-head caterpillars and pupae have been found in potato patches in the Somerset village of Westbury-sub-Mendip.



A death’s head hawkmoth with its distinctive skull pattern. Photograph: David Chapman/Alamy

Brought indoors by local naturalists, they were successfully hatched out, the adult moths revealing the sinister skull pattern on the back of the thorax that gives the species its name. When I went to see this extraordinary insect, it emitted its famous “squeak”, which adds to its terrifying reputation.

It’s not just these new arrivals that indicate the effects of climate change – or as we now more correctly call it, the climate emergency. Many resident bird species are rising in numbers; as are short-distance migrants such as the blackcap and chiffchaff. These small, neat warblers are now overwintering in Britain (instead of Spain and north Africa), thanks to milder winters, and the consequent wider availability of their insect food.

Blackcaps are now spending winters in Britain instead of Spain and north Africa. Photograph: David Whitaker/Alamy

So, in Voltaire’s ironic comment, all is surely for the best, in the best of all possible worlds. For the moment, that may indeed be true. Yet as long ago as 1990, the German ornithologist and migration expert Peter Berthold warned that during the initial warming period many bird species would benefit from “heavenly conditions”. This, he explained, was a kind of honeymoon period in which warmer springs and summers, and milder winters, would allow them to expand their numbers and range.

But if the global climate becomes hotter still, with more frequent and extreme weather events such as droughts, storms and floods, reality will inevitably begin to bite, and all but the most adaptable species will start to decline. Their fall might also be hastened by an increase in populations of parasites and diseases, which flourish in warmer climates.

Ironically, the long-tailed blue butterfly I watched sunning itself in August cannot survive Britain’s winters – at least not yet. As Neil Hulme explains, it would need a rise in average temperatures of several degrees, enough to banish winter frosts that kill their larvae, to colonise Britain permanently. But if that did happen, we would have reached a climatic tipping point, and probably lose not just much of our wildlife, but even jeopardise our own long-term existence on the planet.

The underside of a long-tailed blue butterfly. Photograph: Neil Hulme/Butterfly Conservation

Rapid environmental change is likely to hit some creatures harder than others. On a recent edition of the Radio 4 series The Life Scientific, Professor Anne Magurran of St Andrews University talked about what she calls “the shopping mall effect”. She noted that wherever you go in the world nowadays, from London to Los Angeles, Madrid to Melbourne, shopping centres tend to have the same outlets – well-known international brands whose names we all recognise.

Likewise, in response to a panoply of environmental pressures, ecosystems are tending to become more homogenous, with a few highly adaptable species beginning to dominate to the exclusion of less successful ones. As Magurran warns, if environmental conditions become more and more extreme, homogenisation will start to occur, and there will inevitably be species loss.

However, as Magurran points out, there is still time for us to take action to help safeguard the earth’s biodiversity. At the moment, she says, the dominant signal is change rather than loss. But unless we take swift and decisive action to mitigate climate change, while at the same time preventing habitat destruction, the rate of extinction will start to accelerate. Given that many governments appear to be heading in the opposite direction, with increased deregulation and a weakening of environmental protection back on the agenda, this is a very real concern. If we fail to act, the consequences for Britain’s wildlife are that successful generalists will do well, while specialists will not.

When it comes to making predictions, we also need to take into account the unusual nature of the British Isles, which stretch from Shetland, just a few degrees of latitude short of the Arctic Circle, to Scilly, which has its own – almost subtropical – microclimate.

So, while we enjoy the short-term benefits of climate change in the south, problems are already beginning to occur at the other end of Britain. On the Cairngorm plateau, our sole example of the arctic-alpine biome, the ptarmigan – the only British bird that turns white in winter – is gradually declining, with just a few thousand pairs remaining.

Until the start of the 19th century, the ptarmigan could be found across a wide swathe of northern Britain, south to the Lake District; but today it survives only in the Highlands. Its decline has been caused by a number of factors, including crows attracted by the rubbish left by visitors, which prey on the ptarmigan’s eggs and chicks. But a more long-term factor is the warming climate, which is altering the habitat and food supply of these highly specialised birds.

Only a few thousand ptarmigans remain in the Highlands. Photograph: Christoph Ruisz/Alamy

Should the climate emergency continue to worsen, and temperatures keep rising, the ptarmigan – along with other highland specialists such as the dotterel and snow bunting – looks set to disappear as a British bird in my lifetime.

I recall many years ago hearing someone talk about saving the planet “for our children, and our children’s children”. At the time, this felt like an abstract notion; even a rather sanctimonious platitude. Now that I have children and step-grandchildren of my own, who may well live to witness the 22nd century, that phrase feels far more relevant and urgent. If the worst predictions for the climate emergency come true, with devastating consequences for human and animal life on this planet, then I do not envy them living that long.

So, much as I enjoy seeing cattle egrets on my local patch, or catching up with a new species of butterfly on the south coast, my pleasure is more than ever tinged with concern.

My fear is that these pioneering colonists are not something to be celebrated, but a phenomenon to warn us of impending disaster in this new age of extinction.

• Stephen Moss is a naturalist and author based in Somerset, where he is president of the Somerset Wildlife Trust; he also runs an MA in travel and nature writing at Bath Spa University