Red admiral butterfly numbers given a boost

There’s been a sharp rise in the number of Red Admiral butterflies in the UK. The charity Butterfly Conservation has enlisted the help of the public to count them and they think that there has been a rise of more than 300% on last year. Chris spoke with Zöe Randle, senior surveys officer at Butterfly Conservation...

Zoe - What we've done is we've enlisted the help of the general public. We've run the Big Butterfly Count, it's the largest annual citizen science project on butterflies in the world. And we've had over 125,000 counts submitted by almost 90,000 people. So thanks to everyone that's taken part. They've counted in excess of 247,000 Red admiral butterflies.

Chris - So people just go out in their garden or in their nearby park and they're totting up how many butterflies they see in what, an hour or something? Is that how it works?

Zoe - It's not even an hour. Anyone can take part. It's dead easy. All you need to do is spend 15 minutes in a warm, sunny spot and count the different types of butterfly that you see. There's an identification guide on the Big Butterfly Count website that people can download to help them identify the species that they see. And there's also a mobile phone app as well. You can log your counts there or on the Big Butterfly Count website.

Chris - So two questions we need to explore then is, first, why the Red admirals have shot up so much, and then what's happening to the other species. We'll look at that second. So tell us about the Red admirals first. Why do you think they've gone up so much?

Zoe - Well, the Red Admiral is traditionally thought of as a migrant species. It's a summer visitor to our shores. It normally lives in the Mediterranean and North Africa, and they've evolved a survival strategy which helps them track their food plants. So they will move into areas where their food plant is more abundant to escape the summer droughts that are coming in their native lands. But, more recently, the Red admiral has been found to be breeding in the UK and it can survive our winters. So the long term trend for this butterfly from the UK Butterfly Monitoring Scheme is an increase in abundance of 234% and 15% in distribution. And we believe that climate change is driving the increase in numbers that we've seen in the UK this year.

Chris - Where there are winners, there are inevitably losers. Does this mean that some other species that perhaps rely on a cold snap are not doing quite so well?

Zoe - Yeah, that's absolutely right. Climate change is beneficial for some species and detrimental to others. So for example, in Scotland, we've got the Scotch argus butterfly and, as the name suggests, it's primarily found in Scotland. There are a couple of sites in northern England, but what we're seeing is that the butterfly is trying to escape the heat. And what it does is it shifts its range northwards, so it's moving further northwards in Scotland and retracting from those southern ranges. And it's also going up to higher elevations as well to escape the heat. So once you get to the north coast of Scotland, there's not really anywhere for you to go. And once you get to the top of the mountain, where does the butterfly go? So it's a mixed bag. Also, climate change is beneficial for some species. It does enable them to move northwards. But, to habitat specialist species, for example, the Duke of burgundy, the Pearl-bordered fritillary, they can only move northwards and take advantage of climate change if there's suitable habitat in the new envelope of places that open up to it.

Chris - Are we seeing that there are some endangered species that climate change is turning out to be a silver lining to the cloud? As in, it opens up more space for them, more opportunities, more niches. So their numbers are perhaps being rescued?

Zoe - Well, that's right. The work that we're doing at Butterfly Conservation is targeting landscape scale conservation work to benefit these other species. And we are seeing increases in rare species. But let's look at the overall picture, and that is, unfortunately, 80% of the UK's butterflies are declining in number or where they're found. So it's not all good news for all species.