British butterfly numbers plummet in 2024

The UK’s butterfly population has declined markedly this year, largely, conservationists speculate, because of a lack of sun and too much rainfall earlier in the year. The charity Butterfly Conservation says that this is part of a worrying trend that has seen the numbers of four out of five of our native species decline steadily since the 1970s. To find out more, we put in a call to BBC’s security correspondent who is also, as it turns out, a butterfly authority and enthusiast: Frank Gardner…

Frank - It's been a pretty miserable disappointing year for butterflies in the uk. On the whole, the numbers are down and the number of species that people are seeing generally I think are down. In my case, I have only seen 21 species out of the 59 resident species, approximately, that we have in this country. Last year I saw 34. There are plenty of people who've spent a lot more time than this than me that will see a great deal, many more than that. But there are some species that I never saw. Orange tip this year for example, which I've always seen in previous years. I haven't seen small copper. Particularly absent has been small tortoiseshell, they've been declining really since 2000. And they've got a particular problem I'm told, which is that they suffer from a parasite called Sturmia bella, which came over from France around the turn of the century in 1999. And that lays its eggs quite close to the caterpillars, which then eat them along with the leaves. And that really damages the numbers.

Chris - Is it the same sort of story for the others that are down on numbers and they've also got some kind of parasite challenging them or is it a range of factors or is this just a one off?

Frank - It's a range of factors. It's been a very wet spring and that has affected, well, it's affected the leaves because they don't like damp. Wet leaves, habitat loss, habitat fragmentation, climate change, associated change in weather and pesticide use. There are a couple of species that have done better this year. Brimstone and holly blue and they, I'm told, are coming over from Europe, from the continent. One of the mysteries is a species called black veined white, which we saw photographed on the outskirts of London last year. And we still don't know exactly where they appeared because they've been extubated, i.e. vanished, from the UK since 1925. This is the first sighting of them in a hundred years. They're very common on the constant. They occur in Calais, but they haven't been here for a long time. And the suspicion was that somebody had done an unauthorised release, but locals in the area, and they saw about 30 altogether, are convinced that a female flew over from France, laid her eggs on the hawthorn, on blackthorn bushes. And they hatched out last year. And they'd been seen again this year early in the summer in May, June.

Chris - One good news story I suppose. But whenever there is a loss of one species, there are almost always knock-on consequences. There are migratory birds that arrive hoping there's going to be caterpillars to feast on. If the butterflies don't have sufficient numbers, then that means birds go unfed, which means that they then see a decline as well. So it's sort of a domino effect, isn't it?

Frank - It really is the whole sort of cycle. The food chain is very much susceptible to changes in weather and in habitat. So one of the reasons why we have fewer butterflies is also because there's not as much habitat for them. As cities grow, as open, wild spaces are taken up with urban development.

Chris - Presumably, a lot of those factors are not easy to reverse quickly. Are there any sort of practical things that we can do to at least try and slow down the decline, if not, stop it.?

Frank - Wild spaces is important and not disturbing those habitats, letting them just get on with it. The figures that Butterfly Conservation, the UK charity, have a pretty depressing, they're saying that since the 1970s, 80% of butterfly species in the UK have declined. And they were saying for those of us aged about 40 or above. We'll remember seeing a lot more butterflies around where we were children than now.