Numbers collapse despite good weather
This year’s Big Butterfly Count results are in and make grim reading.
Some common species saw their numbers collapse over the summer, despite the UK experiencing weather conditions that usually help them to thrive.
More than 38,000 counts were completed with 396,138 butterflies logged – the world’s largest count of butterflies.
Gatekeeper, Comma and Small Copper butterflies experienced their worst year in the project’s history, with sightings down 40 per cent, 46 per cent and 30 per cent compared to last year. The Small Tortoiseshell saw a 47 per cent drop in numbers and Peacock slumped by 42 per cent with both species recording their second worst years.
Most participants saw fewer butterflies per count than ever before (I took part – I saw none in the time frame allowed, although there was a burst of sightings after the final deadline).
The mild winter and cold spring could be to blame. Intensive farming and pesticide use are also possible culprits, say the organisers.
While the long-term trends of butterfly and moth numbers tend to result from human activities such as habitat destruction and climate change, short-term changes, from year to year, butterfly generation to generation, are typically caused by natural factors such as the weather and populations of parasites.
So, in cold, wet summers, such as in 2012, butterfly populations often crash, while in good summers, such as 2013, they bounce back.
The results of this year’s Big Butterfly Count, however, don’t fit this pattern. It was a pretty good summer across the UK, with above-average temperatures and yet butterflies on the whole fared badly.
The average number of each insect of the 20 target species seen per 15-minute count was the lowest recorded since the project began in 2010. Just 12.2 individuals per count were recorded, down from 13.4 per count in 2015, 14.7 in 2014 and a whopping 23 per count in 2013.
More than half of the target species decreased in 2016 compared with the previous year. The ‘blues’ did badly, with Small Copper recording its lowest numbers since the count began and the Common Blue and Holly Blue halved in numbers since last year.
The Peacock decreased for the third summer in a row. Its numbers have now dropped from an average of 3.6 individuals per count in 2013 to just 0.5 per count in 2016.
Small Tortoiseshell numbers were down once again too, falling by 47 per cent from 2015 levels, and even the Comma, one of the success stories of the past few decades, fell 46 per cent year on year.
The Gatekeeper, the most abundant species in 2015’s count, suffered a 40 per cent decrease, finishing in fourth place, with an average of just 1.5 Gatekeepers per count.
It wasn’t all doom and gloom, however. Seven species were counted in greater numbers than last year. Red Admiral was 70 per cent up year on year, the biggest increase of any target species. Another winner was the Green-veined White, up 58 per cent on 2015. It did especially well in Scotland, Northern Ireland and Wales.
One further positive was that the average number of individuals seen per count in 2016, increased in Northern Ireland and Scotland compared with the previous year, despite the overall UK average reaching its lowest ebb.
The Large White, with the Small White moving up from fourth to second place, while Meadow Brown retained third place. Ringlet and Marbled White both achieved their second highest rankings since the count began.
The 2016 results for the 20 Big Butterfly Count target butterfly and moth species (numbers refer to each sighting and percentage increase/decrease since last year:
- Large White, 62890, +2%
- Small White, 61955, +15%
- Meadow Brown, 57281, +1%
- Gatekeeper, 47597, -40%
- Ringlet, 26968, +32%
- Red Admiral, 26568, +70%
- Peacock, 18508, -42%
- Green-veined White, 16879, +58%
- Small Tortoiseshell, 12335, -47%
- Speckled Wood, 10271, +12%
- Marbled White, 9461, +58%
- Six-spot Burnet, 8417, +20%
- Large Skipper, 8182, -2%
- Comma, 7514, -46%
- Common Blue, 5938, -55%
- Painted Lady, 4246, -23%
- Holly Blue, 3969, -48%
- Brimstone, 3629, -20%
- Small Copper, 2286, -30%
- Silver Y, 1244, -12%
The Big Butterfly Count will take place again next summer to enable conservationists to find longer-term trends in UK butterfly species.
For more information, including an interactive map, and to give to the fund-raising appeal, go to www.bigbutterflycount.org.