Cold weather in April ensured a poor year for butterfly numbers
Two declining butterflies suffered their worst year on record in 2017, the UK Butterfly Monitoring Scheme has found. It was hoped that butterflies would bounce back after a bad year in 2016, but although last year’s numbers were up, they were still well below average, with 2017 coming in as the seventh worst year on record overall.
There were hopes for a good butterfly year as many species emerged earlier than usual following a warm start to 2017 – but a cold snap at the end of April put paid to that. The second half of last summer was cloudier and wetter than average, causing further problems.
Records date back to 1976, and seven of the worst 10 years have occurred this century. While long-term falls in butterfly populations have been caused by habitat loss, scientists attribute the dramatic recent decline to climate change, pesticides such as neonicotinoids, and nitrogen pollution. The caterpillars of many species feed on plants which are easily swamped by more vigorous grasses, which thrive in high-nitrogen conditions.
Grayling numbers have fallen by 63% over the last decade. Picture: Patrick Clement/Butterfly Conservation
The grizzled skipper (main picture) and grayling (above) had their worst year on record for the second year running. The grizzled skipper was down 9% compared to 2016 and its population has now more than halved since the 1970s, while the grayling declined by a further 6%. It wasn’t just rare species that struggled; the large white – about which gardeners have decidedly mixed feelings – saw its numbers fall by 19% and is now also in a state of long-term decline. The other two ‘cabbage’ butterflies also had a poor year; the small white was down 16% and the green-veined white down 2%. It was, however, a much better year for the red admiral – up 78% on 2016 – and the comma – up 91% – with both of these species increasing over the long term.
The UK Butterfly Monitoring Scheme involves thousands of volunteers collecting data through the summer. Last year a record 2,693 sites were monitored across the UK.
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