Butterflies bounce back to best year in over two decades

UK butterflies bounced back in 2019, thanks to last year’s unusually warm and wet summer.

Marbled White butterfly Picture: Bob Eade, Butterfly Conservation

In their best year since 1997, just over half of species showed higher population levels over 2018.

Experts say the encouraging results "provide evidence that the overall rate of decline of butterflies is slowing and for some species (is) being reversed."

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Professor Tom Brereton, Associate Director of Monitoring and Research at Butterfly Conservation said positive conservation through agri-environment schemes, increased woodland cover, climate warming, increases in grazing levels by wild animals and a slowing in the rate of agricultural intensification were all factors.

Dark Green Fritillary Picture:Gary Faulkner, Butterfly Conservation

It was also the eighth best year for butterflies since the annual UK Butterfly Monitoring Scheme started in 1976.

Prof Brereton said: “We’re really heartened to see a shift in the fortunes of many of our most loved species.

"Encouragingly a number of Priority Species such as Adonis Blue, Brown Hairstreak, Dingy Skipper, Large Heath, Marsh Fritillary, Silver-studded Blue, Small Blue and the Silver-spotted Skipper that have been the focus of intensive conservation efforts in recent decades by Butterfly Conservation and partners are no longer in long-term population decline.

“The long-term situation for butterflies in general does remain a cause of concern though, with more species declining than increasing since the 1970s.”

The Marbled White had its best year in the series with annual abundance up by 66%, Ringlet (second best year in the series, up by 23%), Dark Green Fritillary (third best year, up 51%), and Meadow Brown (fifth best, up 38%).

The rare Lulworth Skipper, restricted to the Dorset coast which has been in free fall in recent years rallied with its annual abundance up by a whopping 138%.

However the Common Blue dropped by 54%, Adonis Blue by 40%, Green-veined White by 43% and Large White by 40% ,with all four species having below average years.

Of particular concern is the rare Heath Fritillary, which is restricted to a tiny number of sites in southern England. This butterfly saw its annual abundance drop by 34%.

Migrant butterflies also had a bumper year with Red Admiral numbers up 195% and Painted Lady numbers up by a massive 1993%.

A "Painted Lady summer", where millions of the butterflies arrive en masse, happens around once every 10 years the UK.

The UKBMS involves thousands of volunteers collecting data through the summer. Last year a record 3,014 sites were monitored across the UK.

It is led by Butterfly Conservation, the UK Centre for Ecology & Hydrology, British Trust for Ornithology and Joint Nature Conservation Committee.