The summer of 2019 provided a welcome boost to butterfly populations, according to the latest annual results.
The analysis comes from the annual UK Butterfly Monitoring Scheme (UKBMS), which is led by Butterfly Conservation, the UK Centre for Ecology & Hydrology (UKCEH), British Trust for Ornithology (BTO) and Joint Nature Conservation Committee (JNCC).
In their best year since 1997, just over half of UK butterfly species showed higher population levels in 2019 compared with 2018, making it the eighth best year since UKBMS was formed in 1976.
A warm spring and then a warm and wet summer last year provided good conditions for many butterflies.
Summer-flying species that benefited include the Marbled White, which had its best year since the records began in 1976, with annual abundance up by 66 per cent in 2019 compared to the previous year. Also enjoying an increase in numbers were the Dark Green Fritilary (up 51 per cent), Meadow Brown (up 38 per cent) and Ringlet (up 23 per cent).
A wide range of species benefited from a couple of warm summers in succession - Dr Marc Botham
However, some species did poorly in 2019 including the Common Blue, whose annual abundance fell by 54 per cent in a below-average year for this species, while numbers of the Adonis Blue, Green-veined White and Large White all decreased by around 40 per cent.
A number of spring-flying species did particularly well in 2019 including Chequered Skipper (up 175 per cent), Orange-tip (up 63 per cent) and Brimstone (up 32 per cent), all of which had their best year on record.
Dr Marc Botham, Butterfly Ecologist at the UK Centre for Ecology & Hydrology, says: “The analysis shows that numbers of a wide range of species benefited from a couple of warm summers in succession. In addition to record numbers of spring species such as Orange-tip and Brimstone, it was also encouraging to see annual increases in garden favourites such as Peacock and Small Tortoiseshell, both of which have had some poor years recently.
“Despite this, some wider countryside species such as Wall and Small Skipper remain at low levels compared to what they used to be.”
Dr Botham thanked the thousands of volunteers who gather data on butterflies every year at more than 3,000 sites across the UK.
Professor Tom Brereton of Butterfly Conservation points out that in addition to favourable weather conditions for butterflies, better habitats - thanks to agri-environment schemes and increased woodland cover - have also helped boost numbers. He says it is encouraging that several priority species that have been the focus of intensive conservation efforts in recent decades are no longer in long-term population decline, including Brown Hairstreak and Marsh Fritillary.
But Professor Brereton adds: “The long-term situation for butterflies in general does remain a cause of concern though, with more species declining than increasing since the 1970s.”