Heatwave hit UK butterfly populations, study confirms
Purple emporer numbers were strong in 2022, but may be reduced this year when the next generation emerges.
New data from the UK Butterfly Monitoring Scheme (UKBMS) found that the heatwave during the summer of 2022 caused a reduction in the abundance of some UK butterflies.
During the spring and early summer of 2022, average and above numbers were reported of species such as the green-veined white, small white, small tortoiseshell, peacock and brimstone.
However, following draught conditions that killed plants which caterpillars use for food, the numbers were much reduced later in the year.
This decline is expected to continue into 2023 and could be especially noticeable in species that only have one generation in a year. Species such as the purple emperor, large blue, chequered skipper and dark green fritillary were abundant in 2022, but it is yet to be seen how their numbers will be affected this summer when the next generation emerges.
Draughts have previously affected butterfly populations in 1976 and 1995, according to UKBMS data. Some species have never fully recovered from the 1976 draught, although habitat reduction may well have played a major role in preventing a return to their former abundance.
Eighty per cent of butterfly species have declined in numbers since the 1970s, according to Butterfly Conservation’s State of the UK’s Butterflies report.
The annual UKBMS survey is led by Butterfly Conservation, the UK Centre for Ecology & Hydrology (UKCEH), British Trust for Ornithology (BTO) and Joint Nature Conservation Committee (JNCC). It monitors the natural annual fluctuations in butterfly populations as well as tracking long-term trends.
Dr Marc Botham, butterfly ecologist at UKCEH, said: “In 2022 we collected data from over 3,000 sites and we are incredibly grateful to the thousands of volunteers who carry out monitoring and maintain this invaluable long-term dataset. This enables scientists to measure how butterflies are faring as well as assessing the health of our countryside generally. The UKBMS data are vital in assessing the effectiveness of government policies and progress towards the UK’s biodiversity targets.”
Trudy Harrison, minister for natural environment and land use, said: “Our beautiful butterflies are at risk from a changing climate and human activity. We have set out clear steps to enable nature’s recovery through our Environmental Improvement Plan and Pollinator Action Plan, which will help us meet our legal target to halt the decline in nature by 2030.
“The impacts of warm and dry weather last year are cause for concern, but it is encouraging that the last decade has seen most species stabilise. In particular, I welcome the findings that the large blue and the purple emperor, two wonderful and unique species people may recognise from Wild Isles, both experienced their second best year on record in 2022.”
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