Butterflies Crash In Fourth Worst Year On Record
12 April 2017
UK butterflies suffered their fourth worst
year on record in 2016 with the majority of species experiencing a
decline in numbers, a study has revealed. A mild winter followed by
a cold spring contributed to conditions that saw both rare and
widespread species struggle despite many parts of the UK enjoying a
warm and dry summer. Some 40 of the 57 species studied
recorded a decline compared with 2015, the annual UK Butterfly
Monitoring Scheme (UKBMS) led by Butterfly Conservation, the Centre
for Ecology & Hydrology (CEH), British Trust for Ornithology
(BTO) and Joint Nature Conservation Committee (JNCC) revealed.
The highly threatened Heath Fritillary had its
worst year on record for the second year running, while the
Grizzled Skipper, Wall, Grayling, White-letter Hairstreak and White
Admiral all recorded their worst ever years. The Heath
Fritillary, restricted to just a handful of sites in southern
England, saw numbers slump by 27% compared to 2015. This ongoing
decline raises fears for the long-term future of the butterfly
whose numbers have fallen by 82% in the last decade.
The rare Grizzled Skipper, found in southern
England and parts of Wales, saw numbers tumble by 24%. The
butterfly is a spring-flying species emerging from April, a month
that was around a degree colder than the long-term average in
2016. The Grizzled Skipper’s struggles mirrored a bad year
overall for the skippers with all but one of the UK’s eight species
suffering a fall in numbers compared to 2015.
The White Admiral, White-letter Hairstreak and
Grayling slumped by 59%, 42% and 27% respectively while more
widespread species also struggled with the Wall down 31%, the
Gatekeeper down 48% and Meadow Brown falling by 31% compared with
2015. Research suggests that the UK’s increasingly mild
winters are having a negative effect on butterflies as they may
lead to increased disease, predation or disruption of overwintering
Cold springs can also cause problems for
butterflies by reducing or delaying emergence leading to shortened
lifespans. Some species bucked the trend to record reasonable
years. The previously extinct Large Blue, one of the UK’s rarest
butterflies, recorded its second best year on record with numbers
up 38% on 2015.
The butterfly has responded to conservation
work to improve the specific grassland habitat that it relies upon
to thrive and has showed a significantly increasing population
trend since its reintroduction in 1983. The widespread and
migratory Red Admiral recorded a rise of 86% compared to 2015 and
the Clouded Yellow, another mainly migrant species, saw its numbers
rise by 35%.
Anna Robinson, Monitoring Ecologist at JNCC
said: “We are really grateful to the thousands of volunteers who
get involved in monitoring the UK’s butterflies.
“The evidence provided by the UKBMS is of
great importance in showing the need for conservation action to
improve the situation.”
The UKBMS has run since 1976 and involves
thousands of volunteers collecting data through the summer. Last
year a record 2,507 sites were monitored across the UK. The scheme
is organised and funded by Butterfly Conservation, the Centre for
Ecology & Hydrology, the British Trust for Ornithology and the
Joint Nature Conservation Committee.
Summary of Changes table for the UK.
Full UKBMS Press Release