Butterflies threatened by increasingly extreme weather

The impact of climatic extremes might pose a threat to Britain's butterfly populations, according to a study published Monday in the Journal of Animal Ecology.

The occurrence of extreme weather events, including heatwaves, heavy rainfall and droughts, has become more frequent in recent years due to climate change.

A team led by researchers from the University of East Anglia (UEA) used data from the UK Butterfly Monitoring Scheme to analyze the effect of extreme weather events on the population change of local butterfly. The data was collected from over 1,800 sites across Britain, spanning 37 years.

The researchers found that extremes of temperature could significantly influence butterfly populations. Extreme heat during the "overwintering" life stage of butterflies was "the most detrimental extreme weather event affecting over half of UK species," said one of the study authors, Dr Aldina Franco, at UEA.

"This may be due to increased incidences of disease or potentially extreme hot temperatures acting as a cue for butterflies or their larvae to come out from overwintering too early and subsequently killed off by temperatures returning to colder conditions," explained Dr Franco.

Precipitation during cocoon life-stage of butterflies also caused negative effects on over one quarter of the species, according to the researchers.

Meanwhile, the study showed that extreme weather events might not always be bad for butterflies. Their adult stage could benefit from extreme heat.

"This is not an unexpected finding given that butterflies are warm loving creatures. Years with extreme warm summers and winters may have mixed effects, " said Dr Franco.