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Extreme weather threatens butterflies

AAP logoAAP 31/10/2016 John von Radowitz

Britain's butterflies could be under threat from increasingly frequent episodes of extreme weather.

Heat waves, cold snaps, and heavy rain may have already contributed to reported butterfly population crashes, scientists say.

While it is well known that changes to overall climate can affect ecosystems, much less is understood about the impact of short-term spells of harsh weather known as extreme climatic events (ECEs).

Researchers analysed data from the UK Butterfly Monitoring Scheme (UKBMS), which contains information on butterfly populations collected from more than 1,800 sites across the UK over 37 years.

The team found that rainfall level during the cocoon life stage of butterflies adversely affected more than a quarter of butterfly species in the UK.

But the greatest harm was caused by extreme heat during the "over-wintering" life stage, which had an impact on more than half the species.

Study co-author Dr Aldina Franco, from the University of East Anglia, said: "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 over-wintering too early and subsequently (be) killed off by temperatures returning to colder conditions."

Hot weather was found to benefit warmth-loving adult butterflies, leading to a positive population change in more than a third of species.

However, on balance the bad effects of extreme weather events outweighed the good, said the scientists whose findings are published in The Journal Of Animal Ecology.

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