British Butterflies in Freefall

Small tortoiseshell (c) Jim Asher/ Butterfly ConservationBBC Animal Science — The British butterfly population is continuing a marked downward trend. This is according to a national survey which revealed that numbers of the insects fell by more than 20% between 2010 and 2011.

The results, announced by the charity Butterfly Conservation, appear to contrast with a recent study revealing a boom in numbers of rare UK species. But while rare species may thrive in Britain’s “pollinator hot spots”, the more general outlook appears bleak. …

In July and August 2011, more than 500 volunteers counted butterflies on these patches of countryside. Each person counted an average of 47 butterflies and saw seven different species. This is a reduction of more than 20% in the number of butterflies per survey compared to 2010. It is also a 40% reduction compared with 2009, when each recorder saw an average of 80 butterflies and eight different species.

Butterfly Conservation has blamed the decline on “last year’s record-breaking cold summer”, but also said there was a long-term and “ongoing deterioration of suitable butterfly habitat across the countryside”.

The once ubiquitous small tortoiseshell was one of the species badly-affected, with less than one seen per kilometre walked, on average. Butterfly Conservation says that, less than a decade ago, this species was “likely to be seen in almost every garden and flowery place through the summer months”. (06/01/12)