Small Tortoiseshell - Rob Blanken

Butterfly numbers in the UK countryside fell by almost a quarter last summer, according to a new scientific study.

The Wider Countryside Butterfly Survey (WCBS) revealed that butterflies suffered a disappointing 2011 compared to 2010 with recorders seeing 22% fewer butterflies on average.

Last year's record-breaking cold summer and the ongoing deterioration of suitable butterfly habitat across the countryside are seen as causes for the fall in numbers.

Garden favourite the Small Tortoiseshell was one of the species badly affected, with less than one seen per kilometre walked on average in the countryside.

Such low numbers are a cause for concern given that less than a decade ago the butterfly was likely to be seen in almost every garden and flowery place through the summer months.

The drop in Small Tortoiseshell sightings from the WCBS mirrors an alarming and ongoing decline for this once ubiquitous species. This is the first time that a comprehensive survey has shown how few are now found across the countryside as a whole.

The WCBS involves counting butterflies in more than 700 randomly generated 1km-squares across the UK countryside.

The scheme helps assess the health of butterfly populations across the wider countryside, rather than specially managed hotspots such as nature reserves.

Last year, recorders saw on average 47 butterflies from seven species per-survey made over July and August.

This represents a 22% reduction in numbers from 2010 and an alarming 41% reduction from 2009 when recorders saw an average of 80 butterflies and eight species.

There were 43 visits where were recorders saw no butterflies at all - double the 2010 figure.

The Common Blue also struggled in 2011; the butterfly was present in only one-third of squares compared to over half in 2010.

The Wall declined in distribution for the third consecutive year with this once common species now largely absent from central England.

The Meadow Brown was the most widespread and abundant species, being found in more than 80% of squares.

WCBS Co-ordinator Dr Zoë Randle said: "The new survey is proving vital in getting better information on how our common butterflies are faring across the countryside as a whole.

"The gloomy results show we need to step up efforts to rebuild a better countryside for butterflies."

Kate Risely, Breeding Bird Survey Organiser at the BTO added: "It is important to carefully monitor the numbers of our wider countryside butterfly species in order to detect potential threats to their populations.

"Results from the upcoming 2012 survey and in years to come will show whether these declines are sustained. We're very pleased that bird surveyors can contribute to butterfly recording, highlighting the value of dedicated naturalists in our society."

The WCBS is run by Butterfly Conservation, the British Trust for Ornithology (BTO) and the NERC Centre for Ecology & Hydrology (CEH) as part of the United Kingdom Butterfly Monitoring scheme (UKBMS).