2012 worst year ever for butterflies Many of our most threatened butterflies were already in a state of long-term decline prior to the 2012 deluge. There are now real fears that these already struggling species could become extinct in some parts of the UK as a result of last year's wet weather. The critically endangered High Brown Fritillary fell by 46 per cent, the vulnerable Marsh Fritillary was down 71 per cent and the endangered Heath Fritillary saw its population plummet by 50 per cent in comparison to 2011. Hairstreaks did particularly badly last year - the Black Hairstreak, one of the UK's rarest species, saw its population fall by 98 per cent. The Green Hairstreak was down 68 per cent, the White-letter Hairstreak fell by 72 per cent and the Brown Hairstreak, slipped by 34 per cent. Many common species also struggled. The Common Blue plummeted by 60 per cent, the Brown Argus collapsed by 73 per cent and the Large Skipper fell by 55 per cent. The widespread "Whites" including Green-Veined White and the two 'Cabbage Whites', Large White and Small White saw their populations tumble by more than 50 per cent. The Orange-tip fell by 34 per cent. The alarming slide of garden favourite the Small Tortoiseshell continued with its population slipping 37 per cent from 2011 figures. Data was gathered by the UK Butterfly Monitoring Scheme (UKBMS) jointly led by Butterfly Conservation and the Centre for Ecology & Hydrology (CEH). Only four species saw their populations increase. The grass-feeding Meadow Brown was up 21 per cent and the Scotch Argus, which thrives in damp conditions, rose by 55 per cent. Dr Tom Brereton, Head of Monitoring at Butterfly Conservation, said some species will go extinct in certain areas Butterflies have proved before that given favourable conditions and the availability of suitable habitat they can recover, but with numbers in almost three-quarters of UK species at a historically low ebb any tangible recovery will be more difficult than ever.