Butterflies are a priority in Purbeck

Adonis Blue butterfly

Loss of habitat means that three-quarters of Britain’s butterflies are in decline. And even Purbeck’s famous chalk ridge is affected.

Butterflies thrill us for reasons we can’t entirely explain.  They retain their ethereal mystery and we value them all the more for it. The problem is, we’ve had a funny way of showing it lately.       

Pesticides, ploughing up hay meadows, planting conifers over moors and heaths, taking the cattle off our chalk downs have all had a serious effect on butterfly numbers since the Second World War.  Loss of important habitats means that three-quarters are now in decline, including some of Purbeck’s most treasured. 

Purbeck’s famous chalk ridge, stretching from Lulworth Cove in the east to Old Harry Rocks in the west, is one of the few places in Britain where the sight of a Lulworth Skipper can light up your day. Small and brown, it is a modest celebrity, more than can be said for its showily iridescent friend the Adonis Blue. These contrasting marvels share Purbeck’s delicious coastal air with 23 other equally diverse butterfly species, but these Skippers, Blues, Whites, Coppers, Hairstreaks and Fritillaries are a vulnerable bunch. 

Take a walk to Old Harry Rocks
Old Harry Rocks at Studland Beach
Take a walk to Old Harry Rocks

A butterfly super highway

Once upon a time, this wild and calcareous grassland ridge would have been wildflower-rich and boundary free, a 15 miles long butterfly super highway. Today, it’s more a succession of road blocks, lane closures and diversions. In too many areas, cattle no longer graze the sloping grassland and gorse scrub has taken over. Elsewhere, fertilizers have turned these species-rich grasslands a brighter but botanically far duller, shade of green.  The wild flowers are the foodplants for the highly specialised caterpillars but the butterfly hotspots have become smaller, more fragmented.   The remaining populations of these rare and special creatures have become isolated and vulnerable. 

The National Trust in Purbeck has begun working with its neighbours to free it all up again and give the butterflies back their non-stop wildlife corridor. Gorse is being cleared, and they are working with tenant farmers to see how to restore the low-input, traditional grassland grazing that made this ridge so special in the first place.  

Butterflies and moths are widely recognised as indicators of a healthy environment so as the habitats start to connect again, the future is looking brighter.  

Additional facts 

  • The Purbeck Ridge, built of almost vertical chalk, forms part of a monocline or upfold produced by earth movements nearly twenty million years ago. 
  • Look east from Purbeck’s chalk ridge behind Studland and you can clearly see its continuation, separated now by sea, on the Isle of Wight 
  • The Lulworth Skipper only flies in July and August 
  • There are two annual broods of Adonis Blue, in early and late summer. 
  • Other rare and notable Purbeck Ridge species include invertebrates such as the Grey Bush Cricket and Large Chrysalis Snail. 
  • Butterflies are the most threatened wildlife group in Britain.