Does extensive grazing benefit butterflies in coastal dunes?

Grazing at low stocking rates has become a common management practice in nature restoration projects in the Netherlands. However, detailed knowledge of grazing impact is often poor, in particular for invertebrates. This study addressed the impact of extensive grazing on butterflies. Butterflies are critical indicators of habitat quality for many plant and animal species. We compared monitoring data from 1992 to 1996 for calcareous coastal dune areas in the Netherlands with different management: 11 grazed areas, 7 ungrazed areas and 4 areas managed by annual cutting. Grazing typically concerned year-round grazing by cattle and/or ponies, at low stocking rates (0.05-0.26 head ha(-1) yr(-1)). Butterfly abundance was related to species composition and structure of the vegetation. Changes in butterfly abundance were positive in grazed and ungrazed areas compared to cut areas. Species richness was not affected by management, but individual species differed in their response. Species from open grassland benefited most from grazing, particularly Issoria lathonia (Queen of Spain Fritillary) and Lycaena phlaeas (Small Copper). No clear negative effects of grazing were observed, but species occurrence was not always positively related to the environmental characteristics associated with grazing. In the long run, even lower stocking rates might prove more beneficial to the butterfly community as a whole. Four of the more frequently observed species, I. lathonia, Hipparchia semele (Grayling), Pyrgus malvae (Grizzled Skipper) and Aricia agestis (Brown Argus), are listed as threatened to susceptible in the Netherlands. All were apparently favored by grazing. It is concluded that extensive grazing has good potential to enhance butterfly diversity in restoration projects.