Width of grassland linkages for the conservation of butterflies in South African afforested areas

Flight behaviours of 23 butterfly species were mapped to establish the effect of both pine afforestation and different-sized grassland linkages on localised butterfly movements. Blocks of pine trees caused most butterflies to change direction and move away from the pine edge. Only four species crossed the grassland/pine edge, and of these, only two flew farther than 20 m into the pine forest. The adjacent grassland/indigenous forest edge had a higher number of species, but very few of these entered the forest. Movement rates were significantly faster in the narrow and highly-disturbed linkages, than in the wide and open grasslands, with the linkages acting as conduits between the preferred grassland patches. However, only highly vagile and eurytopic species actually entered the narrower grassland linkages. In contrast, the wider linkages hosted a significantly higher species diversity and functioned as habitats per se and not just as movement corridors, with butterflies frequently stopping to nectar, oviposit, drink and sunbask. Knowledge of butterfly responses to different landscape structures has important conservation and management implications. From the results here, it is recommended that, for these butterflies, the natural grassland linkages should be wider than 250 m. (C) 2001 Elsevier Science Ltd. All rights reserved.