Is the Natura 2000 network sufficient for conservation of butterfly diversity? A case study in Slovenia

Abstract

Slovenia has one of the most extensive Natura 2000 networks in Europe with 259 SAC’s covering 31.4% of the country. To determine how well does the current network cover the areas of high butterfly diversity and/or aggregation of the butterfly species of conservation concern, the data from the recent survey for a distribution atlas were used. Altogether 99,423 records of 173 species collated after 1979 were used. The data distribution is slightly biased towards SAC’s, with 44.8% of localities within them, most likely due to sparsely sampled urban areas and intensive farmland areas which are found only outside SAC’s. The diversity and distribution of red listed species was evaluated at a 5 × 5 km grid square level. Additionally the importance of the size of the SAC’s was compared to their butterfly species diversity. In general the high diversity areas also hold the largest aggregation of red listed species with core areas concentrated in SW Slovenia. The SAC’s cover majority of areas with high diversity and the distribution of all but one threatened butterfly species. That species is Colias myrmidone, which is now considered extinct in Slovenia with no records after 1993. The most prominent areas with high conservation value in Slovenia not included in the SAC’s network are the Koroška region, Goriška Brda region, lower Sava River valley and Slovenske Gorice region. The butterfly diversity in small SAC’s is relatively high with increases in size only gradually increasing the species numbers, thus emphasizing the importance and conservation value of small SAC’s for sustaining high butterfly diversity in Slovenia.