Communities of butterflies on ten spoil heaps in Ostrava Basin

Heaps, dumps of mining waste, metallurgical slags, and other materials are a very characteristic type of post-industrial sites in the Ostrava Basin. Many studies in the past few decades have focused on plants, fungi, spiders, and beetles inhabiting this unique habitat, revealing many rare species. Yet, comprehensive research on butterflies, an emblematic group of insects, has been surprisingly lacking. This study aimed to assess the diversity and distribution of butterflies on these heaps employing a consistent methodology and data collection approach conducted by the same team throughout the entire season. The purpose of our research was to assess whether heaps in the Ostrava Basin could serve as refuges and alternative habitats for certain rare butterfly species. Through our comprehensive study, we aimed to evaluate the potential of these heaps to support biodiversity and conserve endangered lepidopteran species within the region. Ten heaps were selected based on their accessibility, biological significance, and habitat predispositions. Butterfly surveys were conducted from May to September 2023 using nets. During the research, a total of 59 species of butterflies were recorded, of which 37 were diurnal butterflies, the main group under study. Four of these species were listed on the Red List of the Czech Republic or were subject to legal protection. In addition to diurnal butterflies, heaps provide an alternative habitat for many other notable invertebrate and vertebrate species. Emphasizing the importance of heaps as vital habitats for biodiversity, particularly for protected and endangered species, the research demonstrates that heaps in Ostrava Basin can serve as refuges and alternative habitats for various species of organisms that would otherwise be threatened, including some butterfly species.