Diachronic variations in the distribution of butterflies and dragonflies linked to recent habitat changes in Western Europe

Abstract

In the context of ongoing global changes, it is crucial to characterise and understand the species distribution dynamics. Despite increasing emphasis on insects’ conservation issues, evidence of distribution changes in insects over a wide range of bioclimatic conditions remains scarce in Western Europe. We examined distribution changes in butterflies and dragonflies in three European countries over 34 years, determined the influence of environmental changes, especially land cover, and assessed how of species ecology related to distinct responses. We analysed the diachronic variations by compiling occurrence data in France, Belgium, and Luxembourg for 240 butterfly and 95 dragonfly taxa. We found contrasting patterns of diachronic variation in butterfly and dragonfly distributions, i.e. a strong gradient of disappearance for butterflies (from northwest to southeast with significantly higher rate of disappearance in urbanised and intensive agriculture areas of north-western France), whereas dragonflies showed lower and heterogeneous variation in occurrences, mainly related to alteration and regression of aquatic habitats. Species responses appeared closely linked to their ecological preferences, with greater decline in habitat specialist species. Butterfly and dragonfly species are constrained by their dependence to host plant species and to aquatic habitats, respectively, and proved to convey complementary insights on the influence of environmental changes in biodiversity dynamics. Conservation priorities were identified across species and administrative units, revealing that almost 80% of the declining taxa were not listed on the current protection lists. Our results support the need to update current French policies in terms of insect conservation.