European Lepidoptera: Numbers and Trends
Lepidoptera are scale-winged and almost exclusively phytophagous insects, representing a mega-diverse radiation, probably correlated with the great diversification of flowering plants since the Cretaceous (Menken et al. 2010). This major insect order has been divided traditionally into the day-flying butterflies and largely nocturnal moths. In Europe, the order currently contains close to 9900 recorded species (lepidoptera.pl), of which 482 species (i.e. ca. 5 %) are butterflies. About a third of these butterfly species have currently declining populations on a European scale, and 9 % are threatened (van Swaay et al. 2010). In some European regions these figures are far higher; in Flanders, for example, 19 out of 67 resident butterfly species (28 %) went extinct since the start of the twentieth century, whilst 25 species (37 %) are currently threatened (Maes et al. 2013). Such high proportions can be explained by cumulative effects of environmental pressures due to a long history of economic development (Dullinger et al. 2013). European-wide declines are especially worrisome since Lepidoptera provide many vital and economically important services within terrestrial ecosystems, such as nutrient cycling, prey resources and pollination. The European Red List for butterflies identifies the main drivers for these declines as habitat (connectivity) loss and degradation due to agricultural intensification and the invasion of shrubs and trees resulting from farmland abandonment (van Swaay et al. 2010).
Moth trends have not yet been evaluated at the European scale, although national trends are available for a handful of countries. For example, the very recent assessments in Britain and The Netherlands show a picture similar to butterflies. Across Britain, overall abundance of macro-moths declined by 28 % over a recent 40-year period, with total numbers having decreased by 40 % in the more populated southern half of Britain. Two-thirds of common and widespread macromoth species for which national population trends were calculated, decreased in abundance, with 61 species having declined by 75 % or more over 40 years (Fox et al. 2013). The preliminary Red List for macro-moths of The Netherlands (841 species) shows that 70 species (8 %) went extinct since the nineteenth Century and that 300 species (35 %) are currently threatened (Ellis et al. 2013). The decreasing extent of habitat and the degradation of its quality, more specifically via agricultural intensification, changing woodland management, urbanisation, climate change and light pollution, are likely causes of the observed changes in moth biodiversity (Fox et al. 2013).