Effects of mire type, land use and climate on a strongly declining wetland butterfly

Abstract

Mires are characterised by highly specialised and threatened wildlife. One of these mire specialists that has severely declined is the Large Heath (Coenonympha tullia). However, detailed studies concerning the reasons for the dramatic population loss in central Europe are missing so far. In this paper: (1) we analyse the habitat preferences of adult C. tullia and oviposition site selection with respect to mire type and land use in one of the last German strongholds, and (2) we attempt to disentangle the impacts of land use and climate change on the decline of C. tullia on a national scale across Germany. Abundance of adult C. tullia was clearly affected by mire type and land use. It was highest on managed calcareous fens and lowest on unmanaged transition and raised bogs. The oviposition pattern of C. tullia females was best explained by (1) quantity of potential host plants (Eriophorum latifolium), (2) vegetation structure, and (3) microclimate. In Germany, C. tullia populations have become extinct in lowlands with a mild and relatively dry climate while most colonies in wet and cold mountain areas have survived. However, there is evidence that habitat loss and habitat deterioration, rather than climate change, are the drivers of the range retraction. To create low-growing vegetation rich in E. latifolium, traditional mowing late in the year and light grazing seem to be suitable management tools. In addition, conservation management should aim to maintain high water levels or restore them, especially to counteract effects of climate change in the future.