Negative long-term effects of changed water availability on auchenorrhynchan communities in dry grassland reserves

Insect decline has been documented in an increasing number of studies, but attribution to potential drivers remains challenging. Climate change poses threats to insect biodiversity, and there is still little data on how climate change is already affecting insect communities. We present a resampling study on long-term trends in leafhopper and planthopper communities of dry grassland reserves in Germany, comparing samples from three sampling decades: 1960s, 2000s and 2010s. Diversity and abundance data were related to weather data and to information on conservation management. Insect communities changed significantly with respect to decade, season and seasonal precipitation but not with respect to mean seasonal temperature. Conservation management had limited effect. Specifically, wetter conditions resulted in significantly higher abundance and richness of insect communities. We infer that apparent decline of water availability in dry grasslands - among other drivers on landscape-level - plays a significant role in shaping communities of phytophagous insects in Central European cultural landscapes. Conservation management has to be adjusted to this development.