Aim: Biodiversity loss is a major global challenge. While population trends of vertebrates are well documented, insect declines have not been sufficiently studied and their drivers are still not fully understood. This inhibits the implementation of sensible conservation action. Repeating historical surveys can help to reveal the patterns and drivers of insect declines.

Location: Central Europe

Time period: 2018 to 2020

Methods: We resurveyed 199 study sites in which Orthoptera assemblages had been recorded between 1986 and 1999.

Results: Our results show a significant increase in species per site (α-diversity), but simultaneously a homogenization of Orthoptera assemblages (decreasing Sorensen’s β-diversity). Highly mobile species significantly increased in site occupancy compared to species with low mobility. Some Orthoptera species showed significant altitudinal range shifts, including species with positive trends (i.e. expansion to higher altitudes) and negative trends (i.e. extinction at lower altitudes). Abandonment of extensively used grassland sites and the associated afforestation had negative effects on Orthoptera, underlining the importance of extensive grassland management. Protected areas had a high efficacy for conservation as trends in site occupancy were generally more positive in protected areas than in unprotected sites.

Main conclusions: Our results provide insights into the patterns and drivers of orthopteran assemblage turnover, including major effects of agricultural land use change and climate change. These results are essential for implementing or adapting conservation action, as they show that traditional land use practices and reduction of nitrogen input are important to preserve Orthoptera. Insect monitoring is crucial for understanding global and regional insect population trends and for preventing species extinctions. It is therefore critical to repeat historical surveys in order to understand global biodiversity change and implement the necessary actions.