A Grid-Based Sampling Approach to Insect Biodiversity Monitoring in Agricultural Landscapes

Reports on recent declines in insect biodiversity have prompted discussions on how to assess insect species numbers across a wide range of different habitats and on large spatial scales. Previous approaches were often restricted to particular habitat types (such as calcareous grasslands) or taxa (such as butterflies). Here, we show that setting up insect traps along regular sampling grids (25 grid cells) in replicate 1 × 1 km landscapes allows sampling insect biodiversity across all habitat types in changing landscapes and for a wide range of taxa and functional groups, including herbivores, predators and pollinators. If combined with remote sensing and image classification workflows, our approach allows powerful conclusions on inter- and intra-annual dynamics of insects in agricultural landscapes that are often highly dynamic due to crop rotations. The number of samples obtained in each habitat closely follows the landscape-wide amount of each habitat type. Hence, the sampling scheme is suitable to compare insect populations and communities in different habitats according to the true habitat amount. Our approach complements the existing approaches of how landscape structure affects populations in a given habitat and is useful for long-term biodiversity monitoring.