Linking key performance indicators to insect abundance in agricultural grasslands: Effects of plant diversity, farming intensity, soil type and landscape characteristics

As the largest land user in the Netherlands, the dairy sector has a significant impact on the habitats of flora and fauna within and around agricultural landscapes. To address this, the Sustainable Dairy Chain has implemented the Biodiversity monitor, which uses Key Performance Indicators (KPIs) to quantify biodiversity performance at the farm level. The aim of our research was to gain a comprehensive understanding of how dairy farming and grassland management affect insect abundance, in relation to soil type and the surrounding landscape. These insights were then used to evaluate the effectiveness of KPIs in the Biodiversity Monitor. We investigated the effects of plant diversity (regular vs diverse grasslands), farming intensity (three classes based on milk production per hectare) and soil type (clay, sand and peat) and landscape characteristics on insect abundance in grasslands on 36 dairy farms in The Netherlands, using sticky traps. We found that the effect of nitrogen fertilization, as an indicator of land-use intensity, on insect abundance was body size dependent. Large insects (>4 mm) were negatively influenced by nitrogen fertilization, while small insects (<4 mm) were positively influenced. The abundance of insects <4 mm was best explained by factors operating at the field level, whereas differences in abundance of insects >4 mm were best explained by soil type and landscape characteristics, factors operating at the landscape level. Our findings highlight the need to strengthen KPIs by incorporating measures that reduce land-use intensity and enhance landscape diversity to more effectively support biodiversity in agricultural areas.