Can open access weeds occurrences across the European Union become a proxy for agricultural intensification?

Diverse communities of arable plants contribute to the long-term sustainability of agroecosystems and support a large variety of ecosystem services. Agricultural intensification influences the composition and structure of these communities and is one of the major drivers of biodiversity loss in Europe. Several European Union (EU) policies seek to reverse agroecosystems degradation and need biodiversity data-based indicators. Here we focus on arable fields with crops and arable plants. Open access to biodiversity data, such as through the Global Biodiversity Information Facility (GBIF), opens multiple options to develop large-scale indicators. We investigate whether occurrences of certain weeds from GBIF could become indicators of lower levels of agricultural intensification. For this, we designed an EU-scale data-driven proof of concept, using a 2018 EU28-wide 10 m resolution map of maize and a total of 2,082,796 occurrences data for 156 weed species associated to this crop. A total of 12 arable plants sensitive to intensification were identified that could possibly become indicators. We also show how GBIF data is able to capture the effect of proxies for agricultural intensification on plant communities associated with crops. Even with the limitations of studying only one crop for a single year, we present some of the potential of these data to assess the condition of agroecosystems. Novel integration of biodiversity relevant observations across scales will need to underpin the characterization of agroecosystems to inform farm, as well as landscape management and policy impact evaluation.