Natural grasslands and cereal fields play fundamental role in supporting biodiversity conservation and sustainable food production. Natural grasslands (including grasslands within a protected area and unprotected grasslands) and cereal fields provide multiple ecosystem services, but also involve significant trade-offs (e.g., food production vs. soil carbon sequestration). Yet, unlike aboveground plants and animals, the capacity of European protected areas to conserve plant and soil microbial diversity and ecosystem services in natural grasslands under global environmental changes is virtually unknown. Moreover, we know very little about how cereal fields will respond to multiple co-occurring global change stressors, such as drought, pesticides and over-fertilization, which are threatening the conservation of soil biodiversity and function as well as food production. Objectives 1 & 2 will evaluate whether protected areas promote soil biodiversity and multiple ecosystem services in European natural grasslands, and will monitor the microbial diversity and function in cereal fields. To such an end, we will conduct a European-level survey across grasslands’ triplets with different land use intensities (from protected and unprotected natural grasslands to maize and wheat fields). The sampling in cereal fields will support the monitoring that the Crop Microbiome Initiative started in these sites 3-5 years ago. In Objectives 3 & 4, GRASS4FUN will further investigate whether multiple global change stressors impact the microbiome and function of European natural grasslands and cereal fields. To do so, we will use combine the modelling and mapping of soil biodiversity and function across climate and land cover change scenarios with a manipulative study using microcosms subjected to multiple global change stressors. GRASS4FUN will be performed in close collaboration with a stakeholder advisory board to facilitate engagement and uptake by end-users, policy makers and society with the fundamental goal of providing ground-breaking knowledge to increase the resilience of grasslands to global stresses and protect European biodiversity, including organisms living in soils. GRASS4FUN will provide critical knowledge for the long-term economic benefits of the EU, and it is in line with multiple European-level programs such as Farm to Fork Strategy, EJP Soil and European Green Deal.