Feasibility and reliability of farmer-recorded plant diversity indicators in European grasslands

European grasslands are biodiversity hotspots but face ongoing threats from intensification and abandonment. Monitoring is essential for evaluating policies that promote grassland biodiversity, but conventional expert-led surveys are costly and difficult to scale. Farmer-led biodiversity recording offers a potential solution, but its feasibility and reliability remain uncertain. This study aimed to assess whether farmer-recorded indicators can provide reliable and practical measures of grassland plant diversity that could support broader biodiversity monitoring and assessment of public goods delivery. We firstly reviewed 14 European monitoring case study schemes, supplemented by stakeholder interviews in eight of these schemes. Secondly, we compared simple farmer-recorded indicators at the field and farm system levels with expert botanical assessments across 26 low-intensity farms in the UK, Sweden, and Romania. Analysis of case study monitoring schemes revealed that limited time and technical expertise were major barriers to farmer participation, while adequate incentives, scheme simplicity, and supportive technology acted as key enablers alongside the well-documented need for training and support. Comparisons with botanical assessments showed that simple farmer-recorded measures, particularly forb species counts, were strong proxies for plant species richness and diversity, while some abundance-based measures such as vegetation cover estimates also showed significant relationships with botanist assessments. In contrast, farmer-recorded indicator species performed poorly, likely due to short indicator species lists and the lack of farmer training. Farm system metrics were also weak predictors of species richness and diversity, although they may be informative across broader gradients of management intensity. Overall, our findings demonstrate that farmer-led biodiversity recording is feasible when based on straightforward, observable indicators, combined with adequate motivation. These approaches could complement expert assessments in supporting biodiversity goals and results-based agri-environment schemes.