Selecting cost effective and policy-relevant biological indicators for European monitoring of soil biodiversity and ecosystem function

Introduction – There is a demand for reliable tools to design and implement strategies for sustainable management of soils, including the design of policy-relevant and cost-effective indicators for monitoring soil biodiversity and ecosystem function. Our goal, which forms part of an EU-funded project called EcoFINDERS, was to develop and evaluate novel approaches for monitoring of soil biodiversity and functioning across a broad range of European environments and land-use systems. Methods – Eighteen existing and potential biological indicators were selected using a logical sieve approach, combined with meta-analysis of European soil monitoring schemes. All indicators were evaluated at six, long-term field sites offering replicated plots of different agricultural management scenarios. The sites covered the major European climatic zones and land use types, while the replicated treatments spanned a wide range of management intensification. Soil sampling was standardised and coordinated across all sites. Results – The response of the indicators was analysed with respect to the intensity gradient of applied treatments. All the indicators tested were sensitive between the different sites, but showed variable sensitivity to the imposed management practices. Preliminary analysis showed greater effects of intensification on biodiversity and function in arable than grassland systems.. Cost-effectiveness of the indicators was assessed from their labour intensity, practicability and ease of interpretation. Conclusion – Results clearly demonstrated strengths and weaknesses to each type of indicator, confirming that no single indicator will be appropriate for a large scale monitoring scheme. A scheme should aim for the lowest number of indicators in order to be efficient with limited resources, but with enough power to address the specific question. Some of the developing methods, especially next-generation sequencing and functional gene analysis, look increasingly favourable from cost-effective and ease of interpretation perspectives. The ‘toolkit’ of biological indicators can be adapted according to the priorities of the monitoring scheme. Keywords: Monitoring, Indicators, Land use intensity, Sustainability