Developing biodiversity indicators for monitoring agricultural sustainability: Insights from a Delphi expert process

With agricultural activities widely cited as drivers of biodiversity loss globally, it is important to distinguish between agricultural practices that have negative impacts and those with positive impacts on biodiversity. To measure on-farm biodiversity outcomes, the direction and magnitude of impacts need to be assessed. Outcomes can be measured using indicators. However, there is currently a multitude of biodiversity indicators available. This abundance makes monitoring biodiversity outcomes challenging, as farmers lack clarity on what to measure. This study presents a shortlist of biodiversity indicators selected via an expert panel as part of a modified Delphi process. The modified Delphi implemented two scoring approaches across four rounds, exploring the decision-making behind indicator selection. Thirty-nine experts scored 58 indicators based on their appropriateness for evaluating on-farm biodiversity and the practicality of data collection by non-specialists. The variation in scoring approaches helped combat respondent fatigue and build robustness into the indicator selection process. At the end of the study, nine indicators were chosen for monitoring on-farm biodiversity: area of habitat types, a connectivity index, a diversity index (landscape), both a crop and livestock diversity index, in-field crop temporal heterogeneity, indicator species, species richness, and species rarity. A final step considering each indicator's ability to inform on-farm decision-making is likely to have increased the efficacy of the chosen indicators in driving practice change. This would ensure the selected indicators are multifunctional, providing an evaluation of impact while also highlighting the desired direction of travel for the farmer or landowner.