The quest for a mechanistic understanding of biodiversity-ecosystem services relationships

Ecosystem services (ES) approaches to biodiversity conservation are currently high on the ecological research and policy agendas. However, despite a wealth of studies into biodiversity's role in maintaining ES (B-ES relationships) across landscapes, we still lack generalities in the nature and strengths of these linkages. Reasons for this are manifold, but can largely be attributed to (i) a lack of adherence to definitions and thus a confusion between final ES and the ecosystem functions (EFs) underpinning them, (ii) a focus on uninformative biodiversity indices and singular hypotheses and (iii) top-down analyses across large spatial scales and overlooking of context-dependency. The biodiversity-ecosystem functioning (B-EF) field provides an alternate context for examining biodiversity's mechanistic role in shaping ES, focusing on species' characteristics that may drive EFs via multiple mechanisms across contexts. Despite acknowledgements of a need for B-ES research to look towards underlying B-EF linkages, the connections between these areas of research remains weak. With this review, we pull together recent B-EF findings to identify key areas for future developments in B-ES research. We highlight a means by which B-ES research may begin to identify how and when multiple underlying B-EF relationships may scale to final ES delivery and trade-offs.