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

Abstract

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.

Keywords: biodiversity; biodiversity–ecosystem services relationships; ecosystem function; ecosystem services; mechanisms; proxies.

Figure 1.

Schematic of the complex linkages (‘cascade’ [25]) involved in final ES delivery. The examples of ES, underlying ecosystem functions (EFs; also termed ‘intermediate services’ [24]), abiotic and societal factors represent a non-exhaustive selection.

Figure 2.

Representation of observed static species richness-based B–EF relationships. B–EF relationships can vary from linear to rapidly saturating, where high levels of ecosystem functioning occurs in the presence of few species [60,62]. Commonly observed saturating B–EF relationships show complementarity between species at low species richness (complementarity in niche partitioning resulting in increased overall resource use) driving increased functionality, while at higher levels of species richness many species may exhibit redundancy [,–64]. Note that static saturating curves do not imply actual functional redundancy in some species; temporal heterogeneity increases the insurance value of biodiversity through time [–65].

Figure 3.

Hypothetical variation in B–EF–ES relationships (see also [18]) as driven by the main contributing EFs (within an EF portfolio). Black arrows refer to positive effects (dashed arrows displaying less strong effects) while grey arrows refer to negative effects.