Predicting ecosystem vulnerability to biodiversity loss from community composition

Abstract

Ecosystems vary widely in their responses to biodiversity change, with some losing function dramatically while others are highly resilient. However, generalizations about how species- and community-level properties determine these divergent ecosystem responses have been elusive because potential sources of variation (e.g., trophic structure, compensation, functional trait diversity) are rarely evaluated in conjunction. Ecosystem vulnerability, or the likely change in ecosystem function following biodiversity change, is influenced by two types of species traits: response traits that determine species' individual sensitivities to environmental change, and effect traits that determine a species' contribution to ecosystem function. Here we extend the response-effect trait framework to quantify ecosystem vulnerability and show how trophic structure, within-trait variance, and among-trait covariance affect ecosystem vulnerability by linking extinction order and functional compensation. Using in silico trait-based simulations we found that ecosystem vulnerability increased when response and effect traits positively covaried, but this increase was attenuated by decreasing trait variance. Contrary to expectations, in these communities, both functional diversity and trophic structure increased ecosystem vulnerability. In contrast, ecosystem functions were resilient when response and effect traits covaried negatively, and variance had a positive effect on resiliency. Our results suggest that although biodiversity loss is often associated with decreases in ecosystem functions, such effects are conditional on trophic structure, and the variation within and covariation among response and effect traits. Taken together, these three factors can predict when ecosystems are poised to lose or gain function with ongoing biodiversity change.

Land use alters trophic redundancy and resource flow through stream food webs

“…In contrast, the urban sites with high nutrient loading and lower discharges were characterized by having lower trophic redundancy and a more homogenized energy flow as indicated by higher MNND and SDNND values, respectively. Local extinctions in ecosystems with low trophic redundancy can lead to a collapse of a functional group (Mason, Mouillot, Graham, & Bellwood, ) and negatively affect the functioning of the entire ecosystem (Heilpern, Weeks, & Naeem, ; Vinebrooke et al., ; Wallace & Webster, ).…”

Trait structure and redundancy determine sensitivity to disturbance in marine fish communities

“…Global environmental changes are threatening the sustainability of ecosystem functions and services, with severe consequences for human livelihood and well‐being (Bellard, Bertelsmeier, Leadley, Thuiller, & Courchamp, ; Cheung, Reygondeau, & Frölicher, ; Mora et al, ; Smith & Myers, ). It is therefore crucial to understand how variation in biodiversity may influence the sensitivity of communities and ecosystems to environmental change (Beaugrand, Edwards, Raybaud, Goberville, & Kirby, ; Heilpern, Weeks, & Naeem, ; Nolan et al, ; Segan, Murray, & Watson, ). Species diversity has been shown to sustain ecosystem productivity and stability under environmental disturbances (Isbell et al, ; Liu et al, ; Mellin, Bradshaw, Fordham, & Caley, ; Schneider, Brose, Rall, & Guill, ).…”

Compensatory responses can alter the form of the biodiversity–function relation curve

“…Although the present study was unable to account for processes that act over longer time scales, such as adaptation [85,86] and evolutionary change [87,88], our findings suggest that an immediate challenge is to determine the circumstances under which species exhibit compensatory responses (e.g. [21]) and whether or not the presence of compensatory processes refine understanding of biodiversity–function relations. In the meantime, we advocate that management efforts should prioritize the conservation of species based on their contribution to maintaining multiple ecosystem processes and functions.…”

“…Many of these events are associated with regime shifts, in which substantive rearrangement in functional trait composition and the use of novel space following species decline takes place and has concomitant effects on ecosystem properties [20]. These effects are not necessarily negative, the realized level of functioning can be conditional on trophic structure and/or the variation within, and covariation between, the response and effect traits of the surviving community [21]. This means that the level of functioning may be maintained, reduced or enhanced relative to the pre-extinction condition.…”