In this issue, Fuge`re et al. (2012) take a step towards understanding context dependency of biodiversity effects by examining how a resource-quality gradient modifies the influence of consumer diversity on leaf litter decomposition. The starting point of the study is the stress-gradient hypothesis of plant ecology (Grime 1979; Maestre et al. 2009; Malkinson & Tielbo¨ rger 2010), which was proposed based on observations that in stressful environments, plant performance improves in the presence of neighbouring plants (e.g. Callaway et al. 2002). The stress-gradient hypothesis suggests that competitive interactions structure plant communities in favourable conditions, but that facilitative interactions are instrumental in stressful environments where they enhance the realized niche of species that could barely persist in such conditions otherwise (Maestre et al. 2009; Malkinson & Tielbo¨ rger 2010). Facilitation, in turn, allows for complementarity effects of co-occurring species on ecosystem process rates. This is the rationale based on which Fuge`re et al. (2012) propose that stress imposed on animal communities also might enhance effects of biodiversity on ecosystem processes.