Species Redundancy and Ecosystem Reliability

The concept of species redundancy in ecosystem processes is troublesome because it appears to con- tradict the traditional emphasis in ecology on species singularity. When species richness is high, however, eco- system processes seem clearly insensitive to considerable variation in biodiversity. Some elementary princi- ples from reliability engineering, where engineered redundancy is a valued part of systems design, suggest that we should rethink our stance on species redundancy. For example, a central tenet of reliability engineer- ing is that reliability always increases as redundant components are added to a system, a principle that di- rectly supports redundant species as guarantors of reliable ecosystem functioning. I argue that we should em- brace species redundancy and perceive redundancy as a critical feature of ecosystems which must be preserved if ecosystems are to function reliably and provide us with goods and services. My argument is de- rived from basic principles of reliability engineering which demonstrate that the probability of reliable sys- tem performance is closely tied to the level of engineered redundancy in its design. Empirical demonstrations of the value of species redundancy in ecosystem reliability would provide new insights into the ecology of communities and the value of species conservation.