Topology of additive pairwise effects in food webs

Contrasting reductionistic versus holistic views, it is a general question whether adding the parts equals the sum. In the time of multiple drivers of anthropogenic change, it is a crucial issue, and better understanding additivity is critical for strategy and management. More particular research questions ask what are the community effects of the extinction of a single species and whether multiple local effects on different species will generate additive community responses. Here we perform food web simulations and study the community response to perturbing each species, one by one, and perturbing each possible pairwise combination of species. By comparing the two, we quantify additivity and analyze how does it depend on the topological positions of perturbed species pairs. Results increase the predictability of food web research, supporting systems-based conservation management and, possibly, multi-species maximum sustainable yield assessment in fisheries.