Ecological Network Resilience - Updating Projections of Ecological Networks under Optimistic and Pessimistic Scenarios of Biodiversity Loss

Abstract

Forecasting ecosystems under climate change requires multi-species approaches that account for ecological interactions through ecological networks. While previous projections have used network approaches mainly focusing on extinction-cascade directionality as a driver of ecological change, few multi-species projections have considered the resilience mechanisms of ecological networks to species extinctions. These mechanisms are link-loss sensitivity (the inverse of a network’s ability to withstand loss of links when interaction partners go extinct) and realisation of rewiring potential (the capacity to reallocate lost interactions to novel or existing partners). Using a new quantitative framework, we simulate compositional and network changes across globally distributed, in-situ sampled mutualistic frugivory networks. These simulations are based on species-specific climate-driven extinction cascades that incorporate both resilience mechanisms simultaneously. To assess the impact of network resilience mechanisms on biodiversity loss and network connectedness, we introduce and explore two-dimensional resilience landscapes defined by link-loss sensitivity and rewiring potential. We evaluate outcomes under optimistic and pessimistic resilience assumptions, and both low- and high-emission climate change scenarios to improve understanding of the potential consequences of extinction cascades across the Earth. Additionally, we compare climate driven projections with baseline scenarios that remove the least- and most-connected species in each network. In contrast to traditional models emphasizing bottom-up or top-down cascades, we account for bi-directional extinction processes to better reflect ecological reality. Our findings suggest that ignoring ecological network resilience mechanisms may significantly underestimate ecological change, particularly in terms of biodiversity loss and shifts in network connectedness under climate change.