Assessing the robustness and resilience of subsistence ecosystem services using a socioecological network

Abstract

Understanding the vulnerability of ecosystem services to environmental change and species loss is critical to supporting communities dependent on services for well-being and livelihoods. However, assessments of ecosystem service resilience often overlook the complexity of socioecological systems, including the cascading effects of species loss and adaptive responses of biodiversity and humans. We constructed a socioecological network representing ecosystem service provisioning in a tropical farming community, linking frugivore - plant interactions with provision of local services such as food and firewood, and simulated species loss under environmental change scenarios. We quantified the robustness of ecosystem services and identified key species and interaction pathways for such, and incorporated interaction rewiring into our simulations to assess the resilience of network and ecosystem services as species and humans adapt to environmental change. Ecosystem service provisioning in our network was generally robust to simulated species loss. On average, our network could withstand the loss of over 80% of species before collapsing, with the loss of all services occurring in only the most extreme environmental change scenarios. When service loss did occur, such as the loss of firewood, it was driven by secondary extinctions after loss of primary species propagated through the network. Interaction rewiring enhances ecosystem service resilience, allowing the loss of 18% more species before network collapse. Rewiring also altered the relative importance of individual species and their interaction pathways in maintaining resilient services. Species such as sago and coconut do not directly provide firewood and initially did not play an important role in maintaining robust firewood services with limited network connectivity. However, with rewiring these species helped maintain resilient firewood services in 20% more simulations, reflecting the importance of indirect interaction pathways and adaptivity. These findings demonstrate that 1) species can maintain resilient ecosystem services even when they do not directly provide the service and 2) the adaptive capacity of humans and biodiversity can substantially enhance ecosystem service resilience. Overall, our study provides a framework for more accurately assessing the consequences of species loss on ecosystem services and human livelihoods by explicitly accounting for socioecological complexity and adaptability.