Win-wins for biodiversity and ecosystem service conservation depend on the trophic levels of the species providing services

Confronted by significant impacts to ecosystems world-wide, decision makers face the challenge of maintaining both biodiversity and the provision of ecosystem services (ES). However, the objectives of managing biodiversity and supplying ES may not always be in concert, resulting in the need for trade-offs. Understanding these potential trade-offs is crucial for identifying circumstances under which conservation strategies designed to maximise either biodiversity or ES will result in win-win or win-lose outcomes. One important factor that may influence these outcomes are species interactions and the structure of the networks in which they are embedded. We combine optimisation and network theory to investigate the difference in species prioritisation and management outcomes when targeting biodiversity or ES, by considering trophic interactions between species. We analyse 360 simulated ecosystem networks with different ecosystem structures, including the trophic level of the species providing the ES, the number of ES considered, and the food web connectivity. We then illustrate the framework on a saltmarsh case study. We find that trade-offs between biodiversity and ES depend on the network structure of the ecosystem being managed. The trophic level of the species providing the ES is an important determinant of optimal species protection priorities and the biodiversity-ES trade-offs. A strategy targeting ES leads to similar levels of biodiversity conservation (a win-win situation) only when basal species provide the services. In contrast, food web connectivity and the number of services considered have little impact on biodiversity-ES trade-offs. Synthesis and applications. Our research provides the first optimisation model to examine trade-offs between a biodiversity- or ecosystem service-based approach for managing a network of interacting species that provide services. Importantly, results from considering species-services interactions in ecosystem network dynamics can provide managers with quantitative insights to identify opportunities for win-wins and or to avoid win-loss outcomes, by focusing on the trophic level of the species providing services. Future research could build on our model to add multiple interaction types among species, ecosystem functions, and ecosystem services to analyse optimal ecosystem management for multiple conservation objectives.