Impact-Effect Pathways in Complex Dynamic Ecosystems : Using Knowledge of Ecosystem Functioning to Investigate the Impact of Management Interventions on Ecosystem Services

Ecosystems, and the ecosystem services they deliver, are subject to increasing pressures. Sustainable management requires a thorough understanding of the physical and ecological functioning of the ecosystem, the services delivered by the ecosystem to society and the management measures that can be taken. For extremely complex systems (marine, estuaries), there is a lack of instruments to get insight in the delivery of ES. We propose the use of a conceptual model to make the complexity of the system more transparent. This is crucial to be able to identify possible impact-effect pathways, which is a necessary step before we will be able to quantify management effects. We explicitely structured the relationships between management interventions, ecosystem functioning and ecosystem services to enable a description and quantification of impact-effect pathways. This is illustrated for some sediment management strategies in the Scheldt delta. The conceptual model is applied to make a qualitative assessment of the impact-effect pathways and next to use this as guidance towards a quantitiative assessment of effects. After completing this analysis, we discovered a new typology for ES based on how much knowledge of the system is required to be able to quantify each ecosystem service: (1) ecosystem services delivered by hydromorphological processes (e.g. flood risk regulation), (2) ecosystem services delivered by the basic components of the food cycle including water quality and primary production (e.g. climate regulation), and (3) ecosystem services delivered by the food web (e.g. food production for human consumption, recreation). The approach helps to identify the dominant impact-effect pathways through knowledge on ecosystem functioning that can be used to investigate the impact of management interventions on ecosystem services and prioritise in the quantification of these effects