Wetlands are valuable providers of ecosystem functions and services (EFS). Accounting for synergies and trade-offs among EFS represents a powerful tool to develop conservation strategies. However, quantifying EFS is complex, time- and resource-consuming, and requires extensive datasets. Consequently, studies generally rely on descriptors that aggregate ecosystems and indicators into coarser EFS categories. This simplification can misrepresent some EFS, such as biodiversity, which a single indicator cannot resume. While EFS quantification and wetland classification rely on similar methods, differences between wetland types are mostly ignored, being grouped into one category in most EFS studies. Ecosystem multifunctionality is also often overlooked. The objective of this project is to assess synergies and trade-offs among EFS of lake-edge wetlands using a large number of indicators measured at high spatial resolution. Our main questions are: 1) How contrasted are the EFS provided by three types of lake-edge wetlands? and 2) How are the synergies and trade-offs among EFS affected by the level of ecosystem and indicator aggregation?
To answer these questions, we sampled 37 lake-edge wetlands of three contrasted types: peatlands, alder swamps, and ash swamps. Using both field-collected and geomatic data, we quantified 25 indicators across 8 EFS: Biodiversity, support to pollinators, erosion control, water regulation, carbon storage, fishing, recreation and aestheticism. We put a particular emphasis on biodiversity, exploring eleven different metrics. We evaluated synergies and trade-offs using multivariate ordination and cosine similarities among the indicators. The wetland types were well discriminated by the EFS indicators, whereas peatlands and ash swamps were mirror opposites. While the choice of specific indicators did not influence the assessment of some EFS, others, such as biodiversity, showed important trade-offs. Each wetland type supported a different bundle of biodiversity indicators. Our results suggest that the level of ecosystem or indicator aggregation has a strong influence on EFS provisioning. These trade-offs should be considered in wetland conservation and restoration strategies.