What evidence exists on how changes in marine ecosystem structure and functioning affect ecosystem services delivery? A systematic map protocol

Background The current biodiversity crisis calls for an urgent need to sustainably manage human uses of nature. The Ecosystem Services (ES) concept defined as « the benefits humans obtain from nature » support decisions aimed at promoting nature conservation. However, marine ecosystems, in particular, endure numerous direct pressures (e.g., habitat loss and degradation, overexploitation, pollution, climate change, and the introduction of non-indigenous species) all of which threaten ecosystem structure, functioning, and the very provision of ES. While marine ecosystems often receive less attention than terrestrial ecosystems in ES literature, it would also appear that there is a heterogeneity of knowledge within marine ecosystems and within the different ES provided. Hence, a systematic map on the existing literature will aim to highlight knowledge clusters and knowledge gaps on how changes in marine ecosystems influence the provision of marine ecosystem services. This will provide an evidence base for possible future reviews, and may help to inform eventual management and policy decision-making. Methods We will search for all evidence documenting how changes in structure and functioning of marine ecosystems affect the delivery of ES, across scientific and grey literature sources. Two bibliographic databases, Scopus and Web of Science Core Collection, will be used with a supplementary search undertaken in Google scholar. Multiple organisational websites related to intergovernmental agencies, supra-national or national structures, and NGOs will also be searched. Searches will be performed with English terms only without any geographic or temporal limitations. Literature screening, against predefined inclusion criteria, will be undertaken on title, abstract, and then full texts. All qualifying literature will be subjected to coding and meta-data extraction. No formal validity appraisal will be undertaken. Indeed, the map will highlight how marine ecosystem changes impact the ES provided. Knowledge gaps will be identified in terms of which ecosystem types, biodiversity components, or ES types are most or least studied and how these categories are correlated. Finally, a database will be provided, we will narratively describe this evidence base with summary figures and tables of pertinent study characteristics.