Ecosystem service flows: A systematic literature review of marine systems

Understanding and quantifying ES flows is essential for the sustainable management of social-ecological systems, as it directly captures the human-nature interactions within the system and not solely its individual elements. Especially in degrading marine systems, most ES assessments focus solely on either biophysical or socio-economic elements of these social-ecological systems, failing to directly capture the human-nature interactions. This systematic literature review aims to capture the state of the art of ES flow studies to improve the knowledge base on marine ES flows while highlighting knowledge gaps and discussing future research pathways. Within the review we extract information on: i) the ES flow definitions, classification systems, and indicators; ii) the scales of assessment and methods used to assess marine ES flows; and iii) the types of assessment outputs. 82% of the reviewed ES flow assessment methods were spatially explicit. 63% of the studies assess marine ES flows locally. Across-scale ES flows are rarely taken into account. We detect a broad range of conceptualizations within marine ES flow literature. We thus propose an updated definition for ES flows in which they are defined as a spectrum within the social-ecological system, within which different ES flow indicators are placed depending on the relative contributions of biophysical or socio-economic attributes. Based on the extracted information and detected literature gaps, we propose a set of four criteria that should be the minimum required information when referring to ES flows: i) the relative contributions of biophysical and socio-economic attributes present in ES flow indicators; ii) identification of the supplying and receiving systems; iii) the direction and branches of flows; and iv) the spatial and temporal scales across which ES flows occur.