Water-related ecosystems' mapping and assessment based on remote sensing techniques and geospatial analysis: The SWOS national service case of the Greek Ramsar sites and their catchments

Abstract

Mapping and assessment of water-related ecosystems is a challenging task that requires advanced processing techniques with clear rules and standards in terminology and definition of class features. These ecosystems are hydrologically and ecologically connected at catchment level and co-exist within a human context. The SWOS (Satellite based Wetland Observation Service - Horizon 2020) national service case for mapping and assessing the 10 Greek Ramsar wetland sites and their catchment areas is built on the requirements of the Ramsar Convention on Wetlands and of the Aichi Biodiversity Targets of the Strategic Plan for Biodiversity 2011–2020. It contributes directly to Sustainable Development Goal (SDG) Global Indicator 6.6.1 “Sub-Indicator 1 – spatial extent of water-related ecosystems”. An Object-Based Image Analysis (OBIA) approach was adopted using Sentinel-2 satellite images for the year 2017, to discriminate 31 classes (wetland and non-wetland) over an area of 2,015,591 ha. The classification model was further adjusted to Landsat 5 TM imagery of previous years (1986–1987) in order to extract possible changes in the spatial extent of water-related ecosystems. The Mapping and Assessment of Ecosystems and their Services (MAES) ecosystem typology, as this was enhanced within SWOS, was applied. Results demonstrate the effectiveness of the employed classification model, techniques and rules, in obtaining highly accurate (over 90%) mapping results on the spatial extent of water-related ecosystems. Also, they highlight the contribution of Earth Observation (EO) and geospatial analysis in assessments of area-based changes and their causes, as well as in identification of conservation and management priorities (i.e. areas for restoration). In addition, to address the need to strengthen national capacities, the established SWOS service lines have been used as a contribution to the user community.