Prototyping the Development of a New Map of World Coastal Ecosystems

A recent elaboration of a 30 m spatial resolution, 2014 Landsat image-derived global shoreline vector was used to separate coastal lands from coastal waters in a new partitioning of the global shorezone. The global shoreline vector was segmented into approximately 4.5 million one kilometer segments, the midpoints of which were then extracted into a global shoreline points dataset. Each point was then attributed with ecologically relevant information about its adjacent ocean environment, adjacent land environment, and the shoreline itself. The attributes describing the ocean environment were derived from earlier work to identify global ecological marine units (EMUs), and included an integrated measure of physical properties (temperature, salinity, and dissolved oxygen), an integrated measure of nutrients (nitrate, phosphate, and silicate), turbidity, tidal range, wave height, and chlorophyll. The attribute describing the land environment was the adjacent World Climate Region, an integrated measure of baseline temperature and precipitation. The attributes describing the coastline itself were its sinuosity and the slope profile of a 200 meter perpendicular line segment extending 100 meters landward and 100 meters seaward from every point. Preliminary statistical clustering was conducted on all points, with all nine attributes included, to group points with similar land-side, water-side, and coastline properties. The clustering routine accommodated the mix of categorical and continuous variables in the nine inputs. An assessment of optimal cluster numbers identified 23 clusters as a balanced set of groupings. Fewer than 23 clusters appeared overly simplified and largely responsive to latitudinal gradients, whereas more than 23 clusters did not identify new regional groupings, instead demonstrating successive partitioning of the parent clusters. The 23 clusters represent the identification of a preliminary set of standardized (replicable), robust World Coastal Ecosystems with potential utility for conservation assessments and priority setting, blue carbon assessments and coastal ecosystem accounting, research, and resource management. The work was commissioned by the Group on Earth Observations, a consortium of over 100 nations seeking to leverage earth observation for societal benefit.