Global Inputs and Impacts from Human Sewage in Coastal Ecosystems

Coastal marine ecosystems face a host of pressures from both offshore and land-based human activity. Research on terrestrial threats to coastal ecosystems has primarily focused on agricultural runoff, specifically showcasing how fertilizers and livestock waste create coastal eutrophication, harmful algae blooms, or hypoxic or anoxic zones. These impacts not only harm coastal species and ecosystems but also impact human health and economic activities. Yet few studies have assessed impacts of human wastewater on coastal ecosystems and community health. As such, we have lacked a comprehensive, fine-resolution, global assessment of the inputs and impacts of human sewage inputs that captures both pathogens and nutrient flows to coastal waters and the potential impacts on coastal ecosystems. To address this gap, we use a new high-resolution geospatial model to measure and map nitrogen (N) and pathogen - fecal indicator organisms (FIO) - inputs from human sewage for ~135,000 watersheds globally. Our modeled data is for 2015. The resulting dataset provides N and FIO wastewater inputs for each watershed globally (n = 134846). Data is provided at the watershed level, as well as the coastal 'pourpoint' (the location where the watershed empties into the ocean) and national-level estimates, as vector shape files (.shp). The N dataset separates the contribution from sewered, septic, and untreated (open deification) wastewater inputs to coastal waters. Furthermore, we provide global rasters (GeoTIFF .tif) of N coastal impacts created by propagating pourpoint N inputs for each treatment type into coastal waters using a plume model based on a logarithmic decay function. The N effluent plumes can be used to determine the extent to which different marine habitats are exposed to wastewater N. For full information, see: Tuholske, C.*, Halpern, B. S.*, Blasco, G., Villasenor, J. C., Frazier, M., & Caylor, K. (2021). Mapping global inputs and impacts from of human sewage in coastal ecosystems. PloS one, 16(11), e0258898. *Equal authorship Note: The coordinate reference system of the .shp files is ESRI:54009 - World Mollweide and the .tif files is EPSG:4326 - WGS 84 - Geographic.