Waterworld: increasing coastal urban waterways and the dilemmas for ecology and society

Coastal urban expansion has transformed shorelines worldwide, replacing wetlands and floodplains with engineered residential waterways. The rapid proliferation of artificial canals and islands, from Palm Islands in the United Arab Emirates to China's coastal megaprojects, has created a global form of “ocean sprawl”, yet its ecological consequences remain largely unquantified. Here, by analyzing Google Earth satellite imagery, we recorded 4389 km of urban waterways, a 10.3% expansion of such waterways since our 2007 assessment, and evaluated the extent to which these systems have been studied for ecological, hydrological, and environmental impacts. Despite over 50 years of construction, empirical evidence remains sparse, and sustainability interventions are rarely tested. Our findings highlight the urgent need for systematic evaluation frameworks that guide both the design of new waterways and in retrofitting existing developments. Such approaches are essential to ensure that expanding ocean sprawl delivers measurable benefits for biodiversity, the environment, and local communities.