Rapid seaward expansion of seaport footprints worldwide

As global maritime traffic increases, seaports grow to accommodate and compete for higher volumes of trade throughput. However, growth trajectories of seaport footprints around the world have gone unmeasured, likely because of a lack of readily available spatio-temporal data. Here, we use geospatial analysis of global satellite imagery from 1990–2020 to show that 65 seaports among the world's top 100 container ports, as ranked by reported throughput, have been expanding rapidly seaward. Collectively, these seaports have added approximately 978 km2 in gross port area in three decades through coastal land reclamation. We also find that the relationship between footprint expansion and throughput volume is highly variable among seaports. Understanding patterns of seaport expansion in space and time informs global assessments of critical infrastructure and supply chain vulnerability to climate-driven hazard. Seaport expansion also sets up complex trade-offs in the context of environmental impacts and climate adaptation.