Much of humanity lives close to the shore. A 2024 study estimated that in 2018, around 2 billion people lived within 50 kilometres of a coast, with half of them — about 15% of the world’s population — settled within just 10 km (A. G. Cosby et al. Sci. Rep. 14, 22489; 2024). Coastal zones are also growing faster than inland areas: between 2000 and 2018, some 460 million people moved to the coast, a shift the authors liken to adding 46 new megacities of 10 million residents each.
Nature Index 2025 Science cities
At the same time, sea levels are rising faster than at any point in modern history and coastal megacities are often more susceptible to subsidence. Indonesia’s US$51-billion plan to move its capital from Jakarta — one of the world’s fastest sinking cities — to a new city, Nusantara on the island of Borneo, by 2045, is one acute example.
