Urbanisation of a growing tropical mega-city during the 21st century — Landscape transformation and vegetation dynamics

•Impervious surface cover increased in Bangkok by ∼ 474 km2 from ∼ 2004 to ∼ 2018.•Space-for-time substitution approaches can predict future vegetation dynamics.•∼583 km2 of grassland and ∼ 94 km2 of rice-fields were lost; tree-cover grew by ∼ 137 km2.•Expansion, not densification, drove these changes — raising heat stress & flood risk.•Densification drove substantial tree-cover loss, reducing ecosystem services, & biodiversity.•Schemes promoting urban growth through densification must increase tree protection.