The influence of Amazonian rivers and landscape changes on species origin and distribution remains debated. Here, we combine sedimentary, geomorphological, and chronological evidence from Central Amazonia to show that the main Amazonian rivers constructed large tracts of land that now support present-day Amazonian upland forest (terra firme). These deposits record a sequence of landscape rearrangements driven by river processes in Central Amazonia during the Pleistocene redefined the spatial boundaries of key habitats critical for many species. Our findings reveal that Amazonian rivers have acted not only as biogeographic barriers but also as powerful agents of landscape and habitat transformation, offering a unified framework for understanding how geological and biological processes together shaped the evolution of Amazonian biodiversity.
Galeazzi et al. (2026) studied this question.