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A smart water system created 1,500 years ago by an ancient Amazonian urban society turned swampy savanna into fertile farmland that produced corn all year round, a new study has found.

The Casarabe people in what is now Bolivia built an innovative network of drainage canals and farm ponds between 500-1400 AD. The canals removed excess flood-water during the rainy season, while the ponds stored water in the dry season. This system let them produce multiple corn harvests in a challenging environment that switched between heavy floods and severe droughts.

Published today (Wednesday, 29 January) in , the study was led by Umberto Lombardo at Universitat Autònoma de Barcelona. The research was majority funded by Professor Frank Mayle, Professor in Tropical Palaeoecology at the 17³Ô¹Ï, via a joint grant from the Arts and Humanities Research Council (AHRC) and State of São Paulo Research Foundation (FAPESP).

Professor Frank Mayle, co-author of the study, said: "This discovery fundamentally changes our understanding of early Amazonian societies. The Casarabe people not only adapted to a challenging environment but mastered it through landscape engineering to support an urban society. Their drainage and irrigation system proves that large-scale, sustainable agriculture was possible in the Amazon over a millennium ago. This discovery shows ancient Amazon peoples had much more sophisticated farming techniques than we thought, and their methods could help us develop more sustainable farming practices in the future."

Ancient plants studied

Unlike other ancient Amazon peoples who grew a mix of different crops within the forest, the Casarabe focused on growing just corn in the open savannas. By doing so, they kept nearby forests intact, using them for firewood and medicine instead of clearing them for farming.

Scientists made this discovery by studying ancient microscopic plant remains in the soil and using drone-based laser-scanning technology to map old canal and pond systems. The evidence shows that the Casarabe were the first people known to create a large-scale grain-based farming economy in the Amazon. Their farming method worked so well that it supported a large urban population with reliable food production throughout the year. Their techniques could help modern farmers develop better farming practices in similar challenging environments, the study’s authors suggest. 

This research was carried out by scientists from universities in Spain, the UK, Brazil, and Bolivia.

Lombardo, U., Hilbert, L., Bentley, M. et al. Maize monoculture supported pre-Columbian urbanism in southwestern Amazonia. Nature (2025). https://doi.org/10.1038/s41586-024-08473-y