A report from scientists and Indigenous experts documenting biodiversity and Indigenous stewardship of the Upper Içá River region of Amazonian Brazil.   In May 2025, Brazilian and international scientists worked alongside Indigenous Tikuna, Kukama, and Kambeba experts to explore an expanse of forests, rivers, and seasonally flooded wetlands in Brazil's Upper Içá River region. Over three weeks, the multidisciplinary team documented the geology, biodiversity, history, and stewardship that make this 350,787-hectare landscape a priority for conservation and Indigenous land rights.   The team recorded an extraordinary richness of plants, vertebrates, and aquatic habitats; robust populations of large mammals and birds; and clear evidence of a long history of Indigenous stewardship. That history is visible both in cultural landmarks across the region and in the day-to-day practices through which local people shape and sustain the landscape.   This report brings together the expedition findings into the cohesive narrative of a vast, well-preserved mosaic—scientifically understudied but deeply known by Indigenous communities—and highlights its importance for regional planning and conservation in the western Amazon. The text is in English, with summaries in Tikuna, Kukama, and Kambeba.