Fire frequency restructures culturally important tree communities across forest and savanna landscapes in the Xingu Indigenous Territory

Fire has become an increasingly pervasive disturbance in southern Amazonia, and climate projections indicate that fire frequency is likely to intensify in the coming decades. These changes pose a growing threat to forest biodiversity and to the ecosystem services that sustain Indigenous peoples. Here, we evaluate how fire frequency influences the provision of ecosystem services derived from tree species used by the Kuikuro people in the Xingu Indigenous Territory (XIT), Brazil. We conducted forest inventories across a fire-history gradient ranging from zero to six burn events over the past 40 years, sampling 32 plots (10 × 10 m) distributed across forest (n = 20) and savanna (n = 12) vegetation types. For all trees with diameter ≥ 10 cm, we measured diameter, and recorded ethnobotanical uses reported by the Kuikuro people, grouped into three categories, (1) food, (2) construction/handcrafts, and (3) medicinal use. We also incorporated environmental predictors derived from remote sensing and soil data, including altitude, slope, soil pH, clay content, and bulk density. Across all plots, we recorded 92 tree species (54 in forest and 38 in savanna). In forest environments, 6.3% of species were used for food, 9.1% for medicinal purposes, and 17.3% for construction or handcrafts. In savanna, these proportions were 5.4%, 11.8%, and 3.6%, respectively. Regression analyses revealed that increasing fire frequency had a strong negative effect on the abundance of tree species used for construction/handcrafts and medicinal purposes in forest areas. In contrast, in savanna environments, fire frequency showed weaker negative effects on food- and construction-related species and a positive association with medicinal species. Because forests dominate much of the XIT and are becoming increasingly exposed to fire, our findings indicate that tree species providing materials for construction, handcrafts, and medicine are particularly vulnerable to altered fire regimes. These changes threaten not only forest biodiversity, but also the livelihoods, traditional knowledge, and cultural integrity of the Kuikuro people, underscoring the need for fire-sensitive management strategies that integrate ecological and Indigenous perspectives.