Warmer climate threatens the occurrence of giant trees in the Amazon basin

Giant trees in the Amazon serve as critical carbon sinks and underpin diverse forest ecosystems. Yet, these emergent giants are increasingly vulnerable to climatic change, jeopardizing their distribution and ecological niches. Here, we integrate ecological niche modeling with LiDAR, forest inventory, global repository data, and bioclimatic variables to reconstruct and forecast the distribution of Amazonian giant trees under past, present, and future climate scenarios (SSP1-2.6 and SSP5-8.5) across multiple biogeographic provinces. Employing MARS, Random Forest, MaxEnt, and GAM algorithms, we assess the influence of key climatic drivers, such as isothermality, maximum temperatures, and precipitation patterns, on habitat suitability for two emblematic species: Dinizia excelsa and Goupia glabra. Our analyses reveal that while both species exhibit distinct climatic responses, Tall trees obtained by LiDAR and Dinizia excelsa are particularly sensitive to heightened temperature extremes, notably in the Guiana Shield and Roraima Provinces. In contrast, Goupia glabra displays a broader tolerance to precipitation variability. Under the high-emission scenario (SSP5-8.5), projections indicate a loss of up to 45 % of suitable habitat by 2080, especially in southern provinces such as Xingu-Tapajós, where drought frequency and temperature extremes are expected to intensify. Conversely, the low-emission scenario (SSP1-2.6) may foster habitat stability or modest expansion in the northern Amazon. These findings underscore the urgent need for targeted conservation strategies to safeguard critical refugia and enhance ecosystem resilience in the face of global climate change.