Bioavailable strontium isoscape for the Amazon region using tree wood

Illegal logging is a major environmental crime in the Amazon, driven by organized networks and causing severe ecological and economic impacts. Existing documentation systems, like Brazil’s “Forest Origin Document” (DOF), remain vulnerable to fraud, highlighting need for more reliable timber tracking methods. The isotopic composition of strontium (⁸⁷Sr/⁸⁶Sr) in wood has emerged as a promising tool for determining timber provenance. This study developed bioavailable Sr isoscapes for the Amazon using regression kriging and random forest to map ⁸⁷Sr/⁸⁶Sr ratios in tree wood. Wood samples from 67 trees across 21 sites were collected in collaboration with regional institutions. The observed ⁸⁷Sr/⁸⁶Sr range in plant exceeds previously reported global values, showing a strong contrast between the Amazon Trough and Precambrian Shields. Despite the limited dataset, both modeling approaches performed well, producing similar isoscapes and demonstrating that ⁸⁷Sr/⁸⁶Sr ratios in wood are highly predictable and geology – dependent. However, high intra - site variability in Precambrian cratons and limited differentiation across the Amazon highlight the need for additional sampling. The finding confirm the potential of Sr isoscapes to trace timber origin and combat illegal logging. While the models show strong predictive power in some regions, addressing current limitations through expanded sampling will improve accuracy. Future research can refine Sr isoscapes, enhancing their application in law enforcement and sustainable Amazon resource management.