Combined genetic and chemical methods boost the precision of tracing illegal timber in Central Africa

Enforcement of national and international laws banning illegal tropical timber trade hinges on independent origin verification, such as with genetic or chemical wood properties. This is of particular concern in Central Africa, where illegal trade prevails. However, tracing methods have not yet consistently achieved high accuracy (>90%) at small spatial scales (<100 km). Where high precision is required but individual methods fall short, combining methods may improve results, because drivers of wood properties differ. Here, we assessed the individual and combined identification potential of three methods (genetics with 238 plastid Single Nucleotide Polymorphisms, 3 stable isotopes, and 41 elemental concentrations). The combined approach achieved unprecedented accuracy in Central Africa, identifying 94% of samples within 100 km of their origin, outperforming individual methods (50-80%), and verifying real origin for 88%. These findings show that method complementarity boosts tracing accuracy and spatial precision, crucial for high-value timbers or high-risk regions.