By combining chemical and genetic analysis of wood, methods for detecting illegally harvested timber are being improved, making it possible to halt the trade in such timber, which INTERPOL and the FBI rank third among the world's most lucrative organised criminal activities.
The study shows that combining the results of chemical analysis with genetic markers from tropical broadleaved trees makes it possible to determine the origin of wood precisely, creating an effective instrument that could deter or even eliminate timber smuggling. According to INTERPOL data, the trade in illegally harvested timber is the third most lucrative criminal activity after counterfeit goods and drug smuggling.
The researchers analysed genetic data, stable isotopes and the concentrations of a number of trace elements in around 250 trees at 13 sites in Cameroon, Gabon and the Republic of the Congo, and found that, by combining these three types of evidence, the place of origin could be identified for 94% of the samples to within a radius of 100 kilometres.
“European Union legislation requires the precise origin of timber to be stated when it is brought onto the European market. Given how frequent cases of fraud are, supervisory authorities need to be able to verify that origin. For example, by analysing the properties of the timber. The study shows that, when a range of wood properties is assessed, such checks can be very accurate,” says Laura Boeschoten, one of the study's authors.
The study could prove highly significant, because timber traders face not only the European Union (EU) Deforestation Regulation (EUDR) but also other rules requiring importers to prove that their timber imports are legal and do not come from illegally deforested areas. As a result, there will be strong demand for timber testing by independent laboratories.
The specifics of the scientific methods
The research team focused on Lophira alata, known as Azobé – a broadleaved tree with dense, extremely durable wood. Azobé wood is widely used in modern structural materials and engineered constructions. The timber is exported from areas in the Congo Basin. At 13 logging sites, the scientists took wood cores and cambium samples, from which a reference database was built. The researchers determined plastid nucleotide polymorphisms in order to capture the genetic structure. They measured three stable isotopes that encode climatic signals and quantified 41 trace elements reflecting the chemical composition of local soils.
Using each method on its own, the samples yielded the place of origin to within a radius of 100 kilometres in roughly 50-80% of cases. When the methods were combined, accuracy rose to 90%. That is a considerable achievement. “Some wood properties are determined by conditions that differ only over long distances. Other properties vary more between trees growing close to one another. In combination, the shortcomings of one method are compensated for by the other two,” explains co-author of the study Barbara Rocha Venancio Meyer-Sand.
Put simply, the genetic data narrow the geographical boundaries, elemental chemistry distinguishes local soils, and isotopes add climatic context. Together they point to the origin of the wood more precisely than any single method. The study assessed both identification, which involves assigning an unknown sample to one of the 13 reference sites, and verification, which checks whether the wood really does come from the stated location.
The results showed that combining the three methods achieved the best verification performance, confirming true claims in almost 88% of the simulated tests. This markedly improves the ability to reject false claims compared with the individual methods. Precise, laboratory-determined origin becomes a practical means of exposing forged documents and tracing illegal trade routes.
“Methods for determining the origin of wood are still at an early stage of development,” notes Pieter Zuidema, professor at Wageningen University & Research in the Netherlands and the project's research leader. “In recent decades, researchers have mainly concentrated on developing and promoting their own individual methods. We are taking a different approach by comparing and combining the methods. Combining them is, of course, expensive, and in practice it will only be used for very valuable tree species or where the risk of illegality is very high.”
The routes taken by illegally harvested timber
Illegally harvested timber is flooding global supply chains. INTERPOL warns that 15-30% of all timber sold worldwide may have been harvested illegally. Gabon's border guard service, for instance, recently detained a Chinese vessel loaded with unprocessed saw logs, despite the fact that the export of unprocessed timber from Gabon is categorically prohibited. Russian roundwood, meanwhile, has been prepared for loading at Manzhouli, China's largest inland port, showing how “risky timber” can (and does) enter global supply chains in transit through China. A special Source Certain report warns that this route can be used to circumvent the control tools of the FSC and PEFC certification systems, increasing the risk that timber of Russian origin, for example, ends up in Australian supply chains through incorrect or misleading declarations.
The study's authors also acknowledge the trade-offs. Multi-method testing brings higher costs and logistical demands, and geographical gaps remain in the current reference database. Central Gabon and part of the Democratic Republic of the Congo were not included in the sampling. To strengthen operational readiness, the team recommends widening the geographical coverage, adding nuclear DNA markers, expanding the isotope groups and increasing elemental resolution.
The study was carried out in collaboration with researchers in the Congo Basin region
“We provided them with training, carried out joint fieldwork and shared the responsibilities. We achieved the results together,” said B. Rocha Meyer-Sand, underlining the study's capacity-building approach and the importance of local partnerships. If regulators, importers and enforcement bodies were to invest in expanded reference collections and compatible testing systems, laboratory-determined origin could be used as a routine and effective response to a timber trade that has long had a problem with falsified origins and illegal profits.
Further information: Boeschoten, L.E., Rocha Venancio Meyer-Sand, B., Boom, A. et al. Combined genetic and chemical methods increase the accuracy of illegal timber tracing in Central Africa. Commun Earth Environ 6, 789 (2025). https://doi.org/10.1038/s43247-025-02698-z
Plastids are organelles of plant cells. They can take various forms. A distinction is made between green ones (chloroplasts), yellow, orange and red ones (chromoplasts) and colourless ones (leucoplasts). Under certain conditions, plastids can convert from one type into another. In autumn, for example, chloroplasts turn into chromoplasts and leaves take on a yellowish or reddish hue.
The Australian laboratory company Source Certain provides services to state institutions and to private commercial and scientific bodies, verifying the origin of products by testing physical samples to ensure they match the origin information stated in digital or physical documents. Source Certain works in the fields of trace element analysis (TEA) and stable isotope ratio analysis (SIRA). The laboratory draws on its expertise in both trace element analysis and isotope testing to deliver better origin information than other service providers.