The chemical composition of tropical timber, for example, used for bridges or in window frames, reveals where the trees were growing. This can help to trace timber origin and to reduce illegal trade. This is the main finding of large-scale collaborative research by Wageningen University & Research and international partners. The study collected wood samples from nearly 1000 timber trees from Central Africa and Borneo, and their chemical composition was analysed. The team found that chemical fingerprints of wood revealed their origin at sub-national scales.
Illegal tropical timber trade
Illegal timber trade ranks among the most profitable wildlife crimes and false declaration of origin is one of the main types of timber fraud. Trading routes are often complex, with timber passing through multiple countries before arriving at its destination. This increases the risk of declarations Timber fraud is especially high in the tropics, with some countries in the Congo Basin estimated to have up to 90% illegally exported timber.
Recent legislation in the European Union demands timber traders to prove that their products are legally obtained and do not come from deforested areas. Laura Boeschoten, a PhD candidate at Wageningen University & Research and lead author of the study published this week in Environmental Research Letters: “This means that timber origin must be reported when products are brought to the European market. For example, when arriving at Rotterdam Harbour. Independent methods to verify timber origin will become crucial for the enforcement of this new law. Multi-element analysis, as applied in our research, could be an effective tool in achieving this.”
Defining a chemical fingerprint
The team analysed the chemical composition of wood samples: their ‘fingerprints’. Boeschoten: “A large number of chemical elements were measured at once (such as magnesium and calcium) by using a mass spectrometer. As a next step, we used machine learning methods to relate the wood chemical composition to its geographic origin.” Multi-element analysis has already been put into practice to verify the geographic origin of commodities such as asparagus, bananas, and tea, but this study is the first to apply it to timber.
Successful tracing at a sub-national level
The researchers found substantial variations in the wood elemental composition of three major timbers. “We were thrilled to see significant differences at small spatial scales, such as between locations only 50 km apart,” says co-author Pieter Zuidema, a professor at Wageningen University & Research. “This is essential for tracing timber to a specific origin.”
The international team studied Red Meranti – an Asian timber used for window framing – and the African timbers Azobe and Tali – used in waterworks. As a result of the strong regional variation in chemical fingerprints, samples could be traced back to their sub-national origin with 86%-98% accuracy in Central Africa and to the forest of origin with 88% accuracy in Borneo. Independently collected blind samples from Central Africa were correctly assigned for 70-72% at a sub-national level.
The research was conducted as part of the Timtrace project, which aims to develop and test timber tracing methods using both chemical and genetic techniques. The Timtrace project is a collaborative effort with Universities and research institutes in Cameroon, the Republic of the Congo, Gabon and Indonesia and is funded by NWO.