Detecting illegal timber


Detecting illegal timber

Determining the origin of timber is difficult as a result of which illegally felled wood still comes onto the market. Researchers from Wageningen University & Research (WUR) are working on new methods to detect illegal timber.

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It is estimated that 30 to 90% of tropical hardwood is felled illegally. Tampered documents, however, make it difficult to determine where imported wood comes from. Researchers from WUR are trying to determine the origin of wood based on its genetic and chemical profile. How does that work?

In September 2019, PhD students Bárbara Rocha Venancio Meyer-Sand and Laura Boeschoten from WUR went to the south of Cameron to do fieldwork. There, they are collecting wood samples from trees that will be used for the analysis. The aim of this and other trips is to build up a database of different tree species and to improve the methods.

The researchers use various techniques to take the samples. For the chemical analysis, they need wood from the innermost part of the tree. With a hollow drill, they can penetrate deep into the trunk.

Due to the hardness of the wood, they sometimes also use a power drill and then collect the sawdust.

The DNA analysis, however, requires wood from the outermost part of the trunk. This part contains the xylem and the phloem that transport the water and sugars respectively. ‘This living tissue provides the best quality DNA’, says principal researcher Pieter Zuidema. Using a special hammer, Rocha Venancio Meyer-Sand and Boeschoten obtain round discs from the bark for use in the analysis.

The researchers do not simply sample the first tree they find. They walk a lot through the forest and choose trees that are fifty metres to several kilometres apart from each other to obtain a spread. That allows them to study the relationship between genetic and spatial distance. So far, they have managed to use DNA analysis to distinguish African trees that are just fourteen kilometres apart from each other. ‘We hope that this will also prove successful for other trees’, says Zuidema.

Besides Cameroon, they are also doing research in the Republic of the Congo, Gabon, Indonesia and Malaysia. These countries export a lot of tropical hardwood, also to the Netherlands.

Back in the laboratories in Wageningen, the researchers dissolve the samples to analyse the chemical composition of the wood and to characterise the DNA. ‘We measure about sixty different chemical elements from the wood; elements that are vital for trees such as iron, sodium and magnesium but also elements that have no function such as cadmium or heavy metals’, says Zuidema. The concentration and composition are related to the soil type and therefore to the geographical origin of the tree. Ultimately, both analyses will help to determine whether imported wood is illegal.

In the long term, the researchers want to compile an extensive database that will help to detect illegal wood. Before such a database can be used to provide evidence in a legal case, more wood samples are needed, and the laboratory tests and analyses will have to satisfy strict guidelines. Zuidema: ‘We are therefore collaborating in a worldwide network for timber detection in which researchers, laboratories and authorities are joining forces.’

Text: Dirk-Jan Zom Photos: Jean Pierre Kepseu, Sander van den Bosch

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