A DNA Method to Verify the Integrity of Timber Supply Chains; Confirming the Legal Sourcing of Merbau Timber From Logging Concession to Sawmill

Several methods are employed by the timber industry to try to restrict the flow of products from illegal or unsustainable sources into timber supply chains. The most commonly applied are systems of log marking and associated documentation that accompany the logs. However this system is open to falsification, particularly between the logging concession and the timber mill, where the majority of illegally logged timber enters the supply chain. This paper describes the development of a methodology to track a unique genetic fingerprint for single logs of merbau, Intsia palembanica (Leguminosae), a high-value Indonesian timber species, from logging concession to the mill, where the DNA profile of individual logs is difficult or impossible to falsify. We find that whilst the ability to extract DNA and amplify a PCR product from logs decreases slightly between forest concession (59.2%) and mill (41.9%) samples, that overall enough samples worked across the 14 microsatellite markers to provide an exact genotype match between forest and sawmill samples for 27 out of 32 logs. Furthermore for these 27 samples, the probability that an illegal log with an exact genotype match to forest samples had been substituted was very low (less than 10-5) for 18 samples, was low (between 10 and 10 ) for 7 samples and was moderate (10 ) for 2 samples. Improvements to DNA extraction and amplification success are recommended to improve this protocol, and there was a negative correlation between locus size and amplification success but a positive correlation with allele number. However, overall we propose that this methodology is now suitable for broad-scale industry application to track legally harvested timber and check for illegal substitutions along supply chains.