Chemical and isotopic compositions of tropical wood samples

Illegal logging is one of the leading causes of deforestation today. Sadly, tree species indigenous to regions critical to maintaining Earth?s ecological diversity also possess properties (i.e. appearance, aroma, etc.) desirable to humans, which often leads to exploitation. In 1992, due to illegal logging, Brazilian rosewood (Dalbergia nigra) became the first ever tree species to be listed in an appendix of the Convention of International Trade in Endangered Species of Wild Fauna and Flora (CITES), which prohibited international trade of the timber or other products from this species between entities which had voluntarily joined CITES. Despite its inclusion in Appendix I of CITES, the species continues to be logged illegally, traded internationally, and CITES often fails to prevent this and other protected species from entering the world market through illegal channels. In the U.S., CITES is implemented and enforced under Endangered Species Act regulations. Forensic analysis can help ensure legal, sustainable and traceable trade in timber and non-timber forest products by identifying products obtained illegally. Forensic analysis of timber based on comprehensively validated methods can provide robust results, including identification of the species and geographical provenance of timber samples. One approach to ascertain geographical provenance of wood samples is to utilize a combination of laboratory methods, which measure trace and crustal element concentrations and stable isotope compositions. This unique suite of chemical properties can then be correlated to authenticated/geocoded exemplars of both protected and non-protected wood species. Dalbergia nigra often arrives at ports of call mislabeled as non-prohibited South American Dalbergia spruceana in order to escape detection. To determine with certitude that trace and crustal element concentrations and stable isotopic compositions can be used to identify geographical provenance of Dalbergia and distinguish between Dalbergia species and look-alikes, the U. S. Fish and Wildlife Service and the U. S. Geological Survey collaborated to measure 239 wood samples from more than ten countries between the Tropic of Cancer and the Tropic of Capricorn (?the tropics?). The results of these measurements along with values for chemical and isotopic reference materials are presented.