Can stable isotopes and radiocarbon dating provide a forensic solution for curbing illegal harvesting of threatened cycads?

Abstract

Cycads in South Africa are facing an extinction crisis due to the illegal extraction of plants from the wild. Proving wild origin of suspect ex situ cycads to the satisfaction of a court of law is difficult, limiting law enforcement efforts. We investigated the feasibility of using multiple stable isotopes to identify specimens removed from the wild. Relocated and wild specimens from two species in the African genus Encephalartos (E. lebomboensis and E. arenarius) were sampled. 14C analysis indicated that a ± 30-year chronology could be reliably obtained from the cycads. For E. arenarius, pre-relocation tissue was consistent with a wild origin, whereas tissue grown post-relocation was isotopically distinct from the wild for 87Sr/86Sr and δ15N. For E. lebomboensis, δ34S, δ18O, and 87Sr/86Sr were different between relocated and control plants, consistent with the >30 years since relocation. Our findings demonstrate the potential for a forensic isotope approach to identify illegal ex situ cycads.