In January 2019, a seizure of 3.3 tonnes of ivory in Uganda revealed something startling: marks on some of the tusks suggested they may have come from a stockpile of ivory kept, it was thought, strictly under lock and key by the government. of Burundi.
A new study by eminent Professor Thure Cerling and colleagues at the University of Utah, published in Proceedings of the National Academy of Sciences, uses carbon isotope science to show that tagged tusks had more than 30 years old and had somehow found their way from the guarded government. stock in the hands of illegal ivory traffickers. The results suggest that governments that maintain stockpiles of ivory may want to take a closer look at their inventory.
Isotope signatures of ivory
Cerling is a pioneer in the use of isotopes to answer questions regarding physical and biological processes. The “isotopes” of a given element refer to the atoms of the element whose number of neutrons varies and whose mass therefore varies very slightly. A carbon-14 isotope has one more neutron than carbon-13, for example.
Some isotopes are stable and some are unstable. Unstable isotopes decay into other isotopes or elements through radioactive decay. Since the decay rate is known for unstable isotopes, we can use the amounts present in a sample to determine ages. This is how carbon dating works: it uses the decay rate of unstable carbon-14 to determine the age of organic matter.
About a decade ago, Cerling attended a presentation at the University of Washington’s Sam Wasser College, which was studying wildlife genetics and using these tools to investigate when and where poaching took place. from wildlife. Cerling, recognizing that his expertise in isotopic science might be able to add useful information, began an ongoing collaboration with Wasser.
In 2016, Cerling, Wasser and their colleagues published a study that addressed a key question in the ivory trade: how old is the ivory seized by governments? Some traders claimed that their ivory was old, taken before 1976, and therefore exempt from sales bans. And with the average size of ivory seizures over 2.5 tonnes, researchers, governments and conservationists are wondering how much ivory is recent and how much is from criminal stockpiles – or stolen. in one of the many ivory stockpiles held by the governments of some African countries.
“Governments keep stocks for multiple reasons,” says Wasser. “They hope to sell the ivory to generate income, sometimes to support conservation efforts. However, they can only sell ivory from elephants that died of natural causes or were shot as problem animals. They can’t sell seized ivory because they don’t. I don’t know he’s from the country. »
Combining isotope data from Cerling and genetic data from Wasser, the 2016 study found that more than 90% of seized ivory came from elephants that had been killed less than three years previously. This result is sobering, showing active and well-developed poaching and export networks. The study seemed to show that little ivory from government stocks had ended up on the black market.
Marked Tusks
But Uganda’s 2019 ivory seizure showed something worrying. Some of the tusks bore marks that looked suspiciously like the marks that CITES, the Convention on International Trade in Endangered Species of Wild Fauna and Flora, uses to inventory stockpiled ivory.
Due to marks observed on some ivory samples,” Cerling said, “it was thought that a number of samples from this shipment might be linked to material held in government stockpile in Burundi. We were asked to date samples from this seizure, as well as three other recent ivory seizures, to see if any samples might possibly have come from older stocks. »
To determine the age of the ivory, the researchers took small samples of the tusks and analyzed them to determine the amount of carbon-14 isotopes in each sample. They were specifically looking for the amount of “bomb carbon” in the tusks. Between 1945 and 1963, nuclear weapons testing doubled the amount of carbon-14 in the atmosphere, so every living thing that has consumed carbon since then – including you – has a measurable carbon-14 signature. The amount of carbon-14 in a sample of ivory that has not yet undergone radioactive decay can tell scientists when the ivory has stopped growing or when the elephant has died.
The method requires some calibration, using samples from organisms living in the same area. Some of the samples came from schoolchildren in Kenya, through a program called “Kids and Goats for Elephants”. Because most families in rural Kenya raise goats, the program, led by Cerling and Paula Kahumbu of WildlifeDirect, engages children to collect samples of goat hair for isotopic analysis. Isotope data is useful for many applications, including combating elephant poaching and, in this case, calibrating the rate of bomb carbon decay for more accurate dating of ivory.
A significant result
Researchers analyzed ivory from four seizures in Angola, Hong Kong, Singapore and Uganda. The genetic data ensured that they were not taking two tusks from the same individual. Results from analysis of seizures in Angola, Hong Kong and Singapore were as expected – samples were mostly regarding three years following the elephant’s death, with no tusks taken more than 10 years previously .
But the seizure in Uganda, with the inventory marks on the tusks, showed something quite different. Nine of the 11 tusks tested had been collected more than 30 years previously, with death dates between 1985 and 1988. These dates correspond to the age of the ivory in the Government of Burundi stockpile, which was inventoried and stored in sealed containers in 1989.
“My suspicions have been confirmed,” Wasser said. “The biggest surprise was how much elephants were killed around 1989.” At the time Burundi built up its stockpile, a condition for joining CITES, which helps governments manage elephant reserves ivory, was that the ivory to be stored was old. The results suggest that was not the case, Wasser says, which would have violated Burundi’s terms of membership in CITES.
“The hope is that CITES will ask for the stock to be reinventoried,” says Wasser, “including the aging of randomly selected tusks and the securing of remaining stocks.”
