The illegal trade in elephant ivory is being fueled almost entirely by recently killed African elephants, not by tusks leaked from old government stockpiles, as had long been suspected. That’s the conclusion of a new study, which relies on nuclear bomb tests carried out in the 1950s and ’60s to date elephant tusks and determine when the animal died. The findings could help efforts to halt the illegal trafficking of ivory, but they also reveal just how little is known about the criminal networks behind elephant poaching.
“It’s a really important study, and shows that elephant ivory is going practically straight from where an animal was poached to the market,” says Elizabeth Bennett, a wildlife biologist and vice president for species conservation at the Wildlife Conservation Society in New York City, who was not involved in the study. “It tells us that if we can stop the poaching, we can dry up the ivory pouring out of Africa.”
But stopping the poaching is a tall order. Despite an international ban that prohibits the sale of ivory from elephants killed after 1989 (the seller must have a permit from the United States or foreign government verifying the age), the ivory market is thriving, largely thanks to young, low- to middle-income people in the United States and Asian countries, like Vietnam and China, who see ivory jewelry and carvings as status symbols—and who mistakenly think that buying only a small piece does not hurt elephants. To meet the demand, poachers are killing some 50,000 elephants a year, an unsustainable rate. Black market prices for ivory in China and elsewhere run about $1000 per pound. A recent survey showed that poachers slaughtered nearly 30% of East Africa’s savanna elephants from 2007 to 2014, some 144,000 animals. Poachers also killed nearly two-thirds of central Africa’s forest elephants between 2002 and 2013. Fewer than 400,000 elephants are believed to remain in 18 sub-Saharan countries.
Law enforcement officials are stymied because they have not been able to crack the criminal syndicates believed to be behind the illegal trade, says Samuel Wasser, a conservation geneticist at the University of Washington in Seattle and one of the study’s authors. Still, between 2002 and 2014, police and customs officials intercepted 14 large shipments of ivory in nine nations, including Kenya, China, Malaysia, the Philippines, and Singapore. Using DNA collected from these tusks, Wasser previously showed where the ivory came from.
“In any forensics case, you need the when and the where,” says Kevin Uno, a geochemist at Columbia University’s Lamont-Doherty Earth Observatory, and another co-author. “Now, we have both.”
To get the “when,” the scientists collected ivory from the pulp cavity, or roots, of 231 tusks—the same tusks that Wasser and his colleagues had analyzed to show the “where.” An elephant’s most recently formed ivory tissues are found inside the roots of the tusk, which grows outward. Using a technique that Uno and his colleagues previously developed, the scientists measured the amounts of the radioactive isotope carbon-14 in these tissues. The isotope (an atom with the same number of protons, but different numbers of neutrons), which derives from open-air nuclear bomb tests in the 1950s and ’60s, remains in the atmosphere and is taken up by plants through photosynthesis. And because elephants consume plants that contain the isotope, it is also found in their bodies—including their tusks. The ivory forming in an elephant’s pulp cavity can thus provide an accurate record of the date of the animal’s death, the scientists say.
More than 90% of the samples came from elephants killed less than 3 years before the ivory was seized, the team reports today in the Proceedings of the National Academy of Sciences. Many of the tusks were probably confiscated within only several months of the animals being killed. Just four tusks had a lag time of more than 5 years between the elephant’s death and the seizure; and only a single specimen came from an elephant killed about 19 years earlier.
That “nullifies the idea that old ivory is being smuggled,” Uno says. “That’s a significant finding because it means that there’s no evidence for a lot of unfounded rumors, like corrupt government officials loading 747s with ivory and sending them to China,” adds George Wittemyer, a conservation biologist and elephant expert at Colorado State University in Fort Collins who was not involved in the study. Indeed, at least 21 countries have destroyed large ivory stockpiles in recent years; Kenya burned 105 tons earlier this year.
But the study also points to some worrisome trends: Since 2011 the lag time has increased by 2 to 3 years, and the tusks have been getting smaller. That could mean that “fewer large animals are left, so the poachers are having a harder time filling a container,” Wittemyer says. Similarly, it reveals that ivory taken from elephants in East Africa has been moved faster than that collected in West Africa, he says, “perhaps because the West African forest elephants grow more slowly, or they’re harder to find.”
Ultimately, the scientists hope their research will help law enforcement officials figure out “the strategies that the crime syndicates are using to kill elephants and ship illegal ivory,” Wasser says. Adds Wittemyer: “It adds a piece of hard data to a puzzle we’ve been trying to put together in the dark.”