Chasing poachers, with a little help from the unfriendly atom
Between 1945 to 1980, testing atomic bombs in the atmosphere was a dangerous experiment in spreading carcinogens literally to the four winds. But little noted outside science, the radioactive elements created in the tests became radiologic calendars waiting to be used in any organism that incorporates carbon.
Carbon-14 was one of the many radioactive isotopes formed during the instant of nuclear fission and fusion. An atom of C-14 has two more neutrons than the common C-12.
Because both isotopes are chemically identical, they enter the same biological reactions. And since C-14 decays over time, the level in the sample can be traced back to the high level of C-14 in the air during the atom-bomb tests. The result shows when a living animal was eating food contaminated with bomb fallout.
This technique, called carbon dating, was traditionally used to date archeological sites from long before the nuclear era. Now, the “bomb-pulse” of radiation allows organisms from the modern era to be dated, which could one day identify illegal ivory.
A study published this week shows the potential for carbon-dating teeth and ivory tusks from elephants. Thure Cerling, a professor of geology, geophysics and biology of the University of Utah, an expert on carbon dating, was interested in dating ancient bone and ivory samples from Kenya.
To explore how carbon had entered the material, Cerling and graduate student (and now Ph.D.) Kevin Uno started with modern elephants. In collaboration with Wildlife Kenya, Cerling says, “We were putting GPS collars on the elephants, and I had tools to help them understand what the elephants were eating, using isotopes as traces.”
In the mid-2000s, after an animal they were tracking died, Kenya Wildlife gave permission to examine the tusks. “We weren’t really thinking of ivory poaching,” Cerling says. “We were interested in how the molar teeth and ivory incorporate isotopes, but as we were doing the study, poaching got worse, and it was quite clear that this could also address the poaching problem.”
Ivory trade on the rebound
By the 1990s, market restrictions, international law and social attitudes had brought a steep decline in the demand for ivory in the principal markets of North America and Europe. “It very quickly became socially unacceptable to have ivory,” says Cerling .”
Now that people in China and Southeast Asia can afford ivory, elephant killings, corruption and illegal export are booming. By the end of 2011, “illegal ivory trade activity has more than doubled since 2007, and is now over three times larger than it was in 1998,” according to CITES: the the Convention on International Trade in Endangered Species of Wild Fauna and Flora.
Elephants can live 40 or 50 years, and the tests cannot always pin down exactly when the elephant lived. But CITES broadly proscribes certain dates, so the technique may be accurate enough.
Noting that several tons were seized just last week, Cerling says “The important question is whether these were killed last year, in which case, somebody is actively killing, or some government in Africa has been stockpiling ivory over the years and somebody is getting their hands on the stockpile. We could tell the difference — and the enforcement issues would be very different.”
One part in a trillion!
C-14 can be tracked by an instrument called the mass spectrograph, but because C-14 is only present in part-per-trillion quantities, the new analysis will not work on a dollar-store mass spec.
In the United States, at most a half dozen labs could do this, Cerling says.
Although it’s not especially cheap, costing about $500 per analysis, Cerling notes that a recent seizure nabbed 40 tons of ivory, with a $100 million street value. “So the cost is very small compared to the size of the problem.”
Cerling and Uno suggest the same dating process could be used to clamp down on poaching of rhinoceros, which faces extinction due to slaughter for their prized horns.
Although carbon dating had been suggested as an anti-poaching tactic and “People had assumed it works, it had not been done,” Cerling says.
Cerling, who is more than happy to aid the fight against poaching, stresses how the study sprouted from basic paleontology. “We needed to understand how things work in the modern situation first; it’s a beautiful demonstration of how science cuts across different disciplines. With science, you don’t know where it is going to lead.”
— David J. Tenenbaum
Terry Devitt, editor; S.V. Medaris, designer/illustrator; Yilang Peng, project assistant; David J. Tenenbaum, feature writer; Amy Toburen, content development executive
- Bomb-curve radiocarbon measurement of recent biologic tissues and applications to wildlife forensic and stable isotope (paleo)ecology, Kevin T. Uno et al, PNAS early edition, July 2013, www.pnas.org/cgi/doi/10.1073/pnas.1302226110. ↩
- [Video] How carbon dating works ↩
- Carbon dating can determine the vintage ↩
- Blood ivory: Butchering in Chad and worship in Cebu ↩
- [Video] The history of the ivory trade ↩