DAVID GREENE, HOST:
President Obama is finishing up his visit to Africa today. On his third stop, Tanzania, he announced a new program to combat the poaching of endangered species, like elephants. A rapid rise in the price of elephant ivory has seen the slaughter of elephants reach its worst levels in decades, and poachers are becoming increasingly sophisticated in how they operate.
As NPR's Christopher Joyce reports, that has inspired scientists to devise new methods to catch them.
CHRISTOPHER JOYCE, BYLINE: A pound of ivory is now worth more than a thousand dollars. Wildlife experts attribute the rise in price largely to consumers, especially in Asia, with new money to spend on ivory carvings. Trying to stop the trade is messy. Different countries banned ivory trade at different times. Some ivory taken before those bans may be legal to trade. And there have been a few legal sales of stockpiled ivory over the past decade. So it's hard to tell if a piece of ivory in a shipping container or someone's bookcase is legal or not.
That's something geochemist Kevin Uno is trying to fix. At the University of Utah, Uno worked out a way to date a piece of ivory by measuring how much radioactive carbon is in it.
KEVIN UNO: We use the adage you are what you eat in the type of work we do.
JOYCE: Here's how it works: Nuclear bomb tests in the '50s and '60s pumped a lot of radiocarbon into the atmosphere. It went everywhere, including into plants that animals - like elephants - eat. Since bomb testing ended in the 1960s, that radiocarbon has been slowly dwindling. Scientists can chart its decline year by year. So a leaf in Africa in, say, 1990 had a different radiocarbon flavor, if you will, than one in 2010 - kind of how wines differ by vintage.
UNO: And an elephant comes along and eats that leaf. Well, that leaf has essentially locked in the concentration of radiocarbon from the atmosphere.
JOYCE: Then some of that radiocarbon goes into the elephant's tusk.
UNO: Once it's fixed in the tissue in the tusk or the hair, it's locked in.
JOYCE: At the bottom end of a tusk - the wide, fat part - is the crucial date, the year the tusk stopped growing, the year the elephant died.
George Wittemyer collaborated in the research. He's a conservation biologist at Colorado State University.
GEORGE WITTEMYER: The dating can be very effective in terms of indentifying if the tusks are all from a relatively recent time. For example, if all those elephants were killed in the last year, that would be indicative that this ivory is indeed from very contemporary poaching.
JOYCE: And not, as illegal traffickers commonly claim, from older ivory that was harvested before trade bans were put into effect. In fact, poachers sometimes artificially weather or age ivory to make it look old, from pre-ban times. Radiocarbon dating theoretically could see through that deception.
Recently, scientists have successfully used another high-tech tool to determine where ivory comes from: DNA from a tusk, as well as some chemical isotopes, can indicate what elephant population it's from, say, northern Tanzania versus South Africa. Knowing where an elephant lived and when it died would help determine if it was taken before or after a ban in that country.
Richard Ruggiero has monitored wildlife trade in Africa for decades, most recently with the U.S. Fish and Wildlife Service. He says traffickers are increasingly part of well-organized, well-funded syndicates, using ivory much the way groups once used blood diamonds.
RICHARD RUGGIERO: They do a risk-benefit analysis, risk being the probability of being detected. A tool, like the one we're talking about, would make prosecutions easier, and therefore raise the risk part of that risk-benefit analysis.
JOYCE: The research appears in the latest proceedings of the National Academy of Sciences.
Christopher Joyce, NPR News.