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Nailing poachers with radiation

Author Jacqueline Detwiler Illustration James Provost

brightideas

You rarely hear folks praise nuclear radiation these days, but Kevin Uno—a postdoctoral research scientist at Columbia University who has a bone to pick with ivory poachers—is doing just that. After World War II, when the U.S. and the Soviet Union started testing nuclear weapons, the atmospheric levels of an unstable isotope known as carbon 14 shot up dramatically, peaking in the mid-’60s, and then fell steadily in a pattern known as the “bomb curve.” Carbon 14 is the same isotope that has been used in carbon dating techniques for years, but with this bomb curve—linked to historical records—the ages of plants and animals that died within the last 60 or so years can now be estimated with greater accuracy. With poaching on the rise in recent years and criminals claiming that they’re selling ivory only from elephants hunted years ago, Uno hopes to use his bomb-curve dating technique to determine the real age of elephant tusks and catch the traffickers in the act. Here’s how he’ll do it.

  1. Luckily for researchers, there’s lots of carbon in collagen, one of the primary materials in a tusk. To measure the carbon 14, the scientists collect a tiny amount of ivory—less than a pinch of salt—burn it to release carbon dioxide, and then turn that carbon dioxide into a carbon pellet. A lab then estimates how much of the carbon in the pellet is carbon 14.
  2. Because the bomb curve is, well, a curve, many carbon 14 levels can correspond to two different ages—the year on the way up the curve, and the year on the way down. How can scientists tell the difference? Tusks grow outward, so by testing an older sample at the tip of the tusk and a younger sample at the base, they can tell whether carbon 14 was rising or falling while the tusk was growing.
  3. Finally, Uno and his colleagues are hoping to collaborate with another scientist who focuses not on when elephants were killed, but where. Together, they would analyze DNA to find out which population the elephant came from, and carbon to find out when it died. The combination of information would lead to knowledge about poaching hotspots, and hopefully crackdowns.

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