By Douglas Main
Bomb tests generations ago could indirectly help fight illegal poaching of African elephants, new research shows.
Nuclear weapons tested in the atmosphere in the 1950s and '60s spread a radioactive variety of carbon worldwide, which was picked up by plants during photosynthesis and then deposited in the bodies of herbivores like African elephants. By looking at the levels of this carbon isotope — known as carbon-14 — in elephant tusks and ivory, researchers can find out how old they are. (Isotopes are versions of elements that have differing numbers of neutrons in their nuclei.)
Knowing the age of elephant tusks is important, since many regulations of ivory trade are date-specific. In the United States, for example, ivory taken prior to a 1989 worldwide ban on African elephant tusks may be legally traded, while new ivory is illegal to traffic, said Kevin Uno, a researcher at the Lamont-Doherty Earth Observatory at Columbia University in New York.
"I don't necessarily think this will save the elephants, but it's a critical tool to fight poaching of elephants," said Uno, co-author of a study detailing the technique, published today (July 1) in the journal Proceedings of the National Academy of Sciences.
A critical tool
Atmospheric bomb testing caused a spike in carbon-14 that has slowly declined in the past 50 years. By measuring the concentration of this type of carbon, researchers are given two possible dates for the age of the sample, before and after the spike on the curve of carbon-14 concentrations. To figure out which is the right age, researchers have to sample in two locations on the ivory, said Uno, who performed the research while he was doctoral student at the University of Utah.
Specifically, researchers test one part of the tusk that is younger, and one that is older. They can do this by following the grain of the ivory, which shows which way the tusk grew. This allows them to figure out which of the two dates is the right one, Uno said. More....