Nuclear fallout from atomic bomb tests conducted decades ago could help track down poachers by accurately dating when animals were killed. Carbon released into the atmosphere by above-ground nuclear tests between 1952 and 1962 can be traced in ivory products long after the demise of the animal.
During that decade, the amount of carbon 14 (C14) in the atmosphere doubled. That concentration lowered soon after most nuclear-armed nations agreed to end nuclear tests above ground, but traces of it still exist in plants and the animals that eat them. This rise in C14 during those ten years is known as the "bomb-curve."
"Most of the original nuclear weapons testing was done in the U.S. and the Soviet Union at about latitude 40 to 60 degrees north. It took about a year-and-a-half to two years to mix all that carbon 14 across the equator." Thure Cerling, a geochemist from the University of Utah who was lead author of a study announcing the results, said.
By measuring the levels of C14 in tissue samples, Kevin Uno, from Columbia University, found a way to determine the year any animal died, from 1955 to today. Traditional carbon 14 dating involves measuring the decay of the isotope in the target material. The amount of this decay over the last 50 to 60 years would be insignificant, rendering the technique useless. But comparing the concentration of C14 to the bomb-curve levels gives researchers a guide to accurately measure when the animal perished.
"The year an elephant died plays a big role in whether or not the trade [of ivory] is legal. Poached ivory makes it to market relatively quickly, so by measuring the age of a tusk we can say what year it's from. This will help us pinpoint the source of the ivory and how it's getting to market," Uno said.
During the 1980's over half of the elephants which lived in Africa were killed by poachers, looking to harvest their tusks for ivory. Due to this, an international ban on trading ivory was adopted in 1989. Soon, demand for products made of the material also declined. However, this demand is once again beginning to climb in Asia, especially China, fueling a recent rise in the number of elephants poached. In January 2013, the bodies of 11 elephants were found in Kenya with their tusks cut off.
The study was conducted on 29 samples from herbivore animals and plants, collected between 1905 and 2008 in East Africa. Animal parts tested included horns, teeth, tusks, hair and soft tissues.
According to the United Nations, approximately 17,000 elephants were killed for their tusks in 2011. The poaching of ivory is being increasingly used to help fund civil wars.
It is possible that a similar technique, comparing C14 levels to the bomb-curve, could help identify human remains and recognize forged works of art.
Study into dating ivory through the measurement of carbon from nuclear tests was published in the Proceedings of the National Academy of Sciences of the United States of America (PNAS).