Tracking Illegal Ivory: the Forensics

The atmospheric carbon left over from nuclear bomb testing could help scientists track poached ivory, new research has found.  These bomb tests changed the level of carbon in the atmosphere, which can be traced to date elephant tusks…Scientists say the findings, published in PNAS, could make it easier to enforce the ivory ban.The number of elephants being poached is now at the highest it has been for two decades, according to a UN backed report.  This was highlighted in January when a family of 11 elephants was slaughtered in Kenya, their tusks hacked off with machetes.

Traditional radiocarbon dating determines the age of ancient objects by measuring the amount of carbon-14 (C14).  The approximate time since an organism died can be measured from the amount of C14 left in its remains. But remains from after the Cold War contain higher levels of C14 due to the nuclear bombs.  In a new study Dr Uno and colleagues used this increase in carbon to date herbivore samples, which they matched to corresponding points on the bomb-curve

In the 1980s, more than half of Africa’s elephants are thought to have been wiped out by poachers. This led to an international ban on trading ivory in 1989….Scientists have found that radioactive carbon in the atmosphere emitted during the Cold War bomb tests will make it easier to distinguish between illegal ivory–that acquired after the 1989 ban– and legal ivory– that acquired before the 1989 trade ban.  The amount of radiocarbon in the atmosphere nearly doubled during nuclear weapons tests from 1952 to 1962, which steadily dropped after tests were restricted to underground. This has been dubbed “the bomb-curve”.

The levels have declined since but as they are still absorbed by plant, they enter the food chain and are measurable in plant and animal tissues.  The concentration of radiocarbon found in tiny samples of animal tissue can accurately determine the year of an animals death, from 1955 until today, Kevin Uno from Colombia University, US, explained to BBC News.  “This is different to the traditional dating technique which takes advantage of the loss of radiocarbon through time.”  Traditional radiocarbon dating would only be able to pick up an “imperceptible amount of decay” added Dr Uno, but because the bomb spike doubled the concentration or carbon, they were able to find huge variations over the last 60 years, which enabled accurate dating.Dr Uno said this technique “would dovetail very nicely with DNA testing which tells you the region of origin, but not the date”.  As anti-poaching funding is extremely limited, understanding where the poaching hotspots are, as well as how old the tusks are, could help the international community to direct funding to the places most at risk, he added…

These wildlife forensics are ready to roll, now we need to speak to the organisations who can set up a programme to make it happen.”

Excerpts, Melissa Hogenboom, Carbon from nuclear tests could help fight poacher, BBC News, July 1, 2013

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