Researchers use genetic map to track down source of illegal ivory

· Revolutionary technique deals blow to poachers
· 20,000 elephants a year killed as prices soar

Scientists have traced a multi-million pound haul of ivory products to its origins on the African savanna using a revolutionary genetic map of elephant herds on the continent.

The shipment of more than 6.5 tonnes of contraband tusks and ivory stamps was seized in Singapore after being packed into a 6m (20ft) container in Malawi and sent to the far east via South Africa.

Using the map, researchers working with investigators from Interpol tracked the ivory to a narrow band of southern Africa, centring on Zambia.

The investigation is the first time the map has been used to identify the source of an illegal haul of ivory and deals a significant blow to the trade, which has seen market prices soar from $100 (£51) a kg in the late 1990s to $750 a kg last year. The dramatic rise has raised concerns that commodity speculators are now buying up ivory to cash in when prices peak.

The map was constructed by scientists who extracted DNA from the tissues and dung of elephants in different regions, from the dense forests of western and central Africa to the vast savanna. The scientists identified genetic signatures belonging to each of the populations, which they later matched to the confiscated ivory products.

The contraband, which was seized in June 2002, represents the largest haul to be intercepted since a broad trade ban was introduced in 1989. The container held 532 tusks, each weighing on average more than 11kg, suggesting they were cut from older elephants. A further 42,120 thick ivory cylinders called "hankos" were also recovered. In some Asian communities hankos are carved with personal seals and used as prestigious stamps.

The value of the hankos alone has been estimated at $8.4m, amounting to around 20% of Japan's annual trade in the seals. Researchers estimate the entire haul resulted from the poaching of 3,000 to 6,500 elephants, according to the study published in Proceedings of the National Academy of Sciences.

Investigators originally believed the ivory was smuggled into Malawi mainly from the forested regions of Africa. But researchers lead by Samuel Wasser at the University of Washington in Seattle conducted DNA tests on 67 of the tusks and found they matched elephants roaming a band of land across Zambia, and possibly regions of Mozambique and the Angolan savanna. The tests were possible only after painstakingly working out how to remove calcium from the tusks without harming the fragile genetic material.

"Until DNA came along you'd always follow the paper trail, looking at shipping documents, who leased containers and so on, and you could almost always get back to the point of export. Now we can trace it back beyond export to the point of poaching, where the original crime is committed," said Bill Clark, a wildlife law enforcement expert and co-author of the paper.

"This gives enforcement officers information on which populations are being hit and so where they need to invest their resources. It's a very timely development, because poaching has intensified dramatically in recent years."

The technique is now expected to be used to track more hauls back to their countries of origin.

Researchers believe that around 20,000 elephants are killed by poachers each year, four times the number slaughtered three years ago. A poacher in Africa may earn $400 from ivory taken from one elephant, compared with a park ranger's monthly salary of less than $60. Last year nearly 24 tonnes of ivory were seized, but experts believe that represents only one tenth of all illegal ivory trade.

"We need tighter controls along the whole chain that leads from Africa to the markets, and that involves poaching, smuggling and usually corruption. But ultimately, terminating the fashion for ivory is the only thing likely to save the elephants," said Dr Clark.