VOA标准英语2009年-Scientists Use DNA to Trace Illegal Elepha

Scientists are using DNA 1 to trace illegal ivory from slaughtered 2 elephants to its countries of origin in an effort to nab poachers. Researchers are trying to combat the multi-billion dollar criminal enterprise at its source.
　
A poached elephant

Since enacting 3 the U.N. treaty outlawing 4 the hunting of endangered elephants for their tusks 5 in 1989, experts say illegal poaching of African elephants has only increased. The illicit 6 ivory trade has been a bonanza 7 for international crime syndicates, with the prized tusks fetching as much as $1,800 per kilogram on world markets.

Demand for ivory has been especially high in China. There is also a substantial market for illegal ivory in the United States and in Japan, where it is commonly fashioned into handles for knives and swords.

To combat poaching, scientists are using the genetic 8 material from the tusks of slaughtered elephants to trace the ivory back to the countries where it originated. They have developed a method for extracting DNA from tiny samples of ivory given to them by authorities in countries where tusks have been confiscated 9.
　
Another poached elephant

That DNA is then compared to a catalog of unique DNA samples taken from elephant dung in regions throughout Africa.

The head of the Center for Conservation Biology at the University of Washington in Seattle, Samuel Wasser, says researchers have pinpointed 11 the origins of thousands of kilograms of illegal ivory smuggled 12 out of Africa, and their evidence makes clear the terrible impact poaching is having on endangered wild elephant populations:
　
An ivory market in central Africa

"People thought the only way they are getting that much ivory is by essentially 13 cherry picking across Africa; going and taking a little from this dealer 14 and that dealer, etc., pulling it together in a common location and shipping 15 it out," said Samuel Wasser. "And what we showed is that for these large seizures 17, that is not what is happening. What is happening is that they ... are all coming from pretty much the same location. So, they are hammering this population [of elephants] over and over and over again, and it looks like the big dealers 18 are putting out purchase orders, saying I need this many cuts by this date, and then they go and hammer this population over and over to get it to them."
　
An adult and a young elephant smelling the femur bone of a dead elephant

Wasser says DNA fingerprinting 19 helped investigators 20 three years ago to make the largest seizure 16 of illegal ivory since the global trade ban went into effect in 1989 - 10 tons of ivory contained in two separate shipments. All of the ivory was traced to a small area near the border of Tanzania and Mozambique.

Wasser says illegal ivory is usually shipped to a number of countries before reaching its final destination in order to avoid detection and protect international dealers.

But the use of DNA, according to Wasser, makes it possible to pinpoint 10 precisely 21 where the ivory comes from when it is finally seized so efforts can be made to stop poachers.

"It allows us to direct limited law enforcement resources to key areas," he said. "It also tends to expose countries in denial [about] the amount of poaching going on in their country and to essentially encourage them to get more serious about policing the illegal trade."

An article on the use of DNA fingerprinting to combat the illegal ivory trade, by Samuel Wasser and fellow researchers at the University of Washington, appears in the July issue of Scientific American.