Poppy flop: the drug war's high yields.

After a much-ballyhooed effort to cut opium production in Afghanistan, the United Nations says the acreage devoted to poppies has been reduced by one-fifth. Yet opium production is virtually unchanged, and the country still accounts for an estimated 87 percent of the world's heroin.

The explanation appears to be improved productivity. According to the U.N. Office on Drugs and Crime, opium yields per acre rose 28 percent between 2004 and 2005, when opium production barely changed even though the amount of land devoted to poppies dropped from 323,570 acres to 256,880 acres. Something similar seems to be happening in Colombia, where coca eradication efforts reportedly have prompted farmers to use more-productive plant varieties.

Even when crackdowns on drug crops show clearer results, their main effect is to shift cultivation from country to country. History gives little reason to expect that a successful effort to stamp out opium production in Afghanistan would have a lasting effect on the world's heroin supply. And given the economic dislocation and anti-American sentiment that would be caused by a successful attempt to eliminate Afghan opium production, which may account for as much as 60 percent of the country's gross domestic product, perhaps it's just as well that the crackdown has been a bust.

But Antonio Maria Costa, executive director of the U.N. Office on Drugs and Crime, is undeterred. He says opium can be eliminated from Afghanistan within 20 years, a convenient time frame for the 64-year-old bureaucrat. Implausible as that projection is, Costa is a realist compared to his predecessor, Pino Arlacchi. "Global coca leaf and opium poppy acreage totals an area less than half the size of Puerto Rico," Arlacchi said in 1998. "There is no reason it cannot be eliminated in little more than a decade."