Let's turn the microphone over to the very intelligent Jeffrey Clemens, who is now a Ph.d. student at Harvard I believe:
Recent estimates suggest that in 2007, Afghan opiate production accounted for about 93 percent of the world's total. This article presents a framework for estimating the potential for source country drug control policies to reduce this production. It contains a first pass at estimating the potential for policy to shift the supply of opium upward, as well as a range of supply and demand elasticities. The estimates suggest that meager reductions in production can be expected through alternative development programs alone (reductions are less than 6.5 percent in all but one of the specifications presented). They also suggest that substantial increases in crop eradication would be needed to achieve even moderate reductions in production (reductions range from 3.0 percent to 19.4 percent for various specifications). The results also imply that, all else being equal, the cessation of crop eradication would result in only modest increases in opiate production (with estimates ranging from 1.6 percent to 9.6 percent).
I can't find an ungated copy, can you? In any case, the bottom line seems to be that this problem won't get solved.