31 January 2011 Last updated at 14:14 ET
By David Loyn
BBC international development correspondent
Afghanistan produces 90% of the world's opium, the main ingredient in heroin.
The growing of opium poppies in the Afghan provinces of Helmand and Kandahar is predicted to be down for the second year running.
But a UN drugs forecast released on Monday says that poppy growing will increase elsewhere in Afghanistan.
Forecasting the Afghan crop is a tricky business, and the groundwork for this UN survey is based on the sample of only a few villages in each province.
But matched with satellite imaging, it suggests poppy growing will spread.
And that spread this year will even extend into provinces that had become poppy-free in recent years.
The United Nations Office on Drugs and Crime (UNODC) has expressed concern in particular about a predicted increase in Nangahar, a large province bordering Pakistan where poppy growing had been all but eradicated in recent years.
It is a strange market that does not conform to usual market forces.
Although the price to farmers more than doubled last year to $164 a kilogram - because of a cut in output caused by crop disease - the price paid by buyers abroad did not go up.
When you see more conflict, when you see more poverty, you will see more opium cultivation”
So Afghanistan's drug barons were squeezed in the middle.
The higher prices paid to farmers played a big part in encouraging more to plant this year.
The UN survey predicts more planting across a wide swathe of central Afghanistan - from Herat and Ghor in the west to the provinces east of Kabul along the Pakistan border.
Their forecast for the northern region will come out later in the year, as the season starts later in the north.
The predicted rise in poppy planting tallies with other evidence suggesting that the Taliban insurgency has spread across a wider region of the country.
The UNODC's head in Kabul, Jean Luc Lemahieu, said tough measures were needed so that the forecast did not become a reality.
"When you see more conflict, when you see more poverty, you will see more opium cultivation. That is why we continue saying this is not business as usual. We need to put extraordinary measures in place today," he said.
The silver lining in the forecast is that for the third year running, Helmand's crop is forecast to reduce this year - and for the second year, Kandahar too will grow fewer poppies.
These two provinces are by far the largest poppy-growing regions in Afghanistan - accounting for more than a third of the world's opium between them.
The surge of US troops along with British troops in the main population centres in Helmand played a big part, as did weather conditions - too cold and dry at the time farmers wanted to plant.
But the deputy head of the British mission in Helmand, Leo Tomlin, said the forecast showed that a set of policies were working.
They include public information, strong leadership from the Governor Gulab Mangal, tougher policing and better job opportunities.
"It's almost an aligning of the stars. That's also why counter-narcotics takes a long time. It's not something you can start one year and expect to see immediate results," he said.
"It's something that needs a long-term investment, a continued investment with a very similar type of predictable programme."
Even these predicted reductions will leave more than 65,000 hectares under cultivation for poppies in Helmand and some 25,000 hectares in Kandahar.
It may have been pushed onto marginal land, out of sight, but it still remains a potent threat to stability and security in Afghanistan.
Click to view image: 'd8d086799614-heroin_512x512.gif'
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