KABUL (Reuters) - Opium cultivation in Afghanistan fell by 22 per cent this year as prices for the drug tumbled causing farmers to switch to other crops, the United Nations said on Wednesday. Some 1.6 million Afghans (6.4pc of the population) are involved in the illegal drugs trade compared to 2.4 million last year, according to an annual UN report, a rare bit of good news for Western efforts in the country. The bottom is starting to fall out of the Afghan opium market. These results are a welcome piece of good news and demonstrate that progress is possible, said UN Office on Drugs and Crime (UNODC) Executive Director Antonio Maria Costa in the report issued on Wednesday. This year, 123,000 hectares were used to grow opium poppy, compared to 157,000 hectares in 2008, the UNODC said. Despite cultivating just 78pc as much land, Afghan poppy farmers still produced 90pc as much opium as last year, because of record yields caused in part by good weather. The 6,900 tonnes of opium Afghanistan produced is far more than the 5,000 tonnes the worlds addicts consume, leading to a glut that has depressed prices to lows unseen since the 1990s. There are stocks ... in south of Afghanistan, certainly in Pakistan and elsewhere. These stockpiles could be a very important way of funding terrorism worldwide, not only in the region, Costa told Reuters. Most of the reduction took place in the countrys most violent province, Helmand, the opium growing heartland and main focus of US and British war efforts. Cultivation there fell by a third to 69,833 hectares, from 103,590 hectares in 2008. The fall in price drove the total value of Afghanistans opium crop down 40pc to $438m. Opium now makes up just 4pc of Afghan GDP, compared to 7pc in 2008 and a record 27pc in 2002, a year after the Taliban were ousted. All of that has created stocks, an excess supply, and on the whole has driven conditions such that it has become less and less attractive for farmers to cultivate opium, Costa told Reuters. Still, Costa said it was too early to tell whether the decrease in cultivation and production over the past two years is a market correction that could be reversed, or a downward trend. The crash seems to be a result of simple economics, rather than law enforcement efforts. Only 4pc of the crop was eradicated and 2pc of the harvested product was seized. Last year food prices soared even as opium prices tumbled. Where farmers could earn 27 times as much per hectare growing opium as growing wheat in 2003, and 10 times as much in 2007, since last year, they have been able to earn only three times as much, no longer necessarily worth the extra effort and risk. Despite the decline over the past two years, opium cultivation has soared since the Taliban were overthrown in late 2001. Cultivation under the Taliban peaked in 1999 with 91,000 hectares, less than half the amount grown in 2007. In 2001, just before the Taliban were removed from power, opium cultivation plummeted to 8,000 hectares when the militants imposed a ban on growing the drug the year before.