Large numbers of opium poppy plants grow in the mountains of Myanmar's Shan State.In fact, Shan State is the second-largest opium-producing area in the world.After a drop in production during the 2000s, the number of poppies has risen in the past eight years.Some experts have linked the increased production to a growing demand for the drug heroin in China.But Myanmar's poppy farmers are now earning less on their crops.Now, the United Nations is hoping many will decide to grow coffee instead.For years, thousands of Shan State farmers have earned more profit from sales of opium poppy than from other crops.But poppy prices fluctuate; they may rise one month, but fall the next.Fifty-four-year-old Long San is a poppy farmer.He was one of 400 growers who last year joined a U.N.-supported crop replacement program. Long San is now growing coffee.So far, Myanmar's efforts to cut down on poppy growing have done little to stop the farmers.A U.N. study found that more than 57-thousand hectares of poppy were grown in Shan State last year.