 Lush green tea plantations, so bright they often look fluorescent, blanket the hills of assam in northeastern India. Women plucking the leaves in black aprons with large baskets on their backs dot the gardens that contribute to India's production of nearly a third of the world's tea. But this picturesque industry that the British began in the early 19th-century faces a very modern problem: climate change.  Researchers and planters worry that a rise in temperatures and change in rainfall patterns are threatening the production and quality of assam's famous tea.  There is also a fear that environmental changes will affect the quality of the tea by weakening its powerful taste.  "We are indeed concerned," Rajib Barooah, another tea planter in Jorhat, told the associated Press. "assam tea's strong flavour is its hallmark."  about 850 tea gardens in assam produce 55 percent of India's tea, but crop yields are decreasing and amid fears of a correlation with environmental change. Production in the state fell from 564,000 tons in 2007 to 487,000 tons in 2009, and the crop was estimated to have fallen to 460,000 tons in 2010, according to the assam Branch Indian Tea association. "Climate changing is definitely happening," said Mridul Hazarika, the director of the Tea Research association, which is conducting studies on how the changes are hitting tea production. "It is affecting the tea gardens in a number of ways."  In the tea-growing areas of assam, average temperatures have risen C and rainfall has fallen by more than a fifth in the past 80 years. Globally, 2010 was the hottest year on record, according to temperature readings by Nasa's Goddard Institute o 