US researchers say climate modeling predicts a much greener arctic in the coming decades with more trees and shrubs because of global warming. Rising temperatures will lead to a massive "greening" of the arctic as plant cover and wooded areas could increase by as much as 50 percent, they said. This increase has already been occurring in the past few decades as average temperature in the arctic has been rising about twice the global rate, Richard Pearson of the American Museum of Natural History's Center for Biodiversity and Conservation said. "Such widespread redistribution of Arctic vegetation would have impacts that reverberate through the global ecosystem," he said, Ongoing temperature increases could bring massive redistribution of vegetation across the arctic with about half of all vegetation switching to a different class and a massive increase in tree cover, as for example in Siberia where trees could grow hundreds of miles north of the present tree line, a museum release said Monday. "These impacts would extend far beyond the arctic region," Pearson said. "For example, some species of birds seasonally migrate from lower latitudes and rely on finding particular polar habitats, such as open space for ground-nesting." The greening would also introduce a feedback effect, researchers said. When the sun hits snow, most of the radiation is reflected back to space, but when it hits a "dark" area covered in trees or shrubs, more sunlight is absorbed in the area and temperature increases. This has a positive feedback to climate warming, the researchers said: The more vegetation there is, the more warming will occur.