As Russia’s enormous boreal forest undergoes rapid warming, a significant shift in tree species is occurring, with evergreen trees such as spruce and fir creeping poleward as the iconic tree of Russia’s far north, the larch, is in decline, according to a new study. 
Researchers at the University of Virginia said the shift is expected to further hasten warming because of a fundamental difference between larch trees and evergreens. Larch is a species of conifer, but in the fall it sheds its golden needles, allowing sunlight to shine through the tree’s bare branches and reflect solar radiation off the snow and back into space, further cooling Russia’s northern regions. But as more warmth-tolerant evergreen species spread north, these trees — which do not shed their needles — absorb heat and increase temperatures, according to the research, published in Global Change Biology. The shift in species thus acts as a so-called positive feedback, further warming the region. This cycle of temperature increases could hasten the melt of permafrost, releasing large amounts of methane and CO2. “What we’re seeing is a system kicking into overdrive,” said Hank Shugart, professor of environmental sciences. “Warming creates more warming.”
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