Experts say stands of white spruce, which a recent study found contain half of the genetic diversity of all white spruce in North America, are suffering, ScientificAmerican.com reported Wednesday.

"A biome shift is now occurring," University of Alaska, Fairbanks, forest ecologist Glenn Juday said. "You don't have to wait for the effects. They're happening."

North America's white spruce require at least 11 inches of rain each year, a number that rises if mean summer temperatures are higher than around 60 degrees F.

When temperatures hit a mean of just below 70 degrees F, the trees can't survive.

In Fairbanks, conditions are hovering right on that edge. July temperatures have exceeded 70 F several times in the last 20 years, Juday said.

As a result, white spruce growing around Fairbanks are "probably not viable on a long-term basis under such conditions," Juday said. "With each additional degree of warming, their growth goes down."

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