Trees Suffer One-Two Punch of Acid Rain and Climate Change

Forests in Vermont's Green Mountains transition abruptly from a heat-loving mix of sugar maple, American beech, and yellow birch on the lower slopes to a cold-adapted mix of red spruce, balsam fir, and paper birch higher up.

A new study shows that the altitude of that transition zone rose as much as 400 feet between 1962 and 2005-right in sync with a hike of 2 Fahrenheit degrees in the area's mean annual temperature.