Mt. Rainier Studies Confirm Encroachment Of Forests Into Meadow Since 1930s, Thanks To Temp Changes

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Nothing lures visitors to Paradise like the transitory displays of wildflowers that populate Mount Rainier’s high mountain meadows.
But summer sojourns could fade into memory and panoramic vistas vanish as alpine asters, rosy pussytoes and purple lupines are crowded out by trees. Add disappearing high mountain meadows to the catalog of effects wrought by global warming. “There aren’t very many places where you can visually identify the changes affected by climate. This is one,” said David Peterson, a U.S. Forest Service research biologist.

The problem is snowfall, or more precisely, the lack of it. A long-term decline in mountain snowpack – also to blame for many shrinking glaciers – permits trees to grow in places where they couldn’t otherwise establish a foothold. “As soon as you get less snow, there are more opportunities for trees to come in,” said botanist Regina Rochefort, a National Park Service science adviser.

Plant ecologist Mignonne Bivin, Rochefort’s Park Service colleague, put it this way: “Meadows stay open because of snowpack. That’s what restricts trees – temperature and water availability. As we get less snow and more rain, we get more trees.” Rochefort began exploring the pattern of tree encroachment at Mount Rainier in the early 1990s. Her research focused on subalpine meadows at elevations between 5,000 and 7,000 feet above sea level.

It’s the transition zone, where forests give way to open ground, and also below the treeless alpine areas, where snow persists year-round. This is a battle zone, where trees compete for space with other species, said Peterson, who advised Rochefort on her research. The study was the subject of a 1996 article in the journal Arctic and Alpine Research. “It’s definitely going from meadows to forests,” Rochefort said. “These are dynamic landscapes. They are changing, but none of us really expect it to change in our lifetime.”

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