Glacier Park's climate a paradox

Precipitation in Glacier National Park over the past few decades is up about 14 percent, but the Park is actually drier in many respects, with streams hitting low flows earlier than usual and wildfires occurring more frequently.

How can that be? Trees, U.S. Geological Survey scientist Dan Fagre explained at a recent talk in Apgar. While the Park may be wetter, it's also warmer. And with warmth, there's been less snow on average than in the past, he said.

With less snow, the treeline in Glacier Park has slowly but surely moved higher in elevation. And with more trees growing in the Park, there is more evapotranspiration, Fagre said. The trees draw water out of the ground and release it into the atmosphere, creating drier conditions, particularly in late July and August.

Hotter, drier conditions in the summer months result in more wildfires. That reduces the tree population for a few years, but then they grow back, and there's evidence to suggest that new trees grow faster than old trees.

A warmer and wetter Park also has an impact on animals, insects and other plants, Fagre noted. The meltwater lednian stonefly lives exclusively in the cold clean waters in streams below glaciers. As glaciers continue to melt, the stonefly could go extinct.

But it's not just about glaciers. It's also about something far more common in the Park - snowfields. Large snowfields also provide unique habitat for different plant species, including the pygmy poppy, which grows in poor soil just below melting snowfields.

There is also concern that as snowfields grow smaller and melt faster, there could be impacts to one of the Park's most unique carnivores - the wolverine. The wolverine dens under mid-level snowpacks where it can safely rear its young and remain unharmed by other larger predators.

In addition to the wolverine, snow packs also protect the Park's pika population. The deep snow covers talus slopes where pikas live, providing insulation from the cold. If the Park has cold with no snow, pikas can't survive.

Even last winter's large snowpack had little overall impact on the Park's glaciers, Fagre noted. While there was a net increase in snow mass on the glaciers, it was greatly diminished by one of the mildest and driest Septembers on record.

Over the past 10 years, the Park's glaciers have continued to shrink at a rapid rate, Fagre noted.

But some glaciers in the U.S. are growing. Mount Shasta in California has growing glaciers because it receives more precipitation and is still cold enough to produce snow.