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.