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.