Low snow a boon, burden

Thin snowpack helps moose but can harm plants, fish, other organisms

Posted: Tuesday, February 21, 2006

 

  A young moose browses through shallow snow in Kenai last weekend. A mild winter helps some animals but makes life more difficult for others. Photo by M. Scott Moon

A young moose browses through shallow snow in Kenai last weekend. A mild winter helps some animals but makes life more difficult for others.

Photo by M. Scott Moon

Low snow depths have frustrated winter recreation enthusiasts on the Kenai Peninsula and elevated concerns about the upcoming Arctic Winter Games, but the impact of low snow depths on peninsula ecosystems has received less attention.

Although overall precipitation this year has not strayed far from long-term averages, snow depths below tree line levels have, impacting organisms that range from the size of a moose to the smallest creatures in the soil.

“I know that this year is definitely low,” said Ben Balk, a hydrologist for the Alaska Pacific River Forecast Center.

This winter, the climate on the peninsula has vacillated between warm and wet and cold and dry, providing few opportunities for snow to accumulate and beating back the bit of snow that has accumulated with rain and above-freezing temperatures, he said.

For moose the low snowpack is mostly a boon, exposing vegetation for them to munch on and making it easier for them to walk around.

“If you’ve got three feet of snow, that’s really hard on the little guys,” said Ed Berg, a Kenai National Wildlife Refuge ecologist.

Less snow typically means fewer moose strolling on highways where they wearily amble to escape exhausting treks through deep snow but frequently die in collisions with motor vehicles.

A look beneath the snowpack, however, reveals a slew of organisms that have evolved to depend on a hefty layer of snow for protection and to insulate them from extreme cold and unusual warm spells.

Under a layer of snow, for example, plants are less likely to prematurely break their dormancy, an event that can lead to a false spring and potentially great vegetative damage if warm temperatures are followed by a cold snap.

In the winter that began in 2002, for example, low snow depths combined with warm temperatures and a cold snap resulted in a brown spring on much of the peninsula, Berg said. From mid-January through March 2003, little snow cover and two months of unseasonably warm weather triggered plants to break their dormancy and begin new growth. The early growth spurt would not have been a problem had temperatures remained warm, but they didn’t.

Instead, a blast of cold air replaced warm temperatures, killing off new growth and turning the underbrush brown, most noticeably a plant known as Labrador tea, he said.

Even if air temperatures rise to 40 degrees, plants packed in snow can remain insulated in a snowy cocoon of dormancy.

But as long as uncovered plants are not exposed to a warm spell followed by icy-cold temperatures, Berg said he does not expect this year’s low snow depths to create problems for plants.

Other members of the ecosystem also depend on deep snow layers for protection. Small mammals that remain busy and active during the winter, such as voles and shrews, use snow to create snow tunnels, without which they can be exposed to predators.

And microbes responsible for composting nature’s waste into soil may slow when normal snowpack levels do not develop to shield them from the cold.

“The warmer the soil, the more microbial activity,” Berg said.

A normal snow depth also promotes healthy salmon runs, according to Larry Marsh, an area management biologist with the Alaska Department of Fish and Game Sport Fish Division.

The snowpack acts like a bank account, accumulating precipitation over the winter and discharging it into streams in one large sum in the spring.

Without this large discharge, salmon fry and eggs located in more marginal, shallow areas can die, Marsh said.

“Those will be more at risk with low water levels,” he said. “If there is no flow ... those eggs are not going to be viable.”

Salmon depend on two periods of peak water levels, one in the spring and one in the summer.

“They’ve optimized to take advantage of that,” Marsh said.

The spring peak depends heavily on snowmelt, since spring months typically receive little rainfall and temperatures are not yet warm enough to melt large amounts of glacial water, he said.

That does not mean, however, that this spring’s water levels couldn’t receive a boost from unusually heavy rains, he said.

If current trends continue, organisms that benefit from or can adapt to the consequences of low snow levels may win out.

Although precipitation levels have not necessarily been falling in recent years, the number of warming events beating snow depths down seem to be on the rise.

“They seem to be a little more frequent,” Balk said. “(In) the last few years we have been battling with these quite a bit.”

Berg said Balk’s observations on increased warming events generally correlate with his own.

“That would be my barstool observation,” he said. “It seems like we get many January thaws ... but that’s just my off-the-cuff observation.”



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