Trees overtaking Kenai's tundra diminish alpine habitat for Dall sheep, caribou

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SOLDOTNA, Alaska (KTUU) - Trees and shrubs are rapidly expanding into alpine tundra on the Kenai Peninsula and will force several animal populations to adapt the diminished habitat.

(KTUU)

"We've got rates in the Kenai Mountains of treeline rise one meter per year since 1950, and then you look at shrub rise, it's 2.8 meters per year," said John Morton, Supervisory Biologist at the Kenai National Wildlife Refuge. "That's huge. It's like leaping up the mountains. That's a big deal."

The rising treeline is only one component of a shifting forest system on the Kenai. In addition to growing up mountains, spruce forest is also expanding into areas that were peatlands for thousands of years. Receding glaciers in the Harding Ice Field expose barren rock that will eventually become new alpine tundra, but that process is happening much slower than the tundra is shrinking due to the rising treeline, Morton says.

"One meter per year over 50 years doesn't like a lot, only 50 meters. The thing is if you follow that line in a GIS and you realize how convoluted the Kenai Mountains are and you go in and out of every valley and every ravine, my recollection is I estimated that a few years ago as being 300,000 acres, which is not a trivial amount of alpine tundra to be converted by afforestation," Morton said.

Morton says there is a lot of alpine tundra on the Kenai Peninsula, yet because of the geographic layout of alpine tundra in the Kenai Mountains, the percentage of remaining tundra diminishes increasingly each year.

"Anything that's alpine dependent, here I'm talking about things like ptarmigan, specifically willow ptarmigan, and caribou, Dall sheep - all these kinds of animals that really do need alpine tundra to survive here on the Kenai, we would expect basically, hard times are coming for them," Morton said.

Although the loss of tundra habitat may influence the abundance of alpine animals, Morton says other factors must also be considered.

"It's not just about loss of habitat. They're also experiencing these very, very hot summers now and we're getting heat stressed animals, and that's obviously taking its toll," Morton said.

Although the US Fish & Wildlife Service has data on the increasing treeline dating back to the early 1950s, Morton says its too early to see how the animals will respond to diminishing alpine tundra.

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