Global Warming Killing Yellow Cedars in Alaska and Canada

A stand of dying Yellow Cedars. Photo courtesy: © Paul Hennon

For the past hundred years, the only name for the plague killing off economically valuable yellow-cedars has been "yellow-cedar decline." The die-off has affected about 60 to 70 percent of the yellow cedars in forests covering 600,000 acres (240,000 hectares) of the North Pacific Coastal Rainforest in Alaska and neighboring British Columbia.

Yellow cedars grow slowly, many reaching ages between 700 and 1200 years old. The wood of the yellow cedar serves Native Alaskans for crafting goods such as paddles, masks, and dishes. With a straight grain, durability and insect-resistance, yellow cedar wood also sells into the home and boat building markets.

Scientists and foresters of the Alaska Region of the Forest Service needed to understand the cause of the die-off in order to plan a conservation strategy. A paper published in the current issue of BioScience sheds light on the mystery, crediting long-term, multidisciplinary research for the findings. Co-publisher Paul Hennon of the Pacific Northwest Research Station explains in the press release on Yellow cedar dying in Alaska:

The cause of tree death, called yellow cedar decline, is now known to be a form of root freezing that occurs during cold weather in late winter and early spring, but only when snow is not present on the ground. When present, snow protects the fine, shallow roots from extreme soil temperatures. The shallow rooting of yellow cedar, early spring growth, and its unique vulnerability to freezing injury also contribute to this problem.

Current predictions foresee less snow overall, but continuing periods of freezing weather in the area, expected to worsen the threat to yellow cedars. The paper concludes that "conservation and management activities need to follow the shifting snow patterns on the landscape." This suggests foresters should deliberately grow yellow cedar forests into favorable directions, nudging the forests towards areas with deeper snowfall.