From 2002 to 2009, two moth species defoliated as much as a third of the mountain birch trees that stretch across northern Norway, Sweden, and Finland. By 2014, some trees had recovered (top) while others had not (bottom). Photo: Jakob Iglhaut / Science News
From 2002 to 2009, two moth species defoliated as much as a third of the mountain birch trees that stretch across northern Norway, Sweden, and Finland. By 2014, some trees had recovered (top) while others had not (bottom). Photo: Jakob Iglhaut / Science News

By Hannah Hoag
11 April 2019

(Science News) – The Chugach people of southern Alaska’s Kenai Peninsula have picked berries for generations. Tart blueberries and sweet, raspberry-like salmonberries — an Alaska favorite — are baked into pies and boiled into jams. But in the summer of 2009, the bushes stayed brown and the berries never came.

For three more years, harvests failed. “It hit the communities very hard,” says Nathan Lojewski, the forestry manager for Chugachmiut, a nonprofit tribal consortium for seven villages in the Chugach region.

The berry bushes had been ravaged by caterpillars of geometrid moths — the Bruce spanworm (Operophtera bruceata) and the autumnal moth (Epirrita autumnata). The insects had laid their eggs in the fall, and as soon as the leaf buds began growing in the spring, the eggs hatched and the inchworms nibbled the stalks bare. 

Chugach elders had no traditional knowledge of an outbreak on this scale in the region, even though the insects were known in Alaska. “These berries were incredibly important. There would have been a story, something in the oral history,” Lojewski says. “As far as the tribe was concerned, this had not happened before.”

Top: Healthy crowberry shrubs grow among mountain cranberry in Abisko, Sweden, in September 2005. Bottom: A 2013 midwinter warming event near Tromsø, Norway, melted the snow. By May, these crowberry plants turned reddish brown from severe stress. When this happens, the leaves eventually turn brown, then wilt, turn gray and fall off. Photo: J. Bjerke and Hans Tømmervik / Science News
Top: Healthy crowberry shrubs grow among mountain cranberry in Abisko, Sweden, in September 2005. Bottom: A 2013 midwinter warming event near Tromsø, Norway, melted the snow. By May, these crowberry plants turned reddish brown from severe stress. When this happens, the leaves eventually turn brown, then wilt, turn gray and fall off.
Photo: J. Bjerke and Hans Tømmervik / Science News

At the peak of the multiyear outbreak, the caterpillars climbed from the berry bushes into trees. The pests munched through foliage from Port Graham, at the tip of the Kenai Peninsula, to Wasilla, north of Anchorage, about 300 kilometers away. In summer, thick brown-gray layers of denuded willows, alders and birches lined the mountainsides above stretches of Sitka spruce.

Two summers ago, almost a decade after the first infestation, the moths returned. “We got a few berries, but not as many as we used to,” says Chugach elder Ephim Moonin Sr., whose house in the village of Nanwalek is flanked by tall salmonberry bushes. “Last year, again, there were hardly any berries.”

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