1. ALASKA: A caterpillar spins a tale of changing climate (ClimateWire, 11/10/2008)

Lauren Morello, ClimateWire reporter

FAIRBANKS, Alaska -- Glenn Juday is in a hurry.

It's a chilly morning in early October, and the University of Alaska scientist is trying to outrun a snowstorm. He is headed just south of the city to the Bonanza Creek Experimental Forest, to plots of spruce, birch and aspen trees he's been studying for 31 years.

The project he's working on today began after the 1983 Rosie Creek Fire, which burned about 13 square miles south of Fairbanks, including nearly one-third of the trees at Bonanza Creek. But on this day, it's not the snow, but the effects of the summer's heat that have him worried the most.

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Juday initially hoped to document how the charred forest would rebound from the fire. But in the process, his detailed annual records of each tree's growth have started to tell a different story -- one about the ways climate change is reshaping the Alaskan interior.

As the state becomes warmer and drier, its trees are struggling to adapt. Across Alaska, average temperatures are 4 degrees Celsius warmer than they were a century ago, according to the U.S. EPA.

In Bonanza Creek, Juday has documented how those hotter temperatures stunt the growth of white spruce.

Eventually, the changing climate could alter the distribution of species, sending many trees north in search of cooler temperatures, according to recent reports by the federal Climate Change Science Program. By the end of the century, federal scientists predict, Arctic tundra could become Arctic forest. Boreal forest could transform into grasslands.

Some change is already evident. In southern Alaska's Kenai Mountains, for example, the tree line has risen an average of 1 meter per year since 2002, according to a report released last year by the Government Accountability Office.

In Alaska's interior, where Fairbanks is located, the birch and white and black spruce trees that form the bulk of the boreal forest are nearing the top end of their temperature range, pointing to an uncertain future.

Within 30 to 50 years, they could disappear from Bonanza Creek and forests like it, he says. "We face the prospect, in just a few decades, of experiencing temperatures that historically have pushed trees to the brink of survival," Juday explains.

Terry Chapin, a University of Alaska, Fairbanks, ecologist, is blunter: "It's really a question of whether there will be forests," he says.

Fires grow larger and insects march north

The shifting climate is altering the natural fire cycles that have historically helped shape the Alaskan landscape.

During the hot, dry summer of 2004, fires burned 6.6 million acres across the state, more than any year since 1950, according to the National Climatic Data Center. The next summer, another 5.5 million acres burned -- the third-highest total ever recorded in Alaska.

Glenn Juday. Photo courtesy of Glenn Juday.

Fires are starting earlier than they used to, scientists said, and they are larger. There are also more "fire busts" -- multiple, simultaneous fires.

Meanwhile, rising temperatures are also altering the balance between Alaska's trees and insects.

Take the spruce budworm, a forest pest whose young thrive on the green buds and fresh needles spruce trees sprout each spring. The little caterpillars once had a hard time gaining a toehold in Alaskan's northern tier of forests, thanks to bitter winter cold that killed off many young budworm larvae.

"We never used to have spruce budworm," Juday says, hiking up a steep hillside in the Bonanza Creek plot, carrying the professional-grade camera and tripod he uses to photograph his trees several times a year.

But that has changed over the last 20 years, since the first outbreak in Fairbanks occurred in 1989. Now, the budworm infestation is a regular occurrence.

The budworm's progress hinges on conditions in the late summer. "This is where temperature matters," Juday says. "The August temperature will tell the tale."

A warmer summer means more young budworms will mature to a larval stage that will allow them to survive the winter. "No amount of cold can kill it then," Juday says.

August temperatures in Fairbanks have risen over the last century by 3.5 degrees Celsius. Meanwhile, the start of spring has come earlier, giving the budworm young more time to grow before winter sets in.

Juday's research shows that the growing season in Fairbanks is now 50 percent longer than it was at the turn of the 20th century.

"Right now, we're experiencing probably the biggest change we've seen in this part of the world for hundreds of years," he says.

A crucial shift in balance between the pest and the host

Juday's white spruce trees aren't the only Alaskan forest-dwellers battling increased pest outbreaks.

Alaska's aspen trees are struggling with their own pest, the aspen leaf miner. The insect has thrived over the last four to six years, ending a period of at least a century during which there were no recorded heavy leaf miner outbreaks in the state's forests.

Shifting seasons, insect pests and changing fire patterns are remolding the Bonanza Creek forest south of Fairbanks. Photo by Lauren Morello.

Chapin, the UAF ecologist, points to the spruce bark beetle infestation that, since the 1990s, has claimed Sitka, white and Lutz spruce trees on 4 million acres in south-central Alaska, many on the Kenai Peninsula.

Research by the Alaskan Forest Service attributes the outbreak to warmer summers, which shorten the insects' life cycle. The beetle population explodes after two consecutive summers with average temperatures above 51 degrees Fahrenheit, the foresters found.

"All of a sudden, forests in southeast Alaska were decimated by bark beetles," Chapin explains. "They shifted from a two-year to a one-year life cycle. There was a shift in ecological balance between pest and host."

It's another sign that "if there's any place in the U.S. we have to think about adapting to changing conditions, it's here," he adds. Emissions cuts, he notes, are necessary but will likely not prevent some of the drastic changes forecast for Alaska, a state where temperatures have already risen twice the global average.

Sitting in his office on the UAF campus, Chapin is philosophical. When it comes to climate change, "Alaska is getting beyond its denial phase," he says. "The next thing is to think about new opportunities, new ways of doing things."

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