Warming climate threatens Alaska's vast forests

KENAI NATIONAL WILDLIFE REFUGE, Alaska (Reuters) - Here in a 13,700-year-old peat bog, ecologist Ed Berg reaches into the moss and pulls out more evidence of the drastic changes afoot due to the Earth's warming climate.

Rooting through a handful of mossy duff, Berg, an ecologist for the U.S. Fish and Wildlife Service, shows remains of shrubs and other plants taking hold over the last 30 years in a patch of ground that has long been too soggy for woody plants to grow.

In other words, the ground is drying out, and the peat bog is turning into forest.

"There has been a big change," Berg said. Core samples taken from the bog show moss nearly 22 feet under the ground, with no sign of trees or shrubs growing here for centuries, Berg said.

In 50 years, the bog could be covered by black spruce trees, he said.

Welcome to Alaska, where the blow of climate change will fall harder than on any other U.S. state.

Records indicate that Alaska has already experienced the largest regional warming of any U.S. state -- an average 5 degrees Fahrenheit (3 degrees Celsius) since the 1960s and about 8 degrees Fahrenheit (4.5 degrees Celsius) in the interior of the state during winter months.

"We've got mounds of evidence that an extremely powerful and unprecedented climate-driven change is underway," said Glenn Juday, a forest ecologist at the University of Alaska in Fairbanks.

"It's not that this might happen, Juday said. "These changes are underway and there are more changes coming."

'BEETLES TAKE NO PRISONERS'

In a state that is one-third forest, the change will take the form of droughts, forest fires, and infestations of tree-killing insects like spruce beetles and spruce budworm moths.

Further north near the Arctic Circle, receding sea ice has major implications for polar bears, seals and dozens of species, as well as native humans who depend on the land to sustain them.

But here on the scenic Kenai Peninsula south of Anchorage, rising temperatures are partly to blame for an outbreak of bark-infesting beetles, which thrive in warmer climates.

Altogether more than 3 million acres (1.21 million hectares) of spruce have been killed in south-central Alaska since 1992, the biggest recorded outbreak in North American history.

"Beetles take no prisoners," Berg told reporters during a tour of the refuge. "It's a Mafia-style execution."

Today's beetle-infested forest is tomorrow's subdivision, and the beetle has set off a flurry of land speculation. "The realtors loved it," Berg said, describing how the new trend is to market clear-cut lands as "emerging view properties."

While wetlands like the ones Berg studies have acted as a speed bump for forest fires, the drying pattern has scientists worried about an uptick in forest fires.

Scattered at the outskirts of the bog are seedling black spruce trees, which burn more easily than white spruce and could provide a "fuel bridge" to allow fires to burn across peat bogs, which have long acted as a fire retardant.

Peat bogs are about 50 percent composed of carbon, and drying or burning would release heat-trapping carbon dioxide into the atmosphere.

(Reporting by Chris Baltimore, Editing by Sandra Maler)