Drought may 'reset' forest ecosystems

By Don Thompson
The Associated Press

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An epidemic of bark beetles is killing millions of trees in areas from Alaska to Arizona. In the Southwest, an eight-year drought is killing many trees that the beetles don't.

"It's really a natural response in some ways, a self-thinning of forests," said Craig Allen, of the U.S. Geological Survey, in Los Alamos, N.M.

If the drought persists — and top scientists from across the West are betting it will — it may in effect "reset" many ecosystems, wiping them out and forcing natural succession to start over.

Scientists lamented that they can't predict when this drought will end or whether drier, hotter conditions are part of a long-term global warming.

Nor can they say what the forests of the future will look like.

"You're going from one concept to multiple unpredictable futures," said Ron Neilson, of the U.S. Forest Service Pacific Northwest Research Station in Corvallis, Ore. "The policy-makers are always coming at us with, 'What about the next 10 years, 20 years?' And that's the period about which we have the least knowledge."

The last sustained drought was in the 1950s, but it was nothing compared with this one because temperatures are markedly higher, the scientists said last week at a global-warming conference with a shrunken Lake Tahoe as a backdrop.

Higher temperatures have created such conditions that certain species of bark beetles have sped up their life cycle to produce a new generation every year instead of every two years, said Jesse Logan, of the Forest Service Rocky Mountain Research Station.

And nature's version of forest thinning creates its own problems: millions of dead trees like standing cordwood awaiting a match.

But once the needles drop off the conifers, researchers said they are less prone to the wind-driven treetop fires that have become prevalent in recent years.
 
President Bush's Healthy Forests Restoration Act authorizes up to $760 million a year to treat up to 20 million acres of federal forests and grasslands at risk of catastrophic fire.

Yet land managers are like generals who find themselves fighting the last war, said Julio Betancourt, of the Geological Survey's Desert Laboratory in Tucson, Ariz. "We ought to start thinking way ahead," he said.

The goal of last week's Mountain Climate Science Symposium was to identify and coordinate research that should be done in the next five years and then seek funds.

The group hopes to have a plan by fall.