AAS, Norway A spruce tree has smothered a few beetles by oozing resin from its trunk, repelling an attack by bugs that seem to be advancing northwards with climate change in a threat to forests and timber companies.
Other sickly spruce trees scarred by bark beetles have been less successful in the snow-covered forest near Oslo, where scientists are seeking ways to halt insects whose relatives have caused millions of dollars in damage in North America.
"The effects of climate change are likely only to be positive for spruce bark beetles," said Paal Krokene, a researcher at the Norwegian Forest and Landscape Institute inspecting a Norway spruce forest in Aas.
"They don't have that many predators, and they don't face that much disease," he said in a forest where scientists last year hung up small plastic bags on trees containing a scent emitted by male beetles to attract females to test the trees' resilience to attacks.
The research is an effort to seek benefits from global warming, which is likely to help boreal, or northern, forests grow better and advance north, producing more timber to meet rising demand from China and other emerging economies.
But some pests may fare better in a warming climate than the trees -- partly because they grow and can adapt faster. That is also a threat to earnings by forestry firms, which are backing research and trying to adapt forestry management.
Milder, muddier winters could also bog down heavy machines used by timber-related firms like International Paper (IP.N), Abitibi ABH.TO, Stora Enso (STERV.HE) and SCA (SCAb.ST). More powerful storms would present challenges, as would fire sparked by lightning where conditions turn drier.
In one of the worst northern insect attacks, more than 16 million hectares (39.54 million acres) of pine forest in British Columbia have been killed in a decade long-infestation by mountain pine beetles, which has now entered Alberta.
The U.S. states of Colorado and Wyoming also are badly hit.
Jim Bouldin, an ecologist at the University of California Davis, said there was strong evidence that the beetles had moved northwards and to higher elevations in Canada and the United States to forests that had been free of attacks for many hundreds of years.
The British Columbia government has stressed that climate change is a big factor in the beetle spread, mainly on old lodgepole pines, helping make the case for a comprehensive carbon tax -- the only one in North America so far.
But pests are not always destined to win in boreal forests in a ring from Russia, Europe and North America. "Prediction in ecology is difficult enough to begin with," Bouldin said. "Climate change makes the problem that much worse."
Thinning of forests, fire breaks and other measures can help cut infestations. Tougher trade rules can avoid the import of pests on infected wood. And Nordic nations say that their forests, harvested more regularly, seem less vulnerable.
"Scandinavian forests are not subject to such risks as in Canada since they are more managed. You do not have large tracts of elderly, virgin forests that are vulnerable to attacks," Bjorn Lyngfelt of SCA Forest Products said.
And the U.N.'s Food and Agriculture Organization (FAO) said in a 2010 study that it noted "no significant trend" in global insect and disease outbreaks in the world's forests from 1990 to 2005. But that may be partly down to a lack of data.
Attacks by the larch bud moth in Switzerland have apparently stopped over the past three decades, the FAO said.
Cold snaps this winter in parts of the Northern hemisphere may have killed some insects even though 2010 was tied as the warmest year on record with 2005 and 1998.
In Europe, about 20 nations have reported damage from the spruce bark beetle, some in new areas further north and making it the most widely reported pest, according to the FAO. Others include the gypsy moth or the European oak leaf roller.
At Aas, a few large trees have repulsed beetles by oozing sticky resin, a defence evolved over millions of years. The resin on one tree has entombed beetles less than 0.5 centimetre (0.2 inches) long that attacked in 2010.
Other trees have been deliberately infected with a fungus carried by the beetles. The research will add to a study in Canada showing that the fungus carried by mountain pine beetles weakens trees and can even feed on their defensive resin.
Forestry companies are investing in research and new technology, for instance lighter harvesting machines that will not get bogged down in muddier conditions.
Lyngfelt said SCA was using new tyres that allow a driver to let out pressure from the cabin to spread weight if hard ice tracks melt. SCA is Europe's largest private forest owner.
Terhi Koipijarvi of Stora Enso in Helsinki said it was impossible to know if a recent combination of chill winters and warm summers in the Nordic region might help by promoting tree growth while killing off pests in winters.
"Although cold winters do make wood transportation easier, warm summers do not automatically mean better growth, as growth is dependent on so many other factors -- humidity, nutrients, insects, etc.," she said.
And some pests live beneath snow in winter, which can act as an insulating blanket. Summer temperatures may be more critical -- bark beetles can sometimes produce two generations rather than one, meaning two waves of attacks on trees a year.
Moderate climate change is likely to promote tree growth and mean more timber, according to a report from the U.N. panel of climate experts. "Consumers will experience net benefits, while producers experience net losses," it said in a 2007 report.
But it added "fire, insects and extreme events are not well modelled".
(With extra reporting by Allan Dowd in Vancouver; editing by Michael Roddy)
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