Warmth boosts a beetle ruining Sweden’s spruce forests

By Ivar Ekman, International Herald Tribune
Vreta Kloster, Sweden (May 8, 2007)- For Goran Samuelsson, the proud owner of 70 hectares of majestic spruce trees here in southeastern Sweden, the forest is no place for fairy tales or fauns. It is his economic security- “a bank where you don’t have to bow to get what you need,” as he puts it. But recently, due to events that many scientists consider the result of global warming, Samuelsson has started seeing a part of his prized forest in a much darker light. He now calls it “hell.”


“It is sad,” he said as he stood among about 50 dead or dying trees, pointing out the clearing where he, while hunting for moose last November, saw the first three trees with red and dry tops. They proved to be the unmistakable signs of attacks by Samuelsson’s tiny new nemesis, the European spruce bark beetle.
“I’m not really worried about these,” he said, indicating the dead 70-year-old trees with their bark peeling, exposing the characteristic tree-shaped egg galleries of the insects. “I’m worried about what will happen if we fail to stop the beetles.”
Now some see nature, in the shape of the 5-millimeter hairy bark beetle, changing direction, steered by climate change. The beetle has caused havoc in Central Europe’s mountainous spruce forests for centuries, drilling through the spruces’ bark, where the insects lay their eggs, eventually killing the tree. It takes about 6,000 beetles to kill a 25-meter, or 80-foot, spruce.
Until now, the beetle has not been a big problem in Northern Europe, mainly because long and cold winters kept their numbers down. But for this year and the next, scientists are predicting an explosion in the number of beetles, a horde that could destroy 60 million cubic meters of trees — almost two-thirds of the yearly regeneration of Sweden’s forests.
“This is the worst situation we’ve ever seen here in Sweden,” said Bo Langstrom, a professor of entomology at the Swedish University of Agricultural Sciences. “Usually, the beetle only produces one brood per year here in Sweden. But last year, for the first time, it produced two.”
“If this continues, we will have much more serious damage than ever before,” he said. Climate change is a likely culprit, as manifested in the frequency and intensity of storms. The problems began when one of the biggest storms in modern times hit southern Sweden in January 2005, felling 75 million cubic meters of trees, mainly planted spruce. Some scientists say that the way that trees have been planted and harvested- on formerly open fields, and next to big clear-cuttings- have made them vulnerable to strong winds.
The felled trees provided the perfect breeding ground for the bark beetles, and when the storm was followed in 2006 by the longest and warmest summer on record, the beetles were given the chance to greatly increase their numbers. Then another big storm hit southern Sweden this January, and spring arrived early, letting the beetle start breeding quickly.
“Now we just have to pray for a cold and short summer,” said Mattias Sparf, a forest consultant with the Swedish Forest Agency. The same week in April when the Swedish beetles awoke from their winter slumber and began searching for fresh trees to breed in, the Intergovernmental Panel on Climate Change issued a report stating that increased insect outbreaks affecting forestry were “virtually certain.”
It remains to be seen whether countermeasures like poison traps and clearing of felled trees can contain the outbreak. But some voices are calling for changes in the forestry industry. Gustafsson, the ecologist and politician, says it is high time to plant mixed forests, with deciduous trees, such as oak and birch, mixed in with the evergreens. But for Samuelsson, the farmer whose forest has been stricken, business comes first: The price for spruce is higher than it has been in many decades, so despite his worries, spruce is what he plans to plant once the dead trees are cut down.
“Whichever way you look at it, there is such a thing called the market,” he said. “And the market rules.”
Related Resources:
Boston Globe
Forestry Center