Deep in the Finnish forests, moss and blueberry bushes hide a deadly threat to the boreal forest, which is as important to the planet as the Amazon rainforest.
With parts of the bark peeling off and needles falling from dying branches, more and more trees are being killed by the spruce bark beetle, which is moving further north as the climate changes, reports an article on Phys.org (AFP).
The small brown insects attack spruce (Picea abies), one of Finland's most common tree species, and can cause enormous damage to forests.
The spruce bark beetle burrows through the bark to lay its eggs, feeding around the spruce and killing it by preventing water and nutrients from reaching the higher branches.
"The species has caused enormous damage throughout Central and Eastern Europe, especially since 2018," says Markus Melin, researcher at the Natural Resources Institute Finland, to AFP.
With climate change, the risk of the spruce bark beetle spreading is "much greater now", Mr Melin adds.
"We have to accept it and adapt to it. Things are changing fast up here."
The threat is greatest in southern Finland, but during the warm summer of 2021, bark beetle damage was "unusually high in the north" in Kainuu in northern Finland.
Nasty loop
The beetles thrive in weakened trees. Warm summers mean there are more water-thirsty spruces, while warm winters mean there is no frozen ground to protect the trees from storms.
Warm weather also speeds up the life cycle of the spruce bark beetle, which means it can reproduce faster.
"Extremely hot summers favour the bark beetle significantly. They have less mortality and reproduction is faster," says Melin.
While beetles normally target weak trees, when their numbers reach a tipping point, they can start attacking healthy trees.
"It's a nasty loop," says Melin.
If foresters do not react in time by removing weakened spruce trees, "suddenly there are so many beetles that they can attack healthy trees", further accelerating the cycle of destruction, Melin said.
