These small, brown-colored insects prey on Picea abies, one of the most common tree species in Finland, and slowly destroy entire woods.

Pieces of their bark peel off, twigs fall from dead branches: digging to lay their eggs, the beetles devour absolutely everything around conifers and end up killing them by preventing water and nutrients from the soil from reaching the branches in height.

"These insects have wreaked havoc across central and eastern Europe, especially from 2018," Markus Melin, a scientist at Finland's Institute of Natural Resources, told AFP.

The risk of seeing this epidemic spread is "much higher now" because of global warming, he argues.

"We have to accept it and adapt. Things change very quickly."

Conifer killer beetles near Vikajarvi in ​​Finland on July 21, 2020, image courtesy of the Natural Resources Institute of Finland © IpsGallery_MarkusMelin / NATURAL RESOURCES INSTITUTE FINLAND/LUONNONVARAKESKUS/AFP

The threat is usually far greater in southern Finland, but the scorching summer of 2021 has seen bark beetles wreaking havoc "far north", in the Kainuu region.

"An ugly cycle"

"It's a well-known phenomenon: conifer bark beetles are one of the species that benefit the most from global warming to spread," says Markus Melin.

These beetles choose trees already weakened by hot summers and lacking water, while increasingly warm winters and the absence of frozen ground make it difficult to protect trees from storms.

A conifer attacked by bark beetles near Vikajarvi in ​​Finland on July 19, 2021, image courtesy of the Natural Resources Institute of Finland © IpsGallery_MarkusMelin / NATURAL RESOURCES INSTITUTE FINLAND/LUONNONVARAKESKUS/AFP

The increasingly warm climate also accelerates the life cycle of bark beetles.

"Their mortality rate drops and they reproduce much faster," laments Markus Melin.

If they first choose the weakest trees, once they have become very numerous, the bark beetles attack the healthy trees.

If the rangers do not react in time by removing the weakest trees, "suddenly the bark beetles, which have become very numerous, are able to attack the healthy trees", explains Markus Melin, " accelerating the cycle of destruction".

© 2022 AFP