“Every day we receive more information through our mapping service,” Risto Kalliola, a geography professor at the University of Turku, told AFP.

He described the phenomenon as a “local mass extinction of pine forests.”

The areas most affected are rocky coastal areas with infertile soil that is easily exposed to drought, he said.

A few years ago, groups of dead, brown pine trees suddenly appeared on the southern coast of Finland. Researchers are now trying to find out the cause of this phenomenon.

“Something is happening in our nature and we have to take it seriously,” said Kalliola.

Similar pine diebacks have occurred in other northern European countries, including neighboring Sweden.

“What is new in Finland is that this phenomenon has only recently become widespread,” he said.

He believes that various factors such as insect infestations and fungal diseases could be the cause of the local mass extinction – all exacerbated by global warming.

“During warm summers with heat waves and weeks of rain, trees in vulnerable locations suffer and their ability to defend themselves against pathogens decreases,” he said.

Kalliola said the exceptionally warm summer in Finland this year had caused stress to the trees.

“The less water in the soil the trees can absorb with their roots, the less they can survive heat waves and droughts,” he said.