The situation in Finland is still relatively better than in many other countries, but it has deteriorated.

“Now it begins. Never before have I seen such extensive areas of dead trees in Finnish commercial forests.” With this phrase, Samuli Junttila, a researcher at the University of Eastern Finland, commented on aerial photos showing bark beetle damage on the social network Twitter.

S. Junttila uses aerial forest photography to study the condition of large forest areas and stands from the air. “Usually, when studying tree health, it has been quite problematic to find study subjects because there have been very few dead or damaged trees. That no longer seems to be the case!”

Aerial photography also uses an infrared camera to identify dead trees from the air. Healthy, green vegetation strongly reflects infrared radiation, whereas dead vegetation does not.

What exactly is starting now, as S. Junttila wrote on Twitter? Beetles have appeared in Finnish forests in numbers Finland is not accustomed to. As is known, the pests attack spruces specifically.

“The reproduction of many pests is limited by temperature. In warmer weather, they are able to produce more offspring,” explains S. Junttila.

Meanwhile, drought reduces the spruces' ability to defend themselves against the bark beetle. Trees repel pests by secreting resin, but trees stressed by drought produce less resin.

“It was previously known that the bark beetle had been causing major problems in Central Europe for a long time, and a similar situation has been experienced in southern Sweden in recent years. It seems that now we are also beginning to see greater damage in Finland,” says a concerned S. Junttila.