Here in the Harz, especially in the National Park, we have quite some bark beetle troubles. There are just so many dead trees, because of the spruce monoculture left behind by the once sprawling mining industry in the area.
Back in the day, the miners needed loads of wood for their mining operations. They escpecially needed that wood to support all the mine shafts that were dug out in the area. Since they needed so much wood, reforestation became necessary in some areas where the natural mixed woods were replaced with fast growing spruce trees.
Since spruce isn’t native to the area it has no real defences against the bark beetles commonly found in the area. Once a single tree is infected, the trees around it are highly likely to get infected as well. And because all that is happening in a National Park were there aren’t many access roads it’s not easy to combat the beetle. Also, since it’s a National Park, you can’t just go around cutting down trees.
The best strategy against the bark beetle is to leave it no room to breed. It usually does that in standing dead or fallen trees and rests of harvestet trees. Once the beatles start breeding, they fly around to find other trees to lay their eggs on. The maggots than drill between the wood and the bark and damage the tree, often to it’s death. Off course nature is protected in the National Park, so you also can’t run around removing dead and fallen trees all the time, as such activities would disturb nature.
Now I come to the spruce monoculture in the Harz again: The longtearm goal of the National Park is it, to form the woods in the area to a more natural system by leaving them mostly to them selves, except were hiking paths or streets are involved. And the bark beetle is actually helping quite a bit, with nature taking care of the dead trees and new trees growing in between the dead the forest is on a good way to become more natural again, but it will definetly take a while for nature to do it’s thing.
So you’ll see quite a few dead trees in the Harz when you drive through the area in the next years. Just remember, it’s all for the greater good, which is a more natural forest in the high lying areas of the National Park. In the low lying areas, the bark beetle is actually beeing comabted to prevent it’s spread into economically used parts of the Harz.
Sources (most in German): https://www.landesforsten.de/nlf-spezial/borkenkaefer/ https://www.sueddeutsche.de/wissen/nationalpark-umwelt-oekologie-harz-borkenkaefer-wald-1.4486490 https://www.nationalpark-harz.de/de/aktuelles/2019/2019_04_23_Borkenkaefer/