[flohofwoe]

The bark beetle is not an invasive species in Central Europe though. The main reason is climate change (the last decade was increasingly hotter, drier and 'stormier') combined with a man-made tree mono culture (which goes back a few hundred years).

[leptons]

The same thing happened in California also due to climate change. The beetles here thrived far more than they used to due to shorter/warmer winters with less/no snow in the mountains, and beetle population exploded and they killed probably a million or more trees. Up in the mountains in California you can't drive anywhere without seeing thousands of dead trees all around you - and it's everywhere in the mountains here, probably millions of trees dead - I obviously don't know an exact count, but it's quite a lot.