Climate-stressed woodlands in Germany are under attack from bark beetles. 

"The insect eats the bark and lays eggs inside, the larvae then start to eat the trunk and block the nutrient pathways of the tree, which dies in about four weeks" says forest ranger Arne Barkhausen. 

Due to increasingly warmer global temperatures, vast areas of forests have become tinder-dry dead zones. 

Peter Biedermann of Würzburg University's Department of Animal Ecology and Tropical Biology says "since 2018 the attacked trees have been under water stress and their roots are no longer deep enough,".  

Drought-stressed trees also become too weakened to produce sufficient amounts of the sticky sap that repels bugs, such as bark beetles, because of its naturally produced insecticidal compounds. 

Derk Elhert, head of wildlife in the city-state of Berlin, says there are few effective ways of fighting back against this problem. 

"We have trouble coping with it, we can't use chemicals, when the animal is already in the tree, it stays there, we therefore try to support the natural enemies of bark beetles, especially wasps, which like to eat their eggs and larvae." 

Warmer winters mean greater numbers of beetles survive each year as more of them are able to survive and emerge earlier in the year. 

The bark beetles that inhabit these German forests are not breeding just once or twice, but are producing up to four generations per year. 

Biedermann says Germany's forestry monoculture, where thousands of trees are planted in neat rows, is making the country's trees vulnerable. 

The Forest Owners' Association also supports greater ecological diversification of forests, supporting the idea that Germany needs to transition towards planting trees which are better adapted to global warming, such as the American red oak or the Japanese larch.  

But the association says for this to be done effectively, the predicted cost of the move could be up to $2.5 billion.