Image: Forest in the German Harz Mountains that has been damaged by the bark beetle.
At the moment the news talk a lot about of the wildfires in the Amazon and the Arctic. But climate change and human activity also pose other dangers to forests, as can be seen in Germany.
During this summer family and friends had told me quite a bit about the extreme heat wave and drought in Germany. I had also heard through the news that German forests were suffering as a consequence.
However, none of this prepared me for what I saw when visiting my family home in the Harz Mountains in the middle of Germany.
As long as I can remember, the area around my home town has been covered in dense spruce forests. Much of my childhood was spent roaming these forests, looking for interesting animals and playing with friends.
When we approached my home by car at the end of August it was very clear, that this vast coniferous forest is sick. Like in the image above, many trees had lost their needles and large proportions of the forest had been felled leaving empty, moon-like landscapes.
You might think that the trees are only dying because they do not get enough water, but it is not as simple as that. Yes, the drought and hot temperatures limit the trees water supply. Nevertheless, the coniferous trees are still able to get enough water for their basic functions like photosynthesis. But the lack of water damages the spruce’s ability to defend against pests like the bark beetle.
The bark beetle is a tiny insect measuring about 6 mm (0.25 inch) that reproduces inside tree bark. The male and female drill into a tree to build a chamber for their eggs. After hatching the larvae bore away from the egg chamber feeding on the inner bark. This harms the part of the wood which transports water and food. In addition, the plant’s ability to form fresh bark is decreased. As a consequence, the tree will slowly die.
Like our skin the bark of a tree keeps out diseases and parasites. The normal response to a bark beetle attack is the secretion of tree sap to suffocate the beetles and their larvae. But in the event of extreme drought and heat, the trees cannot produce enough sap. Like the human immune system, the tree’s defenses do not work well under extreme stress.
The bark beetle has always been a pest in the Harz Mountains, my home area. One reason for this is that the trees are grown as a monoculture that mainly includes spruce. Deciduous trees are much more resilient towards the bark beetle and can form a natural barrier when planted in between spruces. Unfortunately, the forest is cultivated and managed by the timber industry which is only interested in the fast-growing spruce.
Despite the old monoculture problem, the current explosion of beetle infections is unprecedented and a consequence of climate change. Summers have continuously gotten hotter. During this year’s July heatwave even the – normally chillier – Harz Mountains reported temperatures above 35 degrees Celsius over several days and many new temperature records. At the same time the amount of rainfall in summer has decreased. Also, warmer temperatures allow more bark beetles to survive the winters.
The sad part of this story is that the National Park in the Harz Mountains is most severely affected. The park was founded in the early 1990s on former timber industry lands, covered with spruce monocultures. The aim was to let the land develop naturally into a mixed forest over many years. Now climate change and the bark beetle seem to be speeding up this process by destroying most of the spruce trees.
While the timber industry removes damaged wood to prevent healthy trees from getting infected, this cannot be done in a National Park where nature must be left to its own devices. As a result, the areas containing sick and dead trees are much larger in the National Park compared to the timber forests. This development could be a chance for deciduous trees to colonize the National Park faster forming a natural, mixed forest.
The future of the timber industry forest is not as clear. It is obvious that spruce monocultures will not survive the changes that global warming brings for much longer. There are now discussions in Germany to introduce foreign tree species that can cope better with heat and drought to replace the spruce. Maybe some forestry commissions will even move towards more natural mixed forests.
Looking at the dead trees and moon-like landscapes right now, I am wondering if this area will ever regain its former beauty. I cannot help but ask if my own children will ever see the vast forests of my own youth here. You do not need wildfires to destroy large amounts of forest. The trees in Germany are being destroyed by climate change and a tiny beetle.
I believe that the Harz Mountains and other German forests will eventually recover, the National Park by slowly developing into a natural, mixed forest and the timber forests possibly by introducing foreign tree species. But there is a chance that the spruce trees, that have been so iconic for German forests over centuries, could be gone.
A tang of science 