What is Causing Trees to Die in Germany?
The one to blame might be a bit smaller than you would expect…
Last summer, I went on a backpack adventure with a good friend. After thorough research about how to avoid mosquitos and heat, we decided on Germany, and specifically, to walk the Harzer Hexenstieg (witches´ trail), about 100 km long. It would take us around 7 days to finish.
Some background
Located in Northern Germany, the Harz occupies around 2,000 square metres with its forests, lakes and rivers. The landscape is quite hilly, but we chose to take an alternative route around the highest peak´Brocken´. We thought it would be touristy and much overrated. As a result, we got pleasantly surprised by a beautiful wetland landscape with many swamp footbridges.
While we mainly chose the Harz area because of the forests and variety of landscape, we stumbled upon many bold trees between bushy neighbours, especially in this swamp area. Heaps of wood besides the paths did not escape our attention either, just like the process of many trees being taken down. Oncoming hikers told us this had to do with some sort of bug plague. I got curious and decided to do some research.
What (or who) is responsible?
Turns out, the one to blame is indeed a tiny bark beetle. This insect places their larvae in self-made holes in the bark, effecting mostly spruce trees. However, oak, beach and pine seem to suffer from their way of getting around as well.
Ips typographus (the European spruce bark beetle) has posed a problem since decades, but usually the trees are well-equipped for defense. Their sap and resin slow the insect down by making it harder to get under the bark.
Extreme drought and hot temperatures in the last years have made many more vulnerable. Saps are harder to form, and water stress leads to shorter roots (and thus troubles concering resouce acquisition). As opposed to that, the beetles seem to mainly benefit from hot temperatures. More of them survive the milder winters, and the insects emerge earlier in the year, making more generations possible. One is not so dangerous on itself; the power is in the number. Making all these holes, thousands of beetles at the same time can create loss of needles and can make the bark fall of, easily killing a tree.
What can be done?
The main solution offered is cutting down trees which are already too far gone and thus containing the spread of the bug. Foresters also experiment with using natural enemies of bark beetles, like wasps. They eat eggs and larvae of bark beetles, slowing down population growth. Reforestation with a variety of trees (as opposed to a monoculture) should lead to more resilient woods, preventing these plagues from thriving again in the near future.
However, many trees are affected and taking down trees as well as reforestation is very time-consuming and costly. Moreover, there is not so much question as there is offer for wood.
I know this is not really a satisfying end to the story. We will have to see how it plays out and hope for the best (and maybe for some harsh winters).
I can only say that luckily, there are still many trees left, at least in the Harz area. Besides listening to podcasts, hitchhiking in pouring rain, and swimming in ice cold lakes, my friend and I are left with the sweet smell and sight of spruces as one of our best memories of the journey.
More from me:
Story of a Passionate Biologist — Why am I on Medium?
5 Reasons Why Taking The Same Walk Never Ceases to Surprise
What I love about Terschelling — Exploring The Beauty of a Dutch Island
Thanks for reading! I hope you like my post. I am Mo Schouten, a Biology student located in the Netherlands. Capturing my environment with a camera is what I love most. — — Comments as well as tips are always welcome; leave them below!
