Forests can be some of the most pristine and intact terrestrial ecosystems in the world. The Amazon, Central African Tropics or Jungles of Indonesia are heavens for incredible biodiversity. And even in Europe there are old-growth natural forests like the UNESCO World Heritage “Ancient and Primeval Beech Forests of the Carpathians and Other Regions of Europe”. On the other hand, forests have been crucial to provide humans with some of our most important resources like construction wood, fire wood, (toilet) paper and energy. And in a future without fossil fuels but still rising population and energy demand, these resources will retain or even increase their importance as wood is the most important natural material to replace fossil fuels and plastic in many areas.
The climate crisis wreaks havoc around the world
In addition, forests are the most important carbon sink on land. But the overheating climate and extreme weathers cause massive damages in forests around the world. Australia, the United States, Canada and Siberia have experienced the biggest wildfires in decades or centuries. Central Europe has also experienced serious droughts in the last five years.
In Europe, most forests have at same point been completely chopped down because humans used too much wood. In the 18th century, foresters started to realize that this cannot continue like this. Wood is a renewable resource, but it renews very slowly. Unlike fields, you cannot just harvest forests every year. If you want big trees for building houses etc., it rather takes 80 years until they are ready for harvesting. Hence, this extreme weather comes upon forests that have been planted decades ago when climate change has either unknown or ignored and forests were designed solely to harvest wood.
The result in many Central European forests are gigantic clear patches in the forest. They are caused by bark beetles explosively spreading in spruce stands that were planted in locations that are not suitable for spruce and would normally host mixed deciduous forests. The drought has weakened the spruces, that naturally grow in cooler mountain or taiga areas. In these trees, the spruce bark beetles, a native pest specific to spruce trees, can reproduce easily as the trees are too weak to fend them off. The larvae start feeding on the wood and destroy the water and nutrient flow in the trees. Whole stands have died within a few years.
How should we respond?
This leaves forests and their managers in a situation, where they have to bring together many interests, ideas and threats. They are supposed to provide resources that humans need, habitats for wildlife and carbon sinks. At the same time, the climate crisis threatens their future, especially if they were planted without considering future climate changes. In this situation, the bark beetle outbreaks raise the question: What to do with the dead trees and the affected areas?
The two most extreme positions are taken by nature conservationists that campaign to leave these questions to themselves without intervening and by “old-school” foresters that want to replant the forests with fast-growing tree species to generate new wood as quickly as possible. We have worked on this topic previously in a nature conservation context and now we have met up with Tobias, a young forester, to exchange thoughts.
Prevention is key
The first thing that Tobias emphasized that many foresters takes this issue and nature conservation in general serious. For example, in his home state of Germany, Hessen, even before the large-scale bark beetle outbreaks of the last years, the state forestry service defined so called “Waldentwicklungsziele” (forest development goals). They define suitable tree species for each location that will still be resilient even if the average temperature rises up to 4°C and water will become scarcer. This is based on climate and hydrology models that predict conditions for each location in Hessen.
One of the nature conservation efforts by the state forestry service is their FSC certification. This brings a set of regulations about “environmentally appropriate, socially beneficial, and economically viable management”. Foresters must plant native tree species, keep a certain amount of dead wood and leave some forest patched for natural development.
This is also why the issue of the non-native or rather non-suitable spruce stands have been a topic long before the last years’ bark beetle outbreaks. Informed by the mentioned climate models, many foresters have known for decades that these stands are not resilient to climate change and something like this might happen sooner or later. Hence, they have started planting a diverse mix of native species in between the spruces. But trees grow slowly, especially when big trees around them use sunlight and nutrients before it can reach the younger ones. So, this is a very slow process that works rather on the scales of centuries than decades.
Disasters can be a chance
Consequently, the current bark beetle outbreaks are a crucial turning point for climate-resilient or future-proof forests in Central Europe. They are clearly visible proof that this spruce monocultures are ecologically suitable and economically viable only on specific locations and that these locations will become less due to climate change in the future. And this is not only visible to foresters or experts, but everyone in the forest, which increases public interest in this topic. It also forces foresters to make quick and fundamental decisions about the future of forests in affected areas.
These decisions must answer the question “What now?” meaning what should be done to the affected stands in terms of direct treatment and afforestation. Many nature conservationists advocate a non-intervention approach meaning that nothing should be done in the stands so that nature can develop completely by itself.
However, foresters are often not in favor of this approach. This has several reasons:
- It is easier for bark beetles to spread.
- Dead spruce trees that will fall at an unknown time pose a risk to bypassers and forestry workers.
- Trees falling in all directions makes the stand pretty much inaccessible. This means neither recreation nor forestry is possible here.
- In a pure spruce stand, it is much easier for spruces to regrow that for any other species. Accordingly, the tree composition would probably not change so much without any human intervention.
For these reasons, usually most infected spruces are cut down and removed from the forest as soon as possible. After that both approaches in different locations. They either let the forest regenerate naturally or they plant suitable species. The choice of tree species is always a compromise between the ecologically most suitable species and species that are economically profitable, i.e. produce wood in demand quickly.
Forests cannot do it all
And this compromise is often the problem that foresters face. When talking to Tobias, you clearly realize that he is a passionate nature lover and conservationist. So are many foresters. However, he clearly says that we cannot leave all forests to themselves because wood is a fundamental material for a green transition. If we want to use wood as a renewable resource, we must harvest forests just like we harvest fields. And this is not possible without managing forests and intervening in their development.
However, this does not automatically mean that these forests are ecologically poorer or have less biodiversity. There are many ways to create managed forests that are healthy, resilient and biodiverse. What often restricts ecological forestry are economic constraints. Tobias says that from a purely ecological point of view, it might make sense to plant slow-growing deciduous trees. But even if you follow ecological principles, you still have to create profit. This is often done by planting coniferous species like pine, larch, fir or douglas fir (rarely spruce nowadays) as they grow fast and straight meaning they produce perfect construction wood.
As so often, we cannot have it all. Commercial forests cannot provide massive amounts of wood, regenerate a financial profit and prioritize nature conservation all at once. Commercial forestry will always be a compromise between all of it. But fortunately, there is a clear shift in forestry from pure silviculture (as in agriculture, only with trees instead of crops) to a more holistic forest management, where nature conservation is a key component. Talking to Tobias proved once again that many foresters are important allies in nature conservation with an unrivaled knowledge about their local forests.