Time, complexity, resilience. These are the three key concepts on which the health and survival of any forest ecosystem is based. Three interrelated characteristics in a tight cause-and-effect chain: it takes a forest a long time to develop the complex fabric of interrelationships among its various organisms, and that fabric will be critical to ensuring its capacity for self-regeneration and its resilience in the face of natural disasters and climate change. But nature's slow pace collides with the frenetic rhythm of productive exploitation, which imposes simplified structures on forests in the name of efficiency, and in defiance of resilience.

Finding a balance is increasingly urgent, as countless ecosystem services depend on forests, starting with biodiversity protection and climate mitigation. We talked about this with Miroslav Svoboda, head of the Department of Forest Ecology at the Czech University of Life Sciences (CZU) in Prague, a scholar of natural regeneration mechanisms and an expert in dendrochronology, the discipline that studies tree timelines.

ph Roland Gockel


A forest is more than just a collection of trees,” said Suzanne Simard in a famous TED Talk. What is your definition of a forest?
A forest is a complex system composed of a wide range of different species living together in one place. It is certainly not just trees: it ranges from soil microorganisms to fungi, from plant species to animals. Foresters actually tend to view it merely as a collection of trees, but the management of a forest cannot fail to consider the impacts on the whole system and the interrelationship between the various organisms.

How important is the concept of symbiosis in this definition?
This is a fundamental mechanism in the life of a forest. Some species cooperate with each other, and recent studies have shown that trees in particular form symbiotic relationships with soil organisms: an exchange that benefits both.
However, one should not make the mistake of idealizing forests as peaceful environments in which all species cooperate with one another. There is, in fact, much competition for survival: these are places where each individual fights for its living space and for the resources it needs. And the result of this competition is that sometimes some species succumb.

In recent years, there has been a growing interest – both in scientific research and in the public imagination – in what we might call “non-human, non-animal intelligence” (think of Simard's or Wohlleben's best-selling books on trees, and Sheldrake's or Stamets' on fungi). How would you describe the intelligence of trees?
I would be very cautious in talking about “intelligence” as we understand it from the human perspective, because once again we risk idealizing the issue. However, there are more and more studies and research going in this direction that are showing how indeed trees are capable of reacting in many different ways to a variety of events. So certainly, it can be said that they are intelligent in the way they adapt to changes in their environment. After all, trees have lived on Earth for hundreds of millions of years and have evolved to survive changes in the Earth's climate, learning to adapt even to extreme and incredibly harsh conditions for life. This is what I like to call their “intelligence.”

This adaptive capacity is ultimately at the heart of forest ecology, i.e. the discipline you are concerned with. What factors impact the balance of forest ecosystems the most today?
Today, climate change is generally cited as having the greatest impact on forest ecosystems worldwide, and its effects are indeed very serious. However, it must be recognized that the worst consequences on the global state of forests come from direct human activities. For example, in Europe, we have practically turned most of our forests into “managed forests,” thus determining their future composition and appearance. And this goes to interact with climate effects.

I take a specific example. In the Czech Republic, we have had in the last three years a major problem of bark beetle infestation, which has attacked coniferous forests used for timber. The spread of this pest is linked to the drought, and of course, everyone has talked only about the harms of climate change. However, we should not forget the responsibilities of foresters, who have transformed the country's forests, generally composed of spruce, oak, beech, and other tree species, into forests dominated by conifers. We have basically created the conditions for the perfect storm, making ecosystems much more vulnerable to both weather conditions and pest attacks.
Similar situations are occurring all over the world. We transform forests obeying only a vision of productivity. We create “simplified” forests with few tree species (those best for wood) and less intricate structures. But in this way, ecosystems become less resilient to climate change and less resistant to events such as drought, fire, or insect and pest infestations.

It is paradoxical when you consider how much we talk about regenerating ecosystems today. Instead, we only weaken the natural regenerative and “self-healing” power of forests. What should we do then to help them be more resilient?
As we said, trees have been on Earth for millions of years and have evolved to adapt to the climate. The problem is that the current climate change is unprecedented in the speed with which it is happening: in some regions, changes in rainfall patterns and temperatures are so sudden that trees cannot cope. Along with climate, the way forests have been managed in the past has also created an unprecedented situation.

In nature reserves in Central Europe, however, we can observe the great natural self-healing power of forests. When they are not modified by humans, they manage to recover and regenerate rather easily even after a bark beetle infestation, a fire, or a storm. And, indeed, the new layer of trees that regrows after a natural disaster is often richer in biodiversity and more structurally diverse than the previous one, which also makes it more resilient and durable. But it takes time. And certainly, this new forest, from the perspective of timber production, will not be as efficient as foresters would like. This is mainly the reason entire forests have been replanted in the past: to have the most productive species, an easier structure to manage, and above all to get the wood as fast as possible. Now we are finally beginning to understand that giving forests time to self-regenerate is good both for biodiversity and for their future resilience.

However, there are cases where natural disasters or climatic conditions are so severe that they impair the self-regenerating capacity of forests, damaging not only wood production but all other ecosystem services. In such cases, there is talk of “helping” forests to regenerate: that is, if native species are not resilient enough, there are plans to introduce more resilient species. There is a lot of debate about these kinds of practices, however, and I would be very cautious about using them, as we have had bad experiences in the past. Introducing non-native species into an ecosystem is always a risk. And even though occasionally it may seem like a good idea, and it is done with the best of intentions, it can turn into a nightmare.

In short, best not to interfere too much.
Correct. One might think of using these techniques only for forests cultivated for productive purposes, but they must always be offset with areas where nature is allowed to work at its own pace. Diversification of forest management is therefore, in my opinion, the way forward.
However, a balance must also be found from a geopolitical point of view. Otherwise, what happens is that, for example, we Europeans, in order to preserve our forests, go and exploit the forest resources of other countries, destroying their environment. It is a very complex situation, but I personally believe that we should apply more the principle of “think globally, act locally.”

ph Giada Connestari


You mentioned the ecosystem services provided by forests. Besides wood and, of course, oxygen, what are the others?
There is the regulation of the water cycle and microclimate, the protection of the soil and its fertility. There are “non-material” services, such as the well-being that a walk in the forest gives us, the relief from stress. There is biodiversity protection, since forests are the habitat for so many species. And of course, there is climate mitigation, given forests act globally as carbon sinks, storing CO2 in their biomass.
It's a very broad and complex range of functions, and that's why it's very difficult to manage forests and why we need to have several nature reserves and protected areas to ensure the continuity of their ecosystem services.
Of course, we will continue to need timber, but we must realize that it is not an unlimited resource, and we cannot push its consumption relentlessly. We should be more careful about our uses of it and start thinking of wood as a resource that also has negative environmental impacts, both in cultivation and production, and that is not carbon neutral.

This is actually a point that tends to be missed: the dominant narrative emphasizes only the sustainability aspects of wood.
Precisely. Wood is generally presented as a carbon neutral resource, but it is not, or at least not for certain uses. Ideally, it should be used to manufacture durable goods, not for disposable or otherwise short-lived products. Burning it for energy purposes should be the last option, reserved moreover only for waste wood. Unfortunately, however, this is not what happens today. In some countries, even in Europe, people are importing timber, cutting trees, and planting forests just to burn their biomass, even receiving subsidies for this purpose. This is hardly a use that can be called climate smart, especially when the wood is transported from one part of the world to another.

Speaking of carbon neutrality, from the perspective of CO2 storage, is an old-growth forest or a young one, perhaps replanted after a cut, more effective?
This is a very complex issue, on which there are a great many studies. But what is often forgotten in these debates is the timescale.
As humans, we still have 20 or 30 years to radically change our consumption and production system and become carbon neutral. But if we cut down a forest, we create a carbon debt that can only be repaid in 100 years, or even 150 or 200 if it is a tropical forest, with 500-year-old trees. And even if we replant the forest and let it grow, it would still be too late to offset the CO2 we are emitting now.
In short, cutting down a forest may indeed have a carbon-neutral balance, but only in the long run. In the short run, on the other hand, if we preserve the most mature forests, they will not only produce no emissions, but will continue to grow by storing carbon for years to come.

Speaking of timescale, one of the branches of your research has to do precisely with tree time: dendrochronology. What is it all about?
Trees, as we know, grow by forming rings. This is especially typical of the temperate zone, where growth stops in winter, thus creating this visible alternation in the trunk section: in practice, each ring corresponds to a year.
The rings thus function as a kind of memory, containing information about the environmental conditions in which the tree was at a given time: temperature, climate, and possible competitive conditions in the surrounding environment. All of this can be analyzed and measured. There are several methods for reconstructing, from the rings, what was happening in the past around the tree, from the amount of rain to natural disasters. It is fascinating and can help us not only to understand the past, but also to have a deeper understanding of the present situation and in a sense to predict the future and implement more effective management strategies.

Preserving ancient forests therefore also means preserving an important historical memory.
Absolutely, forests are a cultural heritage, and it is our responsibility to protect them for that reason as well. Otherwise, our children and grandchildren will hold us accountable in the future.

Download and read issue #47 of Renewable Matter on Trees


Image: the Arvière Forest in the French Alps (ph Giada Connestari)