Humans could avoid the worst impacts of climate change if we just take a step back and stop meddling with forests, according to German forest scientist Peter Wohlleben.
In 2015, the publication of Wohlleben’s The Hidden Life of Trees: What They Feel, How They Communicate —Discoveries from A Secret World changed how the world thought about forests.
Now Wohlleben is back, with The Power of Trees: How Ancient Forests Can Save Us if We Let Them, to explain how forests are humanity’s greatest hope when it comes to adapting to a rapidly warming world.
Wohlleben will be in conversation with Arno Kopecky in a Tyee-sponsored event at the West Point Grey United Church at 7 p.m. on Sunday.
The Power of Trees comes with some pretty cool good news messages. Forests have been growing for 300 million years and have successfully survived changing climates before. They know how to keep themselves cool during heat waves and how to hold on to water during droughts, and are able to pull water inland to support plant growth thousands of kilometres from the sea.
Unfortunately, however, humans tend to think we’re smarter than a forest, Wohlleben says, often with disastrous consequences.
Some of Wohlleben’s lessons also run counter to current conventional wisdom about best practices for forest stewardship — including his assertion that it’s not actually the best idea to replant a cutblock after it has been logged.
Replanting an area after logging is harmful for the new trees and for the millions of microbes and fungal life forms that live in the soil, he says.
Trees pass lessons on through their DNA, Wohllebehn says, so a tree that grows in its parent's shade will know to be cautious of putting green shoots out in the early spring if the area is prone to late-spring cold snaps, for example. Replanting an area with seeds grown in a nursery means the young trees are foreigners, setting out in life without a local guidebook and with limited ability to communicate with the forest around them.
Replanting an area is also damaging to the millions of bacterial and fungal lifeforms in the soil, Wohlleben says, because it acts as a “wholesale removal of everything they rely on to survive.” Imagine if humans around the world tore out our crops of corn, wheat, oats, barley and rice, which all belong to the sweetgrass family, and replaced the crops with other grasses like ryegrass and meadow fescue, he says. There’d be global starvation — cereals make up 50 per cent of our global diets. It's no different when we replant trees, he says.
Another example Wohlleben points to is local German deer that eat up plump young saplings that get planted after an area is logged. To protect the saplings Germany doubled how many deer hunters were allowed to shoot. But this has led to deer being frightened of clearcuts — so instead of venturing into logged areas and eating grass that grows there deer are eating new shoots, twigs and bark from small trees in forested areas, which damages the forest.
To get a better idea of how trees can help humans adapt to climate change and what lessons B.C. can take from his new book, The Tyee spoke with Wohlleben from his home in Germany, where he manages a beech forest for the municipality of Hümmel. The following interview has been edited for length and clarity.
The Tyee: What do you mean when you say we need to get out the way of forests to let them heal?
Peter Wohlleben: Forests have been around for 300 million years. When we talk about rebuilding forests and making them resilient, as we do here in Germany, some people think they can do a better job than the trees. We do not have a single example of an artificial forest being more resilient or better at anything than a natural forest. Forests act like a whole organism: it's not just about trees. It's the bacteria, fungi, insects and so on. They all work together to stabilize forest ecosystems. We've been able to document about 10 per cent of the all the species that live in a forest. To build a forest you have to know how every single species combine correctly. We're not able to do so, so we should leave it up to the trees to heal the forest.
What about Indigenous peoples? Here in B.C. people have been living in and managing forests for thousands of years.
I know a little about how on the coast of B.C. there were what was thought to be native forests which turned out to be forests managed by Indigenous people. They were so rich in biodiversity. That’s a good example actually — First Nations didn’t have a university course on forestry, they knew how to care for them intuitively because they regard trees as living beings with needs. People also have needs. The question is how you balance the two. It's much better to go with your gut feeling than to think you've researched everything — which is impossible — but some people think they can alight the last secrets of nature and improve the forest.
It's very good to learn from Indigenous people because environmentalists now know that the most intact forests are best managed and best protected by Indigenous people living in those forests.
I live in B.C. which has a massive logging industry. Analysts are warning that the industry has over-logged and we're watching its collapse. Jobs are getting scarcer which is already having a huge impact on communities. Does letting forests heal have any short-term benefits that could help these communities?
We’re having the same discussion here in Germany because we have the same forest management system. The discussion is always about jobs and raw material. The use of timber is OK: the important question is how much and how we do it. It’s not my opinion to save every forest and push all people and chainsaws out.
In B.C. there’s more primeval forests than in Germany, where we have not a single square metre left. We’ve been logging a lot longer and more efficiently, but in a bad way. We see this all over the northern hemisphere, the breakdown and dying of forests. Bark beetles and climate change get blamed. But the most important factor that's not discussed is forestry, which weakens the forest.
What I’ve seen of B.C. reminds me of the Black Forest in Germany, which was once a virgin forest of beech and oak. Now it's a plantation of conifers just like in B.C. I remember driving down a logging road in B.C. 70 kilometres away from anything and I said “now I understand the news that we get in Germany about the bark beetle infestations.”
Which takes us back to another forest function. What is more important to people: water or timber?
Look at hot summers like the tragic case of Lytton where it nearly hit 50 degrees C. Germany is around the same latitude and our highest summer temperatures were 40 degrees C but those temperatures could happen here too. Forests can pull down summer temperatures by 10 to 15 degrees on average. We understood this 200 years ago but forgot and now we only think about timber. But to harvest timber you first need a forest.
The hotter it gets the more biomass a forest needs for itself.
In the Middle Ages doctors thought bleeding patients was good for their health. Now we know this weakens people. It doesn’t make them more resilient. It's the same for forests when it comes to climate change. Forests need more biomass to make sure the water cycles remain intact. Then we have to look at how much timber we can harvest without losing any forest functions. You can measure the temperature and health of a forest very easily by satellite. We should do this. And after every harvest we should check again and ask if we can go on or if we have to reduce the timber harvest.
You say plantation forests are more susceptible to disease, flooding, fires and landslides. That sounds like a recap of B.C. in 2021. Have you just been watching news broadcasts from B.C. while writing this book?
Hah! No, we’re really seeing this all over the world, especially in the northern hemisphere. In Germany people have been very arrogant. They say “we're not concerned by wildfires, we always have enough water.” Then in the last five years we experienced all bad things, so we are aware now that we’re in a hotspot for climate change and thinking about what we need to change.
We’ve had around 1.8 degrees C of warming, it's very bad. We’re all being impacted by the same climate change and practice the same system of forestry. A primeval forest has moss and lichen and acts like a water pouch. Then they’re logged and planted and become second or even third-growth forests and they get drier and drier. The bark beetles are the last nail in the coffin. They’re pointed to as the reason forests are dying but they’re just taking the chance they’ve been given.
You talk about how conifers like spruce drink shallow rainwater that falls year-round. What could climate change mean for B.C.’s trees, which are almost exclusively coniferous thanks to forestry practices that replant pine and fir and prevent other trees, like aspen, from growing?
It’s a bad idea to spray herbicides to reduce broadleaf trees. Aspen are very good at growing in hot, dry summers. In Germany we never had wildfires because the only coniferous trees grew high in the mountains. Now we have conifer plantations that burn very easily. Aspen are some of the first trees to grow back — we don’t yet know how they get water in these hot, dry summers — but they grow very fast and create a humid climate for the next generations of trees to grow in.
Aspen also cool wildfires when they burn. They’re not dangerous to a forest.
Just outside of my window I’m looking at Douglas fir. They were planted because it was thought it would grow and make a wonderful timber industry. But they’re dying and we don’t know why. For me it’s a good reminder that we don’t know very much about what is going on.
What we do know is that big intact forests — not a single tree — can stabilize the climate and even locally reverse climate change. If you re-establish a forest by 10 per cent in a landscape you cool the local climate by one degree C on average.
We are not letting trees migrate to try and adapt to climate change. We block them with cities and roads; control what trees grow in plantations and cut down unwanted young trees. How can we change this?
In Germany the forest industry created a new word, “assisted migration.” The problem is we can’t ask trees if they’d like to migrate so assisting in a migration that isn’t asked for is a problem. We don’t know how far they’d like to be moved north — and then what about the ecosystems already in the north? Are we replacing them? What about the organisms living there?
There’s a tree that grows here in Germany and the same tree also grows near the Mediterranean Sea, where it’s used to higher temperatures. Scientists took southern seeds and planted them in the Black Forest. It was the exact same tree species but it didn’t grow well. They did molecular genetic research and found the local fungi in the Black Forest didn’t like the trees from the south. So humans say “this is the same tree species” but the fungi says “no, it’s not and I won’t co-operate with it.” We need to remember it’s a human definition to identify something as the same species. Highly specialized fungi and insects, for example, may disagree.
This shows how little we know about forests. We can estimate that in a forest 90 per cent of bacterial species and 90 per cent of fungi species and thousands of insect species are unknown to scientists. In one handful of porous soil, Norwegian scientists found 40,000 different bacterial species and 50 billion bacteria. If we’re exposed to one wrong bacteria we will die, and if don’t have one right one we will also die.
Another example is ash dieback disease which is found in the northern hemisphere. Only a certain percentage of trees survive and no one knows why. Research from this past summer showed that if one of the 10,000 bacteria species connected to this tree changes how it's living it can produce a poison that kills the ash dieback fungi growing on a certain percentage of trees.
A single bacteria species can make that difference. Now think about changing the whole world for these creatures by replacing tree species and creating artificial forests by tree planting. We don’t know what will become of that forest, especially in a rapidly changing climate.
So now people are saying “oh, Peter Wohlleben wants to let forests live on their own, so where will we get our timber from?” What I am proposing is to let the native forests do their job because they’re good at it. They have the same goals we have: the don’t like it very hot or dry and they want to produce as much biomass as they can. That’s exactly our aims. The question is how do we have intact, healthy, resilient forests and how much timber can we take from such a forest without weakening it again? The first goal has to be that the forest remains.
I’m wondering if you could respond to some criticism. Your work and the work of B.C. scientist Suzanne Simard, who you cite in your book, has been critiqued for anthropomorphism, or giving non-human things human traits. Critics say thinking of trees as having friendships or as having parent-child relationships could mean that we miss important science because we're trying to fit these life forms into a human narrative.
How should these results be communicated if not in human terms? Intelligence, for example, is not even precisely defined, but for some scientists it seems clear that all this applies only to homo sapiens, all other species have an inferior form of the respective abilities. This is not scientifically correct, but anthropocentric. A correct narrative about trees would have to be in “tree speech,” but I don't speak that. Therefore, I communicate the latest state of research vividly, as, by the way, universities and research institutes increasingly do.
In 2021 B.C. was hit with a heat wave that killed 595 people, many who lived in urban areas that acted as heat islands. The horrible irony is that these urban areas were old-growth forests 100 to 150 years ago. Is there any way to bring the cooling power of trees back into these urban centres considering how a tree needs an underground community of trees related to it, and microbes and fungi to thrive?
It’s impossible to reconstruct a city forest to be the same as a primeval forest just as they once were, but reforesting a city is still heavily discussed in Europe. In Paris city council tried to cool the city using pipes that ran under the city. Now they're trying to make Paris greener. City streets on hot summer days that have trees growing on them are 20 degrees C cooler than streets without trees. It’s a serious health problem to live on a street without trees.
It’s a very hard life for trees to grow in a city, but it's also a good laboratory for native species of trees to see what they are able to withstand. If the conditions are bad but they're still growing it's good news: if they can grow in the city they can grow in the forest.
It's important to make cities green as fast as possible because that's our best air conditioner. I can't imagine a machine which is able to cool streets by 20 degrees C every hot summer’s day without any energy input. Plus trees are good for birds and mammals living in cities.
One final question. What impact have your books had so far? What are you hoping to do with The Power of Trees?
When it comes to industry, my book made them a little bit more aggressive. But that's not a bad sign. I wanted to let people know what wonderful beings trees are and how important they are for us. Many people now see what the forest industry is doing. Sometimes they do a good job, of course, and people appreciate what they are doing, but in many, many cases they are destroying our most important resource for fighting climate change.
That brings people to act locally, which gives me hope. I've gotten emails from local NGOs who are caring for their city’s forest. People are aware of how important every tree is.
I don't think my book will rescue the forest. But they will do a little part. I’m also very optimistic that we can handle climate change and we can have a good future.
So long as we have big intact forests we can restore them by letting them come back. We can fight climate change efficiently and we don't have to wait 50 to 100 years. We can start right now, on every single spot on Earth where trees are integral.
Even planting a single tree in your garden or in front of your office can make a difference.
Peter Wohlleben will be in conversation with Arno Kopecky at the West Point Grey United Church at 7 p.m. on Sunday, May 7. Get your tickets and a signed copy of 'The Power of Trees' via Eventbrite.