Among the Sami of Finland, a newborn first sleeps in the komsio, a cradle made from several parts of a birch, as if the whole forest were taking it in its arms. At the very north of the world, the boreal forest covers a tenth of the planet’s land. Light and night, warmth and cold follow one another there, and every species depends on the others. The birch is not the tallest of its trees, but it carries a whole world, which warming is forcing to move.
The birch, “the most important tree in the forest”, provides every piece of the komsio, and each one protects the child.
More than a billion hectares: the taiga is the largest continuous expanse of vegetation in the world and holds almost a third of the land biomass.For the sculptor Sami Leiti, the birch seems neither special nor perfect at first sight, but whoever learns to know it makes it an ally: a branch becomes an oar, a straight piece with curved ends becomes a bow. Taking from the forest, he says, means thinking of its needs as much as one’s own. One day, his father took him to fell a huge, straight birch which, caught among the pines, was about to start declining. His grandfather had spotted it when his father was still a child, and rather than cut it down, they had decided together to let it grow. Years later, the tree yielded wood of exceptional quality, and the objects made from it will stay with the family for generations. Every decision, to harvest or to preserve, is weighed with others in mind. At the heart of the taiga, our birch is about fifty years old and thirty metres tall; the conifers look down on it and take the light. Yet it has lessons to teach them. It renews its leaves every spring and sheds them in winter so as not to be bitten by the cold. Its fine roots run close to the surface. Its white bark reflects the summer heat, holds the snow around the trunk and blends it into the landscape, out of reach of hares and reindeer.
“We could not exist without the forest,” says Sami Leiti: it protects against wind and erosion, and maintains the balance of nature.
For anyone who works with wood, the birch is an endless source of inspiration: each of its curves can give rise to an idea.
Rich in salicin, birch bark repels parasites; it can even peel away in thin layers to shed the boldest intruders.Herbivores do not just consume: they garden the forest. The ecologist Tamara Hiltunen follows the tracks of reindeer, so discreet they can barely be seen. As at a buffet, they take a mouthful here, another there. They trample the moss and open small gaps where light reaches the ground and a seed can germinate; their droppings fertilise the soil. One reindeer seems to change nothing, but the boreal forest has several million of them, and what we see today, they have shaped over the centuries. Despite the herbivores, the cold, the storms and the fires, the taiga always regenerates. The birch is its pioneer tree, “the hare of the forest”: its light seeds travel on the wind and make do with little. It reaches one metre in its first year, eight metres at five years. At forty, it has reached its full height; the conifers overtake it and plunge it into shade. It will live a hundred years at most, if a surprise guest does not hasten its end: the polypore.
For Tamara Hiltunen, removing an animal or a plant from the boreal forest has a cascading effect on the rest of the system.
A migratory species, the reindeer moves with the climate and the vegetation, from grasses to birch leaves, from flowers to lichens.
At fifteen, the birch already stands ten metres tall and keeps a good head start on the conifers.The mycologist Dmitry Schigel observes the mites moving across a tinder fungus, a common polypore of the birch: the fungus has profited from the tree’s life, and its own life now benefits the invertebrates. While alive, the tree defends itself chemically and holds the fortress. Once established, the polypore’s mycelium attacks the wood fibres for years, even decades, before fruiting. What we see on the trunk is therefore not the beginning of the story, but the end. People often see death in it; he sees a sign of health, of stability, of biodiversity. So discreet that it blends into the scenery, lichen too plays an immense role. The biologist Lilith Weber, of the Natural History Museum in Helsinki, points out that it is not an organism but a partnership: a fungus that protects and waters, algae that feed it with sugars. Lichen fixes nitrogen from the air and returns it to the soil. At the edge, where nothing else lives, it settles, and over the centuries a field of lichen becomes a forest. For her, it is a lesson: cooperating without exploiting one another, or exploiting the environment.
The polypore’s spores, much lighter than seeds, enter through the roots, the hollows of the trunk or dead branches.
A researcher at the University of Helsinki, Dmitry Schigel points out: without decomposition, the forest would not function; the decaying tree enriches the soil.
For Lilith Weber, hypogymnia, like many other lichens, prefers birch bark, which is less acidic than that of conifers.
In the subarctic region, a great variety of lichens remains to be discovered: a diversity that is “totally unexplored”.In winter, the birch almost empties itself of water so as not to freeze, and under the gusts, supple, it bends and straightens up again while the rigid conifers snap. As they fall, they carry away one world and create others. A professor at the University of Eastern Finland, Tuomas Aakala studies these windfalls: the bare soil, the gap in the canopy, and already a birch shoot that would never have germinated in the shade of the spruces. On the island of Jouhteninen, a storm felled the trees on half the island; the uniform pine forest has given way to a rich and varied one. But the climate is changing faster than the forest. The birch adjusts its growth, regulates its transpiration and sends northwards seeds capable of travelling a hundred kilometres or so; its future remains uncertain. The activist Jarmo Pyykkö points out that in Finland only 5% of forests remain in their natural state. Left to itself, the boreal forest stores carbon for thousands of years: “a cold store of carbon”, which empties as the climate warms. With scientists, he maps the forests and secures their protection.
In the rings of fallen trees, Tuomas Aakala reads their history: one spruce more than 35 metres tall had grown for 180 years before falling.
Long regarded as disasters, storms now appear as a key element in the development of the whole forest ecosystem.
According to Jarmo Pyykkö, specialists estimate that half of the boreal forest would need to be protected for it to function properly.“We are its children. We can either destroy it, or learn to live with it.”Sami Leiti, sculptor
“L’arbre qui cache la forêt is fascinating. […] The series goes beyond the trees themselves and the forests it depicts, to remind us of the complexity and importance of these ecosystems.”Mònica Planas Callol, Ara (Barcelona)translated from Catalan · July 2026
“Sumptuous images, a dreamlike voice-over, a hypnotic soundtrack […]. Beneath the trees, we marvel at the intertwining of the infinitely small and the infinitely large. […] By celebrating the majesty of the setting, L’arbre qui cache la forêt urges us to preserve it.”Ouest-FranceJune 2024