If one tree carries the soul of Euskal Herria, it is the oak. From assemblies under broad canopies to today’s scattered giants in meadows and mountains, oaks have been our shelter, our timber, our emblem of freedom. Their story is both cultural and ecological: a symbol of self-governance, a witness to centuries of use and destruction, and still today a keystone for biodiversity on both sides of the Pyrenees.
The oak of Gernika: law under branches
The best-known oak in the Basque Country is the Gernikako Arbola, the oak of Gernika. Since the Middle Ages, representatives of Bizkaia met under its branches to swear laws and charters. In 1512, Gernika became the permanent seat of the General Assemblies, and since then kings, regents, and modern lehendakaris have taken their oaths beneath its branches.
But oaks are mortal, even sacred ones. The original tree lived about 450 years before being replaced in 1742. Its successors lived through wars and industrial change; the trunk of the “Old Tree” is still preserved in a shrine beside the Assembly House. A later oak famously survived the 1937 bombing of Gernika, only to succumb to disease decades later. The current tree, planted in 2015, is the fifth in the line—direct descendants, replanted each time.
When the oak of Gernika dies
That the oak of Gernika has died again and again is more than a botanical detail. It can be read as a symbol. Just as the oak represents Basque freedom and continuity, its repeated decline can be seen as a mirror of something larger: the slow erosion of both nature and culture when we do not tend to them.
Each Gernika oak withered for a reason—fungus, disease, humidity, or exhaustion of the soil around its roots. Those are not accidents. They are reminders that even a sacred tree depends on healthy surroundings. When soils are compacted, when air is polluted, when the ecosystem around a tree is weakened, its lifespan shortens.
In this sense, the cycle of death and replanting is not just tradition—it is a warning. If even the most protected oak in Euskal Herria struggles to survive, what does that say about the countless oaks scattered in fields, valleys, and hillsides with no fences or caretakers at all?
The Gernika oak is renewed because people care enough to plant its offspring. But outside the Assembly House, countless oaks have no heirs. The health of that symbolic tree is not separate from the health of the wider ecosystem—it is an indicator. When oaks thrive, so do we. When they fail, it tells us we have work to do.
Oaks across Euskal Herria: from common to scattered
Historically, oaks covered much of Euskal Herria. Pedunculate oak (Quercus robur) dominated lowlands, Pyrenean oak (Quercus pyrenaica) flourished in Álava and Navarra, while holm oaks (Quercus ilex) dotted drier slopes of Nafarroa Beherea and Lapurdi. Acorns fed livestock, beams built ships and farmhouses, bark tanned leather, charcoal fueled forges. They were so useful that oak groves shaped rural life for centuries.
That usefulness also caused their decline. By the 19th century, centuries of felling and grazing had reduced oak forests to fragments. The Atlantic valleys of Gipuzkoa and Bizkaia were rapidly converted to pasture and later to pine plantations. In the north, old holm oak groves on limestone cliffs gave way to vineyards or quarries.
Today, only a fraction of these oak woods remain. In the Basque Autonomous Community, just under 30,000 hectares are still oak forest—barely a remnant compared to their former spread. In Iparralde, too, the patches that survive are often isolated, hemmed in by maize, urban sprawl, or exotic plantations.
One exception is Izki Natural Park in Álava, home to the largest continuous Pyrenean oak forest in Europe: around 3,500 hectares. Here, oaks still dominate valleys and hillsides, hosting Spain’s densest population of the Middle Spotted Woodpecker—a bird that depends on mature, rough-barked oaks.
Why old oaks matter
Young oaks are valuable, but old oaks are irreplaceable. Their wide canopies, hollow trunks, and ancient bark host hundreds of species: fungi, beetles, mosses, bats, owls. Acorns feed wild boar, jays, and doves; fallen branches nourish soils; shade keeps streams cool. A single tree can act as an entire ecosystem.
Across Euskal Herria, scattered veterans survive: lone pollards in meadows, boundary trees on farms, sacred groves near villages. They are living archives, shaped by centuries of cutting, storms, and survival. Protecting them means protecting not just a tree but entire food webs.
The pressure of invasive species
If centuries of overuse thinned the oaks, today new threats crowd them out. In Bizkaia and Gipuzkoa, radiata pine plantations have long dominated, but disease in pine has driven a rapid expansion of eucalyptus. Since 2005, eucalyptus cover has doubled in the Basque Autonomous Community. Eucalyptus grows fast and produces pulpwood quickly, but it also consumes huge amounts of water, dries out soils, and sheds litter that decomposes slowly—reducing nutrients for rivers and streams. Local studies show eucalyptus plantations support far fewer bird species than native forests.
Other invasives are spreading too. Ailanthus altissima (tree-of-heaven) springs up along roadsides and quarries, releasing chemicals that suppress other plants. Robinia pseudoacacia (black locust) alters soils and crowds out native saplings. Left unchecked, they block oak regeneration, turning once-diverse woods into monocultures of low ecological value.
A symbol for culture and ecology
For all these threats, the oak endures—in patches, in parks, in memory, and in the logo of Rewilding Euskal Herria. We chose the oak not by chance, but because it embodies both cultural continuity and ecological resilience. It reminds us that identity is rooted in landscapes, and that freedom requires healthy ecosystems to stand on.
Oaks connect all provinces of Euskal Herria—from the pollard fields of Nafarroa, to the Pyrenean oak forests of Álava, to the holm oaks of the Lapurdi cliffs. They cross borders just as rivers and birds do. Protecting them is not only conservation—it is a statement of belonging, across the whole land.
Looking forward
The oak of Gernika shows us that symbols must be replanted again and again to endure. The same is true for the real forests that once covered this land. Centuries of overuse and recent invasions have left scars, but resilience remains. Every surviving old oak, every acorn sprouting in a meadow, every grove that regenerates, is part of a living chain that ties us to the past and to the future.
To care for oaks is to care for Euskal Herria itself. They are more than trees: they are shelter, food, memory, and the foundation of healthier landscapes to come.
That is the work ahead of us. Rewilding Euskal Herria exists to give these living symbols the space and strength they need. Supporting this effort—by valuing nature, by speaking up for it, by helping it grow—is the best way to ensure that the oaks of tomorrow will not only survive, but thrive.
