La Massane: An open-air laboratory for the climate crisis

Just 10 kilometers from the Mediterranean Sea, in an enclave where the French Pyrenees Mountains meet the coastline, is the Massane forest, a place where the human hand has not intervened for 150 years and that in recent decades has attracted the attention of scientists. The uniqueness of this forest is the subject of scientific research in which individual monitoring of the evolution of its beech trees is being carried out and which, due to its relevance and thoroughness, is considered unique in Europe and the rest of the world.

Following the suspension of forestry activities in this area in 1886, the Massane, located in the Albera Massif, has evolved freely as a forest. This makes it, after more than a century without any human intervention, an ancient forest, a place where exceptional biological and ecological dynamics are generated. The study of these dynamics and the discoveries made, especially regarding the forest’s great genetic richness, are generating growing scientific interest due to their enormous value in the context of a climate crisis that is worsening every year.

When we first heard about this forest we decided to contact the Association des Amis de la Massane, which has been responsible for the scientific management of La Massane since it was recognized as a National Nature Reserve in 1973. We wanted to visit it because of its importance—it was declared a UNESCO World Heritage Site in 2021—and its scientific relevance; but, secretly, we were especially attracted by the mysteries that make this forest such a special place. 

On the agreed day, at the end of February, we set off at dawn from the coastal town of Argelès-sur-Mer and arrived at the meeting point, where our contacts were waiting for us. Jean-André Magdalou, currently head of scientific research at La Massane, and his colleague François Charles, a researcher at the French National Center for Scientific Research (CNRS) in the Banyuls laboratory, picked us up in their SUV and took us along forest tracks leading up into the mountains. With great enthusiasm, Magdalou began to tell us about the unique features of Massane. From the very beginning, his passion for his work and his desire to share it with others were evident. With these high spirits, we arrived at the point where the route continued on foot.

Forty minutes into our walk we approach the entrance of La Massane and feel a distinct physical change: the landscape suddenly shifts. Despite being so close to the Mediterranean, here the climate is more like that of the Atlantic. Average annual rainfall is around 1,200 millimeters, 60% greater than down the mountain on the coast. Vegetation more typical of Atlantic climates heralds the main feature of La Massane: a very old beech forest (la hêtraie) that survived the last Pleistocene glaciation, which occurred between approximately 100,000 and 10,000 years ago.

Magdalou explains that the Massane beech forest is, in principle, an anomaly, both because of its proximity to the Mediterranean and because it grows at a relatively low altitude of around 600 meters. But what has really attracted the attention of scientists is its astonishing biodiversity, in terms of genetic diversity and the high number of species in such a small area. The Massane National Nature Reserve covers only 336 hectares, of which 120 are covered by beech forest. Paleoecological studies carried out in the area have shown the age of the beech trees and their great genetic diversity, which in Magdalou's words, acts as a kind of “genetic reserve.” To date, at least 931 species of fungi and some 2,000 species of insects have been documented. This forest alone is home to a fifth of the estimated 10,000 species of insects in the whole of France—excluding its overseas territories. If we include plants, animals, and fungi, the Massane is home to some 12,000 species. As we walk through the forest, we become aware of just how astonishing these figures are. 

When a forest is left to its own devices, certain processes occur over the long term that would not otherwise take place. In the case of La Massane, the only external factors affecting the ecological dynamics of the area are cattle grazing and human activity in the form of hiking. For these reasons, after it was declared a National Nature Reserve half a century ago, scientists physically delimited the heart of the beech forest with a fence to protect it. This area is what they call an “integral reserve.” 

As we enter it, we gradually begin to appreciate its special characteristics. It appears as if the beech trees are a family. They tend to grow very close to each other, to a height of about 40 meters, forming a kind of umbrella at the top that protects the ground from direct sunlight, (serving to preserve moisture and prevent low vegetation growth); the roots intertwine in a way that makes visible the communication between the trees and their perception of the elements in the soil, such as nutrients, moisture, chemical composition, and acidity. Living trees coexist with dead trees which still rise high into the sky, despite having lost most of their branches. In their hollow trunks, shelter is provided for new forms of life. The ground is littered with dead wood, soaked with moisture, which crumbles in our hands like a vegetable sponge. It spreads, frays, and transforms into substrate. We notice how the soil is formed, the earth; we see the transition from the plant world to the mineral world. Living things are made inert, becoming the beginning and sustenance of new life.

This union between life and death is what ancient forests show us in the long term. The trunks are attacked by fungi that proliferate inside them, gradually converting the wood into mycelium, the roots of the fungus. Many species of fungi develop only as mycelium, and only some of them fruit on the trunk, producing mushrooms of great beauty; the image of multiform mushrooms emerging from the trunks is a characteristic of La Massane.

Fungi consume the dead trunk, feeding on it and producing what is known as humus. New biological dynamics take place inside it. The mushroom is attacked by a wide variety of species of coleoptera, chewing insects including beetles. This gives rise to a phenomenon characteristic of the site studied in detail: the saproxylic fungal procession of the beech tree, which is only possible in a dynamic of long-term “forest continuity.” That is, in a virgin environment where evolutionary selection continues to act in a pure manner, unaffected by external factors. What happens in the mushroom is that various species of beetles penetrate its interior; each species acts as a genetic variant that enables the emergence of the next species, as if it were a genetic procession. When we open the mushroom, we find a specific species of beetle at its core—the 27th since the procession began—which could not have emerged without the existence of the previous ones. This biological process is a good example of the genetic richness of ancient forests and highlights the importance of their free evolution.

The result of this interaction between dead wood, fungi, and insects is the production of substrate that feeds new forms of life. The trunks that once rose toward the sky end up decaying, their remains scattered throughout the forest accompanied by mushrooms and insects that continue to feed on their insides. The fact that there is no intervention of any kind in the forest favors the spread of a continuous layer of wood on the ground that helps conserve moisture. In this way, Massane protects itself from what is now its main threat: climate change.

A laboratory is usually understood as an artificial environment in which matter is studied under ideal conditions that, although they do not correspond to the spontaneous behavior of nature, can reveal its mysteries to us. Nature thus appears as a resistance to the desire for knowledge, as something that must be purified in order to obtain stable and valid knowledge.

This distinction between nature and laboratory, between spontaneous evolution and research apparatus, is blurred in the scientific research carried out at La Massane. Hence, the scientific community involved in the area refers to it as an “open-air scientific laboratory.” In a pioneering effort, the Massane beech forest has been monitored for decades, with the individual study of some 70,000 beech trees. Closely following the evolution of each tree is a novelty—because of the intention behind it and the dedication it requires—in approaching the evolution of nature.

As we walk through the reserve accompanied by Magdalou and François Charles, we become aware of the importance and richness of this research work. The condition and dynamism of each tree is studied in detail: its growth, its response to varying conditions of humidity, temperature, or pollution, and the adaptive strategies it develops to cope with the dangers that threaten it. Magdalou explains that one of the central issues they study in beech trees is the phenomenon of cavitation. If we understand a tree as a “column of water” from the ground to the treetops, cavitation consists of an interruption in the flow of liquid in the trunk and branches due to the tree's exposure to water stress. As an analogy, Magdalou likens it to an animal suffering an embolism. The consequence of a lack of water in the soil is that the tree sacrifices some of its branches. If the necrosis progresses, the tree as a whole enters a process of slow death that can last between 10 and 20 years.

The team of researchers has mapped the entire reserve, with precise data on the degree of cavitation affecting each tree, as we can see in the maps shown by Magdalou. This recording work is becoming particularly relevant in the current context of the climate crisis. Given its proximity to the Mediterranean, Massane is particularly threatened by the rapid and dramatic changes in rainfall and temperature patterns that are being recorded globally. Magdalou explains that changes in La Massane have accelerated since 2019, with below-average rainfall and record temperatures year after year. Every summer, the number of days with very high temperatures (above 30º) and the maximum temperatures reached in the reserve continue to increase, reaching 41.7º in the summer of 2023.

When we ask how he feels about the future of La Massane, Magdalou is not quite sure how to respond. His emotional attachment to this environment runs deep. After hesitating for a moment, he says he prefers to focus on La Massane's proven ability to cope with change. Obviously, there are no preconceived formulas for knowing what to do in the face of the climate crisis; IPCC data suggest that we have already entered uncharted territory. When discussing forest management, and especially how to prevent the sixth-generation mega-fires that are now a reality in regions with a Mediterranean climate, a model in which human intervention is essential is often contrasted with the model of free evolution represented by ancient forests. It is necessary to find the most appropriate formula for each particular case. However, places such as La Massane show the importance of paying attention to the self-preservation strategies that forests develop spontaneously. The European Regulation on Nature Restoration, approved in 2024, points more in this latter direction. And this invites us to share, not without fear, Magdalou's optimism.