Italy planted millions of fir trees to protect the Alps. 90 years later they have discovered that biodiversity has been reduced by half

The ecologist Aldo Leopold wrote a phrase that would end up defining all modern conservation in 1949: “maintaining each piece is the first rule of ecological intelligence.” He said it decades before science could measure it, but today studies like the one in the Alps Italians demonstrate the extent to which removing pieces of an ecosystem can seem invisible… until generations pass.

A forest that seemed like a solution. In the 1930s, Italy by Benito Mussolini He decided that the best way to stabilize the Alps was to cover them with trees. The logic seemed impeccable: stop erosion, ensure wood for the future and display an image of order and national productivity.

For this they chose norwegian sprucea fast-growing conifer, straight trunk and profitable wood. Thousands of hectares of alpine meadows and native forests were razed to plant dense, homogeneous rows of this species. For decades, that decision was sold as a forestry engineering success. From afar, those green forests looked healthy. But almost a century later, science has discovered that beneath that appearance a silent impoverishment was hidden.

Ninety years later, the ecological bill. The studyled by ecologist Gianalberto Losapio and published in the journal Ecology, analyzed two areas of the Italian Prealps, near Lake Como: Monte Bisbino and Vicere Alp. There, the researchers They compared three habitats Neighbors: spruce plantations, native deciduous forests and traditional alpine grasslands.

During five months of field work they identified 136 plant species and 201 arthropod species. The results were devastating. In plantations there was a median of only seven plant species per plot, compared to 18.5 in native forests and 37 in grasslands. Translated: more than 50% less diversity than in natural forests and almost 75% less than in the pastures.

The problem of planting only one type of tree. The big mistake was believing that more trees automatically equaled more nature. Monoculture works well to produce wood, but It’s an ecological trap. When a landscape is filled with a single species, complexity disappears, because each plant, insect and microorganism plays a role in the ecosystem.

Reducing this variety implies reducing resistance to diseases, pests or extreme phenomena. In the Italian Alps, diverse landscapes were replaced by uniform blocks coniferousand the result was a brutal simplification of the ecological network. What seemed like reforestation ended up being a substitution of biodiversity for productivity.

Darkness as a silent weapon. The norway spruce It has a key characteristic: it is perennial. While beech, maple or chestnut trees lose their leaves and allow light to reach the ground in spring, the spruce maintains a closed canopy all year round.

It is not trivial. In fact, that difference changes everything. Many alpine plants flower precisely in that window of early light, before the forest canopy closes. Under a spruce plantation, that opportunity disappears because the ground remains in constant shade and many species simply cannot survive. That is, it is not an open competition, it is a physical and permanent exclusion.

The ground was also transformed. There is more, because the damage did not remain on the surface. Spruce needles acidify the soil as they accumulate over decades. The researchers found 25% more organic carbon in these plantations, although that did not mean greater fertility. It was just the opposite: organic matter decomposed more slowly, a sign of lower biological activity.

Not only that. The balance between carbon and nitrogen also I was upsetindicating slower and less efficient nutrient cycling. In simple terms, the forest continued to accumulate remains because the system had lost the capacity to recycle them. It was a stuck ecosystem.

A poorer and more fragile forest. Beyond the number of species, scientists measured something even more important: the “functional uniformity”that is, how ecological roles are distributed within the plant community. In spruce plantations, this index was 30% lower than in natural forests.

That means less balance and more vulnerability. It’s not just that there are fewer species, but rather that entire functions within the system are missing. Some niches were left empty and many ecological jobs stopped being done. In other words, the forest is still there, but it works worse.

It didn’t even create a new ecosystem. The researchers of the study said that one of the most revealing findings was verifying that these plantations they did not generate a new community adapted to the spruce. In fact, no specialized boreal species appeared nor a new equilibrium built.

No, what they found was a version mutilated of the original forest: the same species as always, but less numerous and diverse. The spruce did not bring new life, it simply eroded what already existed.

The insects resisted better, but with nuances. The only less alarming data appeared in the soil arthropods. Its diversity barely varied between plantations and natural forests. Reasons? Scientists believe that this due to their mobility and their ability to move between nearby habitats.

Be that as it may, even here there is caution among experts. Soil chemistry suggests that microbial activity and the finer network of underground life have also changed, although they were not directly measured. The surface may give an image of partial recovery, but the subsoil continues to tell another story.

The global lesson that comes too late. If you also want, what happened in Italy is not a historical rarity. Today, a good part of the global reforestation commitments continue exactly this model: plant quickly, cheaply and uniformly to meet climatic and accounting objectives. According to previous studies cited by the authorshalf of the areas committed to forest restoration in the world are monocultures of non-native species.

Although it is an efficient formula in the short term and tempting for governments and companies, the experience of the Italian Alps shows that the ecological cost takes decades to appear, and that when it does, it is already it’s too late. The trees still stand and the shadow continues to block life.

And ninety years later, many of the species that were expelled still have not returned.

Image | Bernini123, PXHereGoogle, Maxar Technologies

In Xataka | There are scientists deliberately causing earthquakes in the Alps and they have a good reason for it

In Xataka | One of the biggest mysteries of the Himalayas was in its geology: we have just discovered that it is “destroying” the Earth’s crust