Many of the plants growing within the Goccia forest thrive on poor, stony, and abandoned soil. And it couldn't be otherwise, given that this urban forest—which borders the neighborhoods of Quarto Oggiaro, Villapizzone, and Bovisa, north of Milan—stands on what was an industrial site for nearly a century, starting in 1908. More specifically, a site for the production of gas from coal distillation, needed first for city lighting and later for domestic and industrial uses. For just over three decades, since the final decommissioning of the so-called "Gas Works" in 1994, greenery has been reclaiming its space, giving rise to a forest enclosed by the concrete walls that surround the Goccia, hiding it from the view of passersby.

Of the more than thirty hectares that make up the Goccia area, so called because of its distinctive shape when observed from above, approximately 18 will be dedicated to the enhancement of the forest that has made its way between industrial buildings, cast iron manholes, concrete platforms that housed coal loads arriving by train, and huts that in more recent times housed a few dozen squatters. This forest, growing on patches of asphalt and contaminated by various waste products from coal processing, will undergo an experimental remediation process using the tool of 'bioremediation'.

"We're actually inside a forest, but formally it's a polluted area undergoing remediation," explains Gabriele Galasso, a botanist at Milan's Civic Museum of Natural History. Galasso, along with his colleague Lara Quaglini, accompanies me on a tour of a place still off-limits to the public, but which for many years has been visited, more or less unauthorized, by the curious and groups of Urbex (urban explorers), often drawn to the ruins of the industrial architecture. The silhouettes of the two gasometers have become the very symbol of Bovisa and its industrial past. We enter the Goccia through the northwest entrance, on the opposite side from the construction work, which instead affects the area closest to the gasometers, and where the railway tracks separate Bovisa from the Villapizzone neighborhood. This is where coal loads destined for distillation once entered. Today, however, plants and flowers that thrive in abandoned places grow spontaneously and have found their ideal habitat in this post-industrial landscape: mullein, which grows in cracks in the asphalt and is covered in hairs to protect itself from the sun's rays and dehydration; saxifrage, a protected species, once widespread along Milan's ramparts and now surviving only in railway areas and marginal contexts (such as, obviously, the one we find ourselves in); and South African ragwort, an invasive species that exploits railways and other transport routes to spread, adapting, as Galasso explains, "to situations of great stress and environmental degradation."

Gabriele Galasso, Botanico del Museo Civico di Storia Naturale di Miano

And then there's Petrorhagia dubia (also known as velvet carnation): a plant that thrives in abandoned places, poor, gravelly soil with a high water content. It was found here for the first time in Lombardy, being a typical Mediterranean plant (and may have reached Bovisa due to global warming or brought by human activity). For these reasons, Petrorhagia dubia will soon be the subject of a publication in the scientific journal Natural History Sciences, the scientific journal of the Civic Museum of Natural History in Milan (published since 1870, but previously known by the more archaic name Proceedings of the Italian Society of Natural Sciences). Among the many plants that appreciate this post-industrial landscape and contribute to its rebirth, others emerge that, instead, represent the historical memory of the Milan area and have populated it since before the city itself, around the 5th century BC. This is the case of the wild orchid (Cephalanthera longifolia): a native plant whose spread in these parts predates both the industrial and agricultural eras.

Observing the stone crusher and the many other plants capable of tearing through the asphalt and taking over abandoned buildings, the imagination runs to a possible future, a la The Last of Us or other post-apocalyptic tales, in which the Milan area is reconquered by the forests that once flourished here before human settlement:

"The Milan area was covered by a forest consisting, below the watershed line, of English oaks, hornbeams, and field maple; while above, where we are now and particularly in the woods of nearby Affori and Bruzzano, there were mainly sessile oaks and another type of oak, similar to English oaks but more suited to soils lacking in water," explains Gabriele Galasso.

The line of springs (water sources typical of the South Milan Agricultural Park) marks the transition from the upper to the lower Po Valley, where the soil changes from gravel to clay. In the upper Po Valley, rainwater percolates through the gravel, accumulates in the aquifer, and then, encountering the clay layer of the lower plain, naturally surfaces in the form of springs. Beginning with the arrival of the Cistercian and Carthusian monks around 1100, these springs allowed for the development of water meadow cultivation techniques, paving the way for livestock farming in the Po Valley, the production of abundant hay, and, consequently, the birth of Grana Padano cheese.

It is for this reason that the southern area of ​​Milan remained agricultural for a long time, and in part still remains so today, while the northern area was the first to industrialize. A different fate, of which the native trees present in the Goccia—there are no oaks, but there are cherry trees and even maples—preserve the memory of the lowland forests. However, the Bovisa forest is not only home to native species; on the contrary: "We have counted around 250 species; the number of native species was higher than expected, while in the municipality of Milan we usually find a lower number," continues the botanist from the Natural Sciences Museum. "The number of exotic species, which is around 25-30%, is also higher than expected, but it is a value similar to what we find in the rest of Milan and the Po Valley, where exotic plants are brought by the movement of people."

Among the alien species that have found a home in the Drop, some are invasive and invasive, capable of altering the ecological balance and rapidly occupying the vacated spaces. This is the case of the tree of heaven, a tree native to China included in the European Union's blacklist for its highly aggressive nature: its roots release substances that impede the growth of other plants. "For now, it only grows residually inside the Drop," Galasso continues. "But we must be careful, because it spreads easily and eliminating it is very complex."

Another example is the aforementioned South African ragwort: a herbaceous plant that uses communication routes—railways, roads, mountain trails—to spread and easily adapts to situations of severe environmental stress. "As is the case with many exotic species, it is assigned invasive species status because it can have negative impacts on native species, infrastructure, or even health," Lara Quaglini explains. But studies confirming these effects are often lacking. For this reason, we conducted and published research to evaluate the ecological impact of ragwort on soil flora and microorganisms, but we found no significant effects. Of course, it can become locally abundant, but it tends to appear where vegetation is sparse: once the environment closes in, it can no longer compete. In any case, being toxic to humans and livestock, it must be kept under close surveillance.

Sono circa 250 le piante censite alla Goccia

In addition to monitoring the spread and harmfulness of invasive species, it is crucial to monitor the remediation process. As mentioned, this process is also occurring through natural processes, and significant positive signs are already being identified. One such process is the presence of Cladonia rei in the heart of the Goccia forest: a lichen species that cannot grow in contaminated soil, and its presence indicates that at least a portion of the soil has been naturally remediated and requires no further intervention. The experts who manage the Goccia are studying how the plants themselves, with the help of fungi and bacteria, can contribute to the remediation of the area by absorbing and metabolizing hydrocarbons and heavy metals. Understanding the dynamics of this process, known as bioremediation, will help decide if, where, how, and how much to intervene with natural solutions.

“Milan was once considered a ‘lichen desert,’” explains Galasso. "The presence of lichens here, in various species, means that the air is clean of oxides." This is also confirmed by the presence of Bacidina adastra, another lichen species first identified in the Goccia in Lombardy.

As we enter the increasingly dense forest, we encounter clematis, a liana native to the area; brambles producing blackberries; ferns that likely grew inside abandoned buildings and then found new habitats in the forest; wild chicory, characterized by its blue flowers that open only at the beginning of the day and then close again when the heat rises; the parasitic plant phelipanche, with its showy flowers resembling small orchids; and also wild barley, mallow, meadow cornflower, mint, and even trees known as "pioneer" trees, because they are capable of rapidly colonizing disturbed soil, such as poplars, elms, and black locust trees.

Some find their ideal habitat in the center of the forest, but many other plants, as we've seen, prefer poor soil and sun, concentrating where there are wooded meadows and clearings. And to allow their permanence, and thus enrich biodiversity, the forest must be actively managed, as Galasso and Quaglini explain to me: "The plants that appreciate these spaces risk being eliminated when the forest expands and fills the clearings. In nature, when trees fall, clearings are created and the natural cycle restarts, but in limited areas this phenomenon is relatively blocked. If we want to maintain these environments and preserve biodiversity, we need to remove patches of moss and grass from time to time to restart the cycle; otherwise, within 10 or 20 years, it will all become forest, reducing the number of species. Biodiversity, on the other hand, is the sum of environments and the species that populate them; if it becomes a single environment, biodiversity will necessarily be lower."

Le margherite della Goccia

This biodiversity is also contributed to by the fauna that characterizes La Goccia, where numerous animals have been observed: foxes (arriving from the north following the railway), tawny owls, buzzards, hedgehogs, woodpeckers, grass snakes, and owls. This fauna has found shelter in a forest that once stood where there was concrete and coal.

Unlike other green spaces recently created in Milan, La Goccia's forest is not an Instagrammable place, but one to wander through and contemplate: a space partially saved from real estate speculation and the ambitions of those who tried to label an "urban void" what is actually a forest that grew spontaneously in the industrial outskirts of Milan, populated by hundreds of plant species and numerous animal species. And it symbolizes nature's ability to regenerate, in an exceptionally short time, those industrial wastelands that, unknowingly, we abandon to its care.