National Tree Day, November 21st

Cirk 12 billion trees on 11 million hectares, i.e 36.7 percent of the territorial surface Italian national (2015 data from the latest National Forest Inventory, which is published every ten years). Are they friends to celebrate on November 21st next, on the occasion of National Tree Day.

Trees are our guardians

These traveling companions of ours on the planet are actually older brothers to whom we are indebted: they appeared in the Devonian, between 416 and 360 million years ago, allowing the first humans, about 200 thousand years ago, to find breathable air and to exist. In Italy, there are four superstar specieswhich cover 50 percent of the volume of our forests: beech, spruce, chestnut and oak.

«The tree is immobile, eternal and silent. It occupies space vertically, from the depths of the earth in which it immerses its roots up to the sky which it almost seems to touch, rising up to 100 meters high, turning its branches towards the sun and the wind. It doesn’t speak, but we continue to discover new ways it communicates and collaborates with neighbors through roots and leaves.” Dominique Roques, author of the book, writes with great poetry The scent of the forests. A sensorial journey to discover trees (Feltrinelli).

As a young man, Roques was a lumberjack, that is, someone who cut down trees, before becoming an essence hunter for the perfume industry. And with full knowledge of the facts he says that «the forests smell of the breath of the plants, of the flowers and fruits that open and disappear, of the roots that move in the ground, of the water that passes through them, of the sun that warms leaves, needles and trunks”. The enchantment and magic of the forest, which we all experienced as children.

Trees don’t speak, but they know how to communicate

Trees are extraordinary living beings. «They don’t have vocal cords to speak nor a neural system like humans and animals, but they have developed the ability to use chemical and electrical signals to communicate and defend oneself» explains Francesco Ferrini, professor of general arboriculture and tree cultivation at the University of Florence. «If they suffer damage, they release compounds that are detected by surrounding plants, triggering a defense response in them. The tree also knows how to use the right chemicals to attract pollinators. The scents of tree flowers are not always pleasant. For example, the flowers of the pear, hawthorn, carob or chestnut do not have a pleasant smell for us, but they attract insects useful to the plant.”

Direct wars and forced coexistence with insects

There are trees that are true champions in the art of war. An example? L’Acacia drepanolobium which lives in the East African savannah. This tree, which resembles an insignificant bush, has long thorns at the base of each leaf tuft. Some come out of a sort of ball full of little holes. Just give the plant a shot to understand what they are for. «Hundreds of ants come running out of the swollen thorns, ready to defend the tree» says Jonathan Drori, WWF ambassador and author of Around the world in 80 trees (The hippocampus). And while they shake, the ants exude pheromones that attract other defenders. What do ants gain from it? A house – the balls that host them – and sweet nectar offered to them by the plant.

Other trees choose chemical warfare. L’Azadirachta indicates it is an Indian evergreen, with beautiful fruits that resemble olives and tender leaves: an irresistible temptation for insects. Yet, everyone stays away from it. The tree is capable of synthesizing and introducing steroid-like repellents into the leaves, fruits and bark, which can modify the life cycle of insects. The flower and its nectar, however, lack it, thus inviting pollinators. From this tree it is obtained neem oil, now widespread in Italy as a natural insecticide.

A similar mechanism is used by horse chestnuts capable of resisting the attack of a small butterfly, the cameraria. «This insect is devastating the horse chestnuts of our country (Aesculus hippocastanum L.), while the American varieties with red flowers are spared» explains Ferrini. “The reason could be of chemical origin: the presence of a repellent in the leaves which makes them not attractive to the cameraria.” This defense ability is often the result of long coexistence with the aggressor: in the end, in order not to succumb, the tree develops its chemical weapons.

“There is a beetle, the emerald minercoming from Asia, which is wreaking havoc on ash trees in the United States» continues Ferrini. «It has been reported in Russia, and there is a risk that it will reach us too. Against this aggressor, American and European ash trees succumb. When the tree is under stress, for example in the event of drought, it emits volatile organic compounds which end up attracting the attacker. In China, however, its “cousin” Fraxinus mandschurica has always coexisted with this insect and has developed a natural repellent, which limits the damage.”

The value of biodiversity

In addition to parasites that increasingly travel in a globalized world, even extreme events – from drought to floods – they are a new challenge for our trees. As we saw in the dry summer of 2022, trees defend themselves from water shortages by losing their leaves earlier than necessary, blocking evaporation from the leaves. It is up to us humans, who have caused global warming, to study strategies to help these allies of ours. Replant as many trees as possible, even after an extreme event, trying to make them more resistant.

For example, in the city, good management and respect for the plant – no parking on its roots – prevents it from weakening. As for forests, for business reasons we often focus on monoculture. «In nature there are also forests of only larches or only firs» comments Ferrini. «But biodiversity is a value, for the forest and for human health. If we continue to attack nature as we are doing, by 2100 we will reach a 17 percent loss of biodiversity. Our actions today impact future generationswe must reverse the trend.”

The concept is simple: in nature different trees that coexist in the forest can help each other. Adult plants through the mycorrhizal network (the symbiotic bond between a plant and a fungus) help the younger ones and exchange useful substances. Suzanne Simard’s research has amply demonstrated that a forest made up of pines and alders is healthier. When the lumberjacks removed the alders to make room for the pines, which are more useful for timber, instead of getting better, the pines weakened: they lacked the exchange of precious substances through the roots.

Forests must be managed sustainably

Another mistake was to remove trees from agricultural fields, to have more productive land. «According to recent research, the trees in the vineyards improve the quality of the wine» says Ferrini. «They promote biodiversity, including predatory insects, and the improvement of the microclimate, so fewer treatments against parasites are necessary. Trees and country hedges are also a refuge for birds that prey on insects harmful to crops. After decades of enthusiasm for agrochemicals and herbicides, we need to rethink our agricultural model, recovering useful ideas from the past.”

Wood has accompanied human history since the beginning: using it to produce furniture or floors is a way of containing the carbon dioxide that has been stored in the trunk. It is very different, however, when the wood becomes pellets or logs to be burned. «In the face of fossil fuel pollution, wood has been repurposed as a panacea. A renewable and non-polluting source. But that’s not really the case: burning wood is a source of fine dust, particulate matter and CO2 which returns to the air. And the forest does not regenerate in an instant, it takes years for young plants to be able to store carbon dioxide like the older ones. You need to know how to manage the trees in a forest in a sustainable way: eliminate the weakest old plants, encourage the growth of healthier ones with rotational cuts, manage the undergrowth to avoid fires. However, it is a mistake to cut everything indiscriminately to obtain more quintals of wood.”

The project Forest me Go on

Trees are also our allies in the reclamation of polluted land. «Willows and poplars, which are fast growing, are very effective» explains Ferrini. «Trees can intervene in different ways, extracting pollutants and retaining them in their tissues, or in the roots where they are transformed into non-toxic and harmless compounds. In the case of hydrocarbons, they can be degraded with the help of microorganisms and even mycorrhizal fungi. Ultimately, the broken down pollutants can be put back into the air.” Certain, to “clean up” land with trees it takes up to 30 years, as long as the pollution is not serious. If a chemical company has buried a large amount of pollutants, they certainly can’t work miracles. Climate change is also increasingly affecting trees: they can die from drought or “drown” from excess water, which causes the roots to rot.

The good news is sensitivity is growing everywhere. Millions of mangrovestells Dominique Roques in his book, they were planted to protect the coast of Senegal. The Brazilian photographer Sebastião Salgado had two million plants planted in the 700 hectares of cleared forest he purchased.

China has been working for years on a Great Wall of trees to curb the desertification of the soil. Scientists are also working to save trees that are at risk of extinction: the Wollemi pine, discovered in 1994 in a mountain gorge near Sydney, has only 100 surviving individuals in the wild. Australian botanists have bred a collection of seedlings that they are distributing to various botanical gardens around the world to ensure their survival.

They are virtuous examples, in contrast with the deforestation of vast areas of the globe, which unfortunately continues. Here, Forestami continues its goal of planting three million trees by 2030, also involving citizens in collective plantations. According to Legambiente’s Forestry Report 2021, from 1990 to today in Italy there have been over 1 million more hectares of forest. On average, 800 m2 of new forests per minute. There is hope.

Our brothers Trees

The new book by botanist Stefano Mancuso (with Philip Giordano) is dedicated to the little ones. How did the first plants on Earth arise? AND How long can trees live? What tricks do flowers use to attract and force pollinating insects to take a “shower” of pollen? Why is the Amazon forest a green treasure chest for the planet? The book answers these and many other questions The fabulous world of plantsjust released by Aboca (20 euros), which was born from a happy synergy between the illustrator Philip Giordano and the plant neurobiology expert Stefano Mancuso.

The scientist here sets aside academic language to tell the world of plants to children with simplicity, arousing curiosity. Trees become superheroes, capable of crazy feats. Like that of the orchid that disguises itself as a female wasp to attract male wasps, and knows how to do it so well that they fall for it, acting as involuntary delivery boys for its precious pollen to other orchids.

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