Something has changed. While deforestation is advancing in one part of the world, it is slowing in another: an explanation of the global, European and Italian figures on forests. Because cutting down trees does not always mean deforestation.
with contributions from Gherardo Chirici, Piermaria Corona, Raffaella Lovreglio, Marco Marchetti, Paolo Mori, Renzo Motta, Davide Pettenella, Raoul Romano, Luigi Torreggiani and Giorgio Vacchiano
Deforestation is caused by the felling of trees, but cutting down trees does not always constitute deforestation. To understand this apparent contradiction, we must first define what a forest actually is.
The reference standard is the FAO definition: a forest (or woodland) is an area of at least 0.5 hectares with trees capable of reaching at least 5 metres in height whose canopy "covers" at least 10 per cent of the ground. Urban parks, gardens and tree formations in agricultural settings (an orchard or an olive grove are not woodland) are excluded from this definition.
Cutting down trees does not always mean deforestation
The definition is necessarily complex because it must leave as little room as possible for subjective interpretation. It is in fact designed to be applied across a network of measurement points that are periodically visited by teams from national forest inventories, whose task is to estimate the size of the forest heritage of different countries.
Admittedly, there are states that use slightly different definitions: a minimum canopy cover of 20 per cent or even 50 per cent, or a minimum area of 0.2 hectares (as in the forestry law currently in force in Italy, the testo unico sulle foreste e le filiere forestali). But when data are reported to the FAO, everyone is required to comply with the same criteria. This is the only way to truly understand how forest cover changes over time: we cannot know whether there is more woodland in France or in Italy, or whether woodland in Italy is increasing or decreasing, unless we always use the same rules to define it.
Having clarified what a forest is, let us return to deforestation. Again according to the FAO, deforestation is a permanent change in land use — for example, when a woodland is converted into agricultural land, pasture, or an artificial surface. Deforestation therefore does not simply mean cutting down woodland, but preventing the woodland from regrowing.
If felling does not prevent the woodland from regenerating, it does not constitute deforestation: woodland areas that have been felled, affected by fires or destroyed by extreme weather events are defined as "areas temporarily without standing timber". This is not merely a semantic distinction: here, the trees will grow back. For example, not everyone knows that in Italy, after any woodland felling or damage caused by extreme events, there is a legal obligation to ensure the regeneration of the woodland — through seeds or shoots produced by the trees, or by sowing or planting new seedlings where necessary.
When we see a recently felled woodland, then, there is a high probability that it is already on the point of returning, provided that whoever felled it acted in accordance with the law and the recommendations of silviculture — the science of sustainable woodland management. The seeds are waiting to germinate, the seedlings are ready to grow, or the shoots will emerge from the stumps within a year, and within a few years will once again cover the ground. When this does not happen, we speak of forest degradation: a phenomenon as problematic as deforestation (albeit more gradual) and, like deforestation, unfortunately prevalent in tropical forests.
But where do we stand with regard to the state of the world's forests? We answer this question at three different scales: global, European and Italian.
According to the FAO's Global Forest Resource Assessment of 2015, the planet's forests cover approximately 4 billion hectares, or 27 per cent of the land surface. At a global scale, deforestation dominates: from 1990 to 2015, the world's forests decreased by 0.13 per cent per year — an area equivalent to that of Croatia. There is, however, a positive finding: the trend towards deforestation is slowing (7.2 million hectares per year in the period 1990–2000, 4.6 million in 2000–2005, 3.4 million in 2005–2010 and 3.3 million in 2010–2015).
The lesser-known finding concerns the geographical disparity of the phenomenon. In the forests of the tropical and equatorial belt of the global south, there is a clear problem of deforestation. In the global north (temperate and boreal forests), forests are instead expanding. The world's trees are changing at two speeds.
The role of forests in combating climate change is clear: the world's forests contain 296 billion tonnes of carbon, across trunks, branches and roots — an average of 74 tonnes of carbon per hectare of woodland. As a result of deforestation, we have already reduced the carbon stock in the world's forests by more than 11 billion tonnes over the past 25 years: a figure equivalent to the CO2 emissions of the entire world in a single year.
The primary cause of deforestation is the consumerist lifestyle, with unbalanced diets, as well as, in part, the growth of the world's population, and the consequent need for agricultural land to produce ever greater quantities of food through industrial farming and livestock rearing.Società italiana di selvicoltura ed ecologia forestale
The main reason for deforestation is a consumerist lifestyle with unbalanced diets, as well as, in part, global population growth, and the consequent need for agricultural land to produce ever-greater quantities of food through industrial farming and livestock rearing. By burning trees and eliminating any future possibility of photosynthesis, deforestation generates enormous CO2 emissions (equivalent to 10–15 per cent of anthropogenic emissions), which in tropical ecosystems risk triggering a vicious cycle: more emissions mean a warmer climate, more frequent droughts and wildfires, which in turn increase the number of trees that suffer or die as a result of climate extremes. And fewer trees means less photosynthesis: if the current trend continues, according to recent research, tropical forests will stop absorbing carbon around the year 2030.
In continental Europe, according to the 2015 State of Europe's Forests (Soef) report, the forest area covers 215 million hectares: 33 per cent of the land surface. Forests remove 372 million tonnes of CO2 per year from the atmosphere (7 per cent of emissions) and contribute 0.8 per cent to European GDP (approximately 103 billion euros).
And contrary to what is happening in the tropical belt, forests in Europe are increasing, both in area (+27 million hectares since 1990) and in biomass (from 123 cubic metres per hectare in 1990 to 163 cubic metres per hectare in 2015: an increase of 33 per cent). The expanded area and growth of existing woodlands have brought the total volume of wood present in European forests to over 35 billion cubic metres, up from 25 billion in 1990.
What has allowed this expansion? Perhaps massive reforestation campaigns, as in China, where in the five-year period 2010–2015 new trees were planted across 1.5 million hectares of land? No. In Europe this result has depended above all on the abandonment of rural areas, where woodland has "returned" to occupy its original habitat. It is a mechanism as simple as it is fascinating. The seeds of "pioneer" plants, carried by the wind or by animals, reach fields that are often no longer ploughed, sown or cultivated as generations upon generations of farmers lovingly tended them. Finding themselves on fertile soil with plenty of light available, the seeds germinate and begin to grow, pushing up through the layer of grasses and shrubs, first forming isolated clusters and then a proper woodland.
In Europe the positive result has depended above all on the abandonment of rural areas, where woodland has returned to occupy its original habitat. It is a mechanism as simple as it is fascinating.Società italiana di selvicoltura ed ecologia forestale
After twenty or thirty years, once the new woodland has developed its canopy, the seeds of other plants arrive — ones better suited to growing in the shade — while the pioneer species age without finding the conditions they need to reproduce. In this way, a new forest, made up of the plants best adapted to the climate and substrate of the area, has established itself on what for hundreds or thousands of years was a cultivated field. This is the process known in ecology as succession, and we can imagine it has taken place every time we walk through a wood and come across a dry-stone wall or a terrace, a witness to an agriculture that is no longer there.
According to the Soef, over 500 million cubic metres of wood are extracted from European forests every year. And here we face a second contradiction: in Europe there are very few virgin forests where humans have never made their impact felt, and in the majority of forests trees are periodically felled to use their timber or for other purposes. How is it possible, then, that forests are increasing both in area and in volume?
This is the result of the sustainable management of forest resources, developed and agreed upon by as many as 46 countries and the European Union. Management is sustainable because only a portion of the wood that trees produce each year through their growth (in diameter and in height) is used. It is a little like having a bank account that earns interest, and each year cashing in only some of that interest to buy food, clothes and travel: the result is that, while we support ourselves, the portion of interest not withdrawn is added to the initial capital, which thus continues to grow. To put it in numbers, against 522 million cubic metres cut every year in Europe's forests, those forests grow by as much as 721 million cubic metres. The ratio between growth and felling is therefore 1.4 to 1 (albeit with considerable variability from region to region).
According to the most recent document on the state of Italy's forests, the Raf – Rapporto sullo stato delle foreste e del settore forestale in Italia 2017-2018, Italy's forest heritage consists of over 9 million hectares of forest (1,900 square metres of woodland per inhabitant) and almost 2 million hectares of shrubland, scrubland and maquis. In some regions, forests represent the most widespread land use, covering more than half the territory in Trentino-Alto Adige, Liguria, Tuscany, Umbria and Sardinia.
In Italy, too, woodland is growing, rising in 25 years from 31 per cent to 38 per cent of the national land area. A growth that has been under way since the first half of the last century, as shown by a recent digital reconstruction of the 1936 Carta forestale d'Italia. Naturally, a forest is made up not only of the area it occupies, but also of the number and size of the trees it contains. Indeed, the biomass present in our woodlands is also steadily increasing. Starting from 855 million cubic metres in 1990, we are now at 1,385 million cubic metres, with an annual increment rate of between +0.6 and +0.8 per cent: well above the European average.
Naturally, a forest is made up not only of the area it occupies, but also of the number and size of the trees it contains
In Italy, too, the increase in forest area is mainly due to the return of woodland to marginal or abandoned areas, and in small part to reforestation carried out over the past 30 years. The increase in woodland, however, is not only associated with an increase in area, but also with the growth of trees within forests, whose volume rose from 113 cubic metres per hectare in 1990 to 150 in 2015. At the same time, although it is rather difficult to obtain accurate data on timber extraction, official sources report a decrease in the ratio between felling and increment, which fell from 48 per cent in 1990 to 39 per cent in 2010 (according to the Soef) and to 24 per cent in 2015, according to the Raf (see graph below).
Let us imagine for a moment that we are in the heart of any Apennine forest, and that we have a time machine at our disposal
This figure may seem surprising, especially to all those passionate about trees and forests who look with concern at what is happening in urban and lowland areas, where trees and fertile soil are in constant decline. But let us imagine for a moment that we are standing in the heart of any Apennine forest, with a time machine at our disposal: winding the tape back a century or so, we would find ourselves surrounded by a mosaic of cultivated fields, terraced hillsides, vineyards, pastures and scattered scraps of woodland, squeezed between one stretch of land and another.
If we fast-forward the time machine, we will witness the rapid filling of all the empty spaces, the advance of trees over fields that are no longer cultivated, the return of woodland to mountain pastures no longer in use, and the increase in the diameter and height of trunks in woods that already existed. We will see wolves roaming again, having taken advantage of the expansion of woodland to extend their territory; we will encounter more frequently the insects