An international project led by researchers from the University of Bologna has encrypted at 73,300 the number of tree species that currently exist on Earth.
And 9,000 of them are still to be discovered.
The census is the result of a three-year effort, the first large-scale estimate of global forest biodiversity.
The conclusions are published on Monday in the last issue of PNAS magazine.
The authors point out that the richness of terrestrial ecosystems is greater than estimated and, at the same time, recall that it is extremely vulnerable to changes caused by the human being (deforestation, loss of biodiversity and climate crisis).

“So far, data relating to many large areas of the planet were very limited and were based on the observation on the ground and in lists of known species and their distribution by zones; These same limitations prevented a global perspective on the subject,” he explains
Roberto Cazzolla Gatti, professor of the Department of Biognical, Geologic and Environmental Sciences of the University of Bologna and the first author of the study.
“A broad knowledge of wealth and the diversity of trees is essential to preserve the stability and functionality of ecosystems.”

But at the same time the authors emphasize that reaching a global perspective is complicated by different reasons: financing, logistics, field research or debates related to taxonomy are just some of the variables that come into play.
To overcome these obstacles, the researchers began gathering the most extensive databases until they made over species of forest trees, a cartographic operation that identified approximately 40 million trees belonging to 64,000 known species.
It involved 150 scientists from all over the world and was carried out within the framework of the Global Initiative for Forestry Biodiversity (GFBI).

Based on these preliminary results, scientists conducted statistical analyzes using artificial intelligence and the supercomputer of the Advanced Computer Laboratory (FACA) of the University of Purdue in Indiana (USA).
Once the calculations are completed, the researchers established that total number of more than 73,000 arboreal species, 14% more than those currently known.

“Conducting a census of the number of global species is like a puzzle that has pieces distributed all over the world,” says Professor Jingjing Liang, GFBI coordinator in Purdue and co-author of the article.
“In the GFBI we have resolved it as a team, sharing each of the pieces, we have combined the individual data sets, coming from the people who do the fieldwork-adgent that moves to the forest masses and measure each tree-,
In a huge set of global data “.

So, according to these results, there are still 9,000 unknown species, a third of which would be rare species with a reduced population, both in number and surface.
The authors believe that a large part of these species to discover (40%) could be in South America, more specifically in the two great types of landscape of the subcontinent: the “prairies, sheets and bushes” and “tropical and subtropical forests”
of the Amazon and the Andes.

“To obtain a reliable estimate of biodiversity, you have to pay attention to the number of rare species that are currently known, those that have appeared one, two or three times in field samples,” analyzes Cazzolla Gatti.
“Most species that appear in sampling are quite common, there are some rare and only a few unknown. If we take into account that there are many species that today have been able to observe a few times, it is likely that there is
Many more rare species that have not even been documented. ”

Their results, the authors ensure, highlight the vulnerability of global forest biodiversity to anthropogenic changes, in particular the use of soil and climate, since the survival of the rare taxa is the most threatened.
Know, underline, it is essential to protect.
Therefore, they have applied their model to the available databases – both on a continental level as a world-to estimate the number of unknown arboreal species and have identified the areas of the world in which they are more likely to be discovered, which would increase their
Possibilities of preservation.