Earth may be home to 9,000 more species of trees than believed

BOLOGNA, Italy — Earth could be home to 9,000 more species of tree than previously believed, according to scientists. A third of these trees are rare species with a population that is limited in terms of numbers and the size of area they cover, a research team from around the world reports.

The first-ever estimate of the number of tree species in the world shows there are more 73,000 different types of tree in existence — 9,000 more than was previously thought. It took academics three years to count them all. In all, 150 scientists working with the Global Forest Biodiversity Initiative are behind the study.

Researchers say their findings highlight how fragile biodiversity is and how vulnerable it is to changes caused by humans, such as the climate crisis and unsustainable land use, with rare species being at the greatest risk. Better scientific expertise about the richness and diversity of trees found all over the world is key to preserving ecosystems, according to the academics.

“These results highlight the vulnerability of global forest biodiversity to anthropogenic changes, particularly land use and climate, because the survival of rare taxa is disproportionately threatened by these pressures,” says study co-author Peter Reich, of the University of Minnesota, in a statement.

The team collected an extensive database of forest tree species and then mapped them. This process identified around 40 million trees belonging to 64,000 species. Once this was done, the researchers used artificial intelligence and a supercomputer at an American lab to do complex calculations, which discovered there are in fact 73,000 tree species, 14 percent more than previously thought.

Before the research was conducted, scientists’ knowledge of trees in many parts of the world was patchy as data was only collected by observation or making lists of trees in different areas. Of the unknown species, 40 percent of them could be in grasslands and tropical forests in South America.

Around 3,000 of the once-unknown trees are rare and populate tropical or sub-tropical areas.

“Extensive knowledge of tree richness and diversity is key to preserving the stability and functionality of ecosystems,” says study first author Roberto Cazzolla Gatti, a professor with the University of Bologna’s Department of Biological, Geological and Environmental Sciences. “Until today, our data regarding wide areas of the planet was very limited and based on field-observation and lists of species covering different areas. These limitations were detrimental to a global perspective on the issue.

“To get a reliable estimate of biodiversity, we need to pay attention to the number of rare species that are currently known, those that were found one, two or three times during the sampling on the field,” he continues. “Indeed, most of the species are quite common and numerous, there are a few rare ones and even less are those that we don’t know. If many species have been observed only a few times, there will probably be many rare species that have not yet been documented.”

Adds study co-author Jingjing Liang, from Purdue University: “We combined individual datasets, coming from someone going out to a forest stand and measuring every single tree, into one massive global dataset of tree-level data. Counting the number of tree species worldwide is like a puzzle with pieces spreading all over the world. We, the Global Forest Biodiversity Initiative (GFBI), solved it together as a team, each sharing our own piece.”

The findings are published in the journal Proceedings of the National Academy of Sciences.

Report by South West News Service writer Gwyn Wright