More than 100 researchers from around the world conducted a study to estimate the number of tree species on Earth. They have developed the largest database and estimated the existence of 73,274 tree species, of which several thousand are yet to be discovered.
“We combined individual datasets into one massive global dataset of tree-level data,” says quantitative forest ecologist Jingjing Liang of Purdue University.
“Each set comes from someone going out to a forest stand and measuring every single tree – collecting information about the tree species, sizes, and other characteristics. Counting the number of tree species worldwide is like a puzzle with pieces spread all over the world. It is very possible we could lose undiscovered tree species to extinction before we even find them,” Jingjing Liang added.
The report combined two vast tree datasets – one belonging to the Global Forest Biodiversity Initiative, of which Liang is the coordinator, and another database called TreeChange. The data-pooling project, combining many years’ worth of ground-source tree cataloguing, compiled a global occurrence dataset of tree species across a grid of over nine thousand 100 × 100-kilometre (62 x 62-mile) cells on the planet.
With statistical adjustments accounting for the comparative richness of biomes in different regions, the researchers concluded that there are likely about 9,200 tree species yet to be discovered, although they acknowledged this to be an estimate based on incomplete data, including areas where the mapping and analysis of tree species are limited.
A third of the world’s species qualified as rare
In addition, almost a third of the world’s species are qualified by scientists as rare, with a low population and found in limited regions. These species are, thus, more vulnerable to the threat of extinction. Only 0.1% of the species are present on the five continents. South America has the highest proportion (49%) of endemic species, i.e. only present on this continent.
“These findings underscore the vulnerability of tree species diversity globally,” wrote the study authors, particularly in the face of “anthropogenic land use and future climate.” “Losing areas of forest containing these rare species will have a direct and potentially long-term impact on global species diversity, and their contribution to ecosystem services,” they added.