Trees that still hide a forest? According to a study published on Monday, researchers have estimated that the number of tree species on Earth is significantly higher than currently known.
Some 64,100 tree species have already been listed. But according to their work, published in the journal of the national academy of sciences of the united states (pnas) and whose estimates are based on a more complete database and a more advanced statistical method than before, the total number of species would be around 73,300, or 14% more. This means that approximately 9,200 species have yet to be discovered.
Nearly a third of the species qualified as rare
Overall, about 43% of all species are found in South America, followed by Eurasia (22%), Africa (16%), then North America (15%) and Oceania (11%), according to the study. Half to two-thirds of all known species are found in tropical or subtropical rainforests on five continents, researchers estimate. A large proportion of the species still to be identified should thus be found in these regions, where fewer surveys are carried out.
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.
These results highlight the vulnerability of tree species diversity worldwide
Only 0.1% of the species are present on the five continents. South America has the highest proportion (49%) of endemic species, ie only present on this continent. “These findings underscore the vulnerability of tree species diversity globally,” write 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.
Species surveys are very long-term work and present many challenges, in particular access to certain regions or even identification consistency, as several botanists can, for example, characterize the same species slightly differently.