Researchers have estimated that the number of tree species on Earth is higher than currently known, according to a study published Monday, January 31, with more than 9,000 species still to be discovered. “Estimating the number of tree species is essential for guiding, optimizing and prioritizing forest conservation efforts around the globe”underline these works (in English)published in the journal of the National Academy of Sciences of the United States (Pnas) and in which dozens of scientists participated.
Some 64,100 tree species have already been listed. But according to this work, 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.
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.
Moreover, 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. And almost a third of the world’s species are classified by scientists as rare, with low populations and found in limited regions. These species are thus more vulnerable to the threat of extinction.
“These findings highlight the vulnerability of tree species diversity around the world”write the authors of the study, particularly in the face of “anthropogenic land use and future climate”. Thereby, “losing areas of forest containing these rare species will have a direct and potentially long-term impact on global species diversity”. 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.