More than 9000 tree species are still waiting to be discovered. This is the result of a new global inventory presented by Peter Reich from the University of Michigan and his team in »PNAS«. This would mean that their diversity would be 14 percent greater than previously thought. The total number of all tree species would then be around 73,000 instead of the previously known 60,065.
For the inventory, the working group combined the data sets of the Global Forest Biodiversity Initiative and TREECHANGE, which collect characteristic values of tree surveys in defined spatial units. Each individual tree is identified and measured. This merger alone increased the diversity to 64,000 known tree species. With the help of newly developed statistical models, Reich and Co then calculated how many unique species can occur in a biome, such as rainforests, savannas or boreal coniferous forests.
The total number determined is even a conservative estimate, the researchers write. They suspect 40 percent of these unknown species to be in South America, primarily in the Andes and Amazonia. The continent already has the highest tree diversity and endemism rate; at the same time, it is also home to an above-average number of rarities. “That’s why the preservation of forests in South America has top priority, especially in view of the current crisis in tropical forests, which is due to human influences such as deforestation, fires and climate change,” says Reich.
Around the world, around half to two-thirds of all known tree species occur in tropical and subtropical moist forests, which are species-rich but at the same time poorly researched by scientists. Tropical and subtropical dry forests are also likely to have a large number of undiscovered tree species.