Trillions of trees are growing on Earth, though how many kinds there are has been underestimated, a new study finds.
Earth hosts roughly 64,100 known tree species. But there could be at least 73,300 - about 14 percent more than previously thought — a global collaboration of researchers reports in the Feb. 8 Proceedings of the National Academy of Sciences.
More than a third of the 9,200 undiscovered species are probably rare and hiding out in South America’s biodiversity hot spots, such as the Amazon and tropical Andes, biologist Roberto Cazzolla Gatti of the University of Bologna in Italy and colleagues say. To estimate the number of Earth’s existing tree species, the team analyzed global forest data from two databases — the Global Forest Biodiversity Initiative and TREECHANGE. The researchers used a statistical analysis to account for the number of rare, infrequent trees that could be overlooked, revealing the new difference between documented species and novel ones.
If more than 9,000 types of stationary, comparatively massive trees remain undetected, Cazzolla Gatti says, then the number of much smaller and more mobile animal species that are still unknown must be even greater
Of the 73,300 estimated species, the researchers predict there are 9,200 that are yet to be discovered.
But most rare species are in tropical forests, fast disappearing because of climate change and deforestation.
The study is based on a database of tens of millions of trees in more than 100,000 forest plots around the world.
The researchers used statistical techniques to predict the likely number of tree species, correcting for gaps in existing data.
The findings suggest more must be done to protect the incredible life forms needed for food, timber and medicine and to fight climate change by sucking carbon dioxide from the air.
Lead researcher Dr Peter Reich, of the University of Minnesota in St Paul, said the findings highlighted the vulnerability of global forest biodiversity.
"Our data will help us assess where biodiversity is the most threatened," he told BBC News.
One of the most fundamental questions in ecology is how many species inhabit the Earth. However, due to massive logistical and financial challenges and taxonomic difficulties connected to the species concept definition, the global numbers of species, including those of important and well-studied life forms such as trees, still remain largely unknown. Here, based on global ground-sourced data, we estimate the total tree species richness at global, continental, and biome levels. Our results indicate that there are ∼73,000 tree species globally, among which ∼9,000 tree species are yet to be discovered. Roughly 40% of undiscovered tree species are in South America. Moreover, almost one-third of all tree species to be discovered may be rare, with very low populations and limited spatial distribution (likely in remote tropical lowlands and mountains). These findings highlight the vulnerability of global forest biodiversity to anthropogenic changes in land use and climate, which disproportionately threaten rare species and thus, global tree richness.
The research could help scientists target conservation efforts amid accelerating biodiversity loss worldwide (SN: 4/22/20). In vulnerable places such as the Amazon, where deforestation and fires are quickly erasing habitat, many plants and animals could be being wiped off the map before they are ever documented (SN: 9/1/21).
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