One would assume that, by now, most tree species on our planet would have been mapped. However, the total number of tree species remains uncertain due to tremendous financial, taxonomic, and logistical difficulties. Incidentally, researchers concluded that there are still thousands of rare, undiscovered species. They published their findings in the science journal PNAS.
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tensive knowledge about tree diversity is valuable as they are vital for our planet. Forests provide numerous "ecosystem services" to humanity free of charge. They help clean the air, filter our water, act as a buffer for extreme weather, provide food and shelter to a wide variety of animals, and slow global warming by absorbing carbon dioxide as they grow.
Thousands of undiscovered tree species
Over a hundred scientists collaborated on this study for several years. Combining several datasets, the team created the most extensive forest database in the world. New statistical methods were used on this database to calculate the total number of unique tree species at three different scales (biome, continental and global). The resulting estimation also comprised species that have yet to be discovered and characterized by biologists.
The team calculated that there must be a total of approximately 73.000 tree species on Earth; among them, about 9200 tree species are (as of yet) undiscovered. The researchers expect almost half of these undiscovered tree species to be located in South America.
Biome-level tree species richness estimation. This map shows the number of tree species calculated in terrestrial biomes of each continent as a color gradient from low richness (yellow) to high richness (red). - Image Credit: Cazzolla Gatti et al. via PNAS
Why are there so many undiscovered tree species?
As we have established, the actual number of tree species on our planet is estimated to be significantly higher than previously believed. So how is it that we did not know about their existence before?
According to the scientists, this is because most of the (as of yet) undiscovered tree species are probably located in remote areas. The team suspects that most of them grow in sparsely populated subtropical and tropical forests with very few visiting scientists. Examples of such areas would be parts of Central Africa, remote forests in Southeast Asia, and rainforests such as the Amazon. In addition, there are probably many tree species waiting to be discovered on remote, uninhabited islands.
The study reveals that the majority of undiscovered tree species are likely to be rare, with sparse populations and limited spatial distribution. That makes the undiscovered species particularly vulnerable to human-caused disturbances like climate change and deforestation. The new findings will help prioritize forest conservation efforts.
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Protecting our forests
According to Peter Reich, one of the study's authors, the results emphasize how vulnerable worldwide forest biodiversity is to anthropogenic transformations, especially climate and land use, as the survival of rare populations is disproportionately endangered by these types of pressure.
The researchers highlight that it is crucial to scientifically describe the undiscovered species, protect our forest, and save the undiscovered species from extinction.
Sources and further reading:
Why don't evergreens change color and drop their leaves every fall? (Universal-Sci)
Where the old things are: Australia's most ancient trees (Universal-Sci)
High-value opportunities exist to restore tropical rainforests around the world – here's how we mapped them (Universal-Sci)
Urban greening can save species, cool warming cities, and make us happy (Universal-Sci)
Cool Tech: Internet of Trees maps the health of trees online (Universal-Sci)
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