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Research article - Peer-reviewed, 2022

The number of tree species on Earth

Gatti, Roberto Cazzolla; Reich, Peter B.; Gamarra, Javier G. P.; Crowther, Tom; Hui, Cang; Morera, Albert; Bastin, Jean-Francois; de-Miguel, Sergio; Nabuurs, Gert-Jan; Svenning, Jens-Christian; Serra-Diaz, Josep M.; Merow, Cory; Enquist, Brian; Kamenetsky, Maria; Lee, Junho; Zhu, Jun; Fang, Jinyun; Jacobs, Douglass F.; Pijanowski, Bryan; Banerjee, Arindam;
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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 groundsourced 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.


biodiversity; forests; hyperdominance; rarity; richness

Published in

Proceedings of the National Academy of Sciences of the United States of America
2022, volume: 119, number: 6, article number: e2115329119

Authors' information

Gatti, Roberto Cazzolla
Purdue University
Gatti, Roberto Cazzolla
Tomsk State University
Gatti, Roberto Cazzolla
University of Bologna
Reich, Peter B.
University of Michigan
Reich, Peter B.
Western Sydney University
Reich, Peter B.
University of Minnesota Twin Cities
Gamarra, Javier G. P.
Food and Agriculture Organization of the United Nations (FAO)
Crowther, Tom
Forest Research Institute
Crowther, Tom
ETH Zurich
Hui, Cang
Stellenbosch University
Morera, Albert
Morera, Albert
Universitat de Lleida
Bastin, Jean-Francois
University of Liege
de-Miguel, Sergio
de-Miguel, Sergio
Universitat de Lleida
Nabuurs, Gert-Jan
Wageningen University and Research
Svenning, Jens-Christian
Aarhus University
Serra-Diaz, Josep M.
Universite de Lorraine
Merow, Cory
University of Connecticut
Enquist, Brian
University of Arizona
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Sustainable Development Goals

SDG15 Life on land

UKÄ Subject classification

Forest Science

Publication Identifiers


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