The number of tree species on Earth.

[en] 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.

Disciplines :

Environmental sciences & ecology

Author, co-author :

Cazzolla Gatti, Roberto ; Department of Forestry and Natural Resources, Purdue University, West Lafayette, IN 47907 ; Department of Biological, Geological, and Environmental Sciences, Alma Mater Studiorum University of Bologna, Bologna 40126, Italy ; Biological Institute, Tomsk State University, Tomsk 634050, Russia

Reich, Peter B ; Department of Forest Resources, University of Minnesota, St. Paul, MN 55108, preich@umn.edu albeca.liang@gmail.com ; Institute for Global Change Biology and School for Environment and Sustainability, University of Michigan, Ann Arbor, MI 48109 ; Hawkesbury Institute for the Environment, Western Sydney University, Penrith 2753, Australia

Gamarra, Javier G P; Forestry Department, FAO, Rome 00153, Italy

Crowther, Tom; Institute of Integrative Biology, ETH Zurich 8092 Zurich, Switzerland

Hui, Cang ; Centre for Invasion Biology, Department of Mathematical Sciences, Stellenbosch University, Stellenbosch 7602, South Africa ; Mathematical Biology Unit, African Institute for Mathematical Sciences, Muizenberg 7945, South Africa

Morera, Albert ; Department of Crop and Forest Sciences, University of Lleida 25198 Lleida, Spain ; Joint Research Unit CTFC-AGROTECNIO-CERCA 25280 Solsona, Spain

Bastin, Jean-François ; Université de Liège - ULiège > TERRA Research Centre

de-Miguel, Sergio ; Department of Crop and Forest Sciences, University of Lleida 25198 Lleida, Spain ; Joint Research Unit CTFC-AGROTECNIO-CERCA 25280 Solsona, Spain

Nabuurs, Gert-Jan; Forest Ecology and Forest Management Group, Wageningen University and Research, Wageningen 6700 AA, The Netherlands

Svenning, Jens-Christian ; Center for Biodiversity Dynamics in a Changing World (BIOCHANGE), Department of Biology, Aarhus University DK-8000 Aarhus C, Denmark ; Section for Ecoinformatics and Biodiversity, Department of Biology, Aarhus University DK-8000 Aarhus C, Denmark

More authors (138 more)

Language :

English

Title :

The number of tree species on Earth.

Publication date :

08 February 2022

Journal title :

Proceedings of the National Academy of Sciences of the United States of America

ISSN :

0027-8424

eISSN :

1091-6490

Publisher :

National Academy of Sciences, United States

Volume :

119

Issue :

Pages :

e2115329119

Peer reviewed :

Peer Reviewed verified by ORBi

Additional URL :

https://syndication.highwire.org/content/doi/10.1073/pnas.2115329119

Available on ORBi :

since 21 February 2022

Statistics

Number of views

72 (8 by ULiège)

Number of downloads

78 (0 by ULiège)

More statistics

Scopus citations^®

Scopus citations^®
without self-citations

OpenCitations

Bibliography

R. M. May, Conceptual aspects of the quantification of the extent of biological diversity. Philos. Trans. R. Soc. Lond. B Biol. Sci. 345, 13-20 (1994).
R. Cazzolla Gatti, A century of biodiversity: Some open questions and some answers. Biodiversity 18, 175-185 (2017).
E. Beech, M. Rivers, S. Oldfield, P. P. Smith, Global Tree Search: The first complete global database of tree species and country distributions. J. Sustain. For. 36, 454-489 (2017).
H. Qian, T. Deng, H. Sun, Global and regional tree species diversity. J. Plant Ecol. 12, 210-215 (2018).
K. J. Gaston, Global patterns in biodiversity. Nature 405, 220-227 (2000).
P. Crane, Can we save the charismatic megaflora? Oryx 49, 377-378 (2015).
E.-D. Schulze, “The carbon and nitrogen cycle in forest ecosystems” in Carbon and Nitrogen Cycling in European Forest Ecosystems, E.-D. Schulze, Ed. (Ecological Studies [Analysis and Synthesis], Springer, Berlin, 2000), vol. 142, pp. 3-13.
A. R. Townsend, G. P. Asner, C. C. Cleveland, The biogeochemical heterogeneity of tropical forests. Trends Ecol. Evol. 23, 424-431 (2008).
J. Liang et al., Positive biodiversity-productivity relationship predominant in global forests. Science 354, aaf8957 (2016).
P. Balvanera et al., Quantifying the evidence for biodiversity effects on ecosystem functioning and services. Ecol. Lett. 9, 1146-1156 (2006).
B. A. Hawkins, M. Rodrıguez, S. G. Weller, Global angiosperm family richness revisited: Linking ecology and evolution to climate. J. Biogeogr. 38, 1253-1266 (2011).
S. P. Hubbell et al., Colloquium paper: How many tree species are there in the Amazon and how many of them will go extinct? Proc. Natl. Acad. Sci. U.S.A. 105 (suppl. 1), 11498-11504 (2008).
B. J. Cardinale et al., Biodiversity loss and its impact on humanity. Nature 486, 59-67 (2012).
G. C. Stevens, The latitudinal gradient in geographical range: How so many species coexist in the tropics. Am. Nat. 133, 240-256 (1989).
Z. Wang, J. H. Brown, Z. Tang, J. Fang, Temperature dependence, spatial scale, and tree species diversity in eastern Asia and North America. Proc. Natl. Acad. Sci. U.S.A. 106, 13388-13392 (2009).
B. J. Enquist et al., The commonness of rarity: Global and future distribution of rarity across land plants. Sci. Adv. 5, eaaz0414 (2019).
H. ter Steege et al., Hyperdominance in the Amazonian tree flora. Science 342, 1243092 (2013).
R. P. Leitão et al., Rare species contribute disproportionately to the functional structure of species assemblages. Proc. Biol. Sci. 283, 20160084 (2016).
L. E. Dee et al., When do ecosystem services depend on rare species? Trends Ecol. Evol. 34, 746-758 (2019).
S. Fauset et al., Hyperdominance in Amazonian forest carbon cycling. Nat. Commun. 6, 6857 (2015).
J. F. Bastin et al., The extent of forest in dryland biomes. Science 356, 635-638 (2017).
A. D. Barnosky et al., Has the Earth's sixth mass extinction already arrived? Nature 471, 51-57 (2011).
T. M. Brooks et al., Global biodiversity conservation priorities. Science 313, 58-61 (2006).
D. Cardoso et al., Amazon plant diversity revealed by a taxonomically verified species list. Proc. Natl. Acad. Sci. U.S.A. 114, 10695-10700 (2017).
B. R. Scheffers, L. N. Joppa, S. L. Pimm, W. F. Laurance, What we know and don't know about Earth's missing biodiversity. Trends Ecol. Evol. 27, 501-510 (2012).
J. M. Serra-Diaz, B. J. Enquist, B. Maitner, C. Merow, J. C. Svenning, Big data of tree species distributions: How big and how good? For. Ecosyst. 4, 30 (2017).
A. Chao, Nonparametric estimation of the number of classes in a population. Scand. J. Stat. 11, 265-270 (1984).
C. H. Chiu, A. Chao, Estimating and comparing microbial diversity in the presence of sequencing errors. PeerJ 4, e1634 (2016).
A. Chao, Estimating the population size for capture-recapture data with unequal catchability. Biometrics 43, 783-791 (1987).
S. Oldfield, C. Lusty, A. MacKinven, The World List of Threatened Trees (World Conservation Press, Cambridge, United Kingdom, 1998).
N. J. Gotelli, R. K. Colwell, “Estimating species richness” in Biological Diversity: Frontiers in Measurement and Assessment, A. E. Magurran, B. J. McGill, Eds. (Oxford University Press, Oxford, United Kingdom, 2011), pp. 39-54.
K. J. Iknayan, M. W. Tingley, B. J. Furnas, S. R. Beissinger, Detecting diversity: Emerging methods to estimate species diversity. Trends Ecol. Evol. 29, 97-106 (2014).
A. Chao, R. K. Colwell, C. W. Lin, N. J. Gotelli, Sufficient sampling for asymptotic minimum species richness estimators. Ecology 90, 1125-1133 (2009).
H. Ter Steege et al., The discovery of the Amazonian tree flora with an updated checklist of all known tree taxa. Sci. Rep. 6, 29549 (2016).
H. Ter Steege et al., Towards a dynamic list of Amazonian tree species. Sci. Rep. 9, 3501 (2019).
J. W. Slik et al., An estimate of the number of tropical tree species. Proc. Natl. Acad. Sci. U.S.A. 112, 7472-7477 (2015). Correction in: Proc. Natl. Acad. Sci. U.S.A. 112, E4628-E4629 (2015).
H. Ter Steege et al., Biased-corrected richness estimates for the Amazonian tree flora. Sci. Rep. 10, 10130 (2020).
A. Chao, L. Jost, Coverage-based rarefaction and extrapolation: Standardizing samples by completeness rather than size. Ecology 93, 2533-2547 (2012).
N. C. Pitman, P. M. Jørgensen, R. S. Williams, S. Leon-Yanez, R. Valencia, Extinction-rate estimates for a modern neotropical flora. Conserv. Biol. 16, 1427-1431 (2002).
O. R. Wearn, D. C. Reuman, R. M. Ewers, Extinction debt and windows of conservation opportunity in the Brazilian Amazon. Science 337, 228-232 (2012).
S. Chamberlain, K. Ram, V. Barve, D. Mcglinn, rgbif: Interface to the Global “Biodiversity” Information Facility “API” (R Package Version 0.9.8, 2016). https://cran.r-project.org/web/packages/rgbif/index.html. Accessed 15 March 2020.
B. S. Maitner et al., The bien r package: A tool to access the Botanical Information and Ecology Network (BIEN) database. Methods Ecol. Evol. 9, 373-379 (2018).
K. Banda-R et al.; DRYFLOR, Plant diversity patterns in neotropical dry forests and their conservation implications. Science 353, 1383-1387 (2016).
G. Dauby et al., RAINBIO: A mega-database of tropical African vascular plants distributions. PhytoKeys 74, 1-18 (2016).
P. Flemons, B. Raymond, P. Brenton, L. Belbin, Atlas of living Australia. https://www.ala.org.au/. Accessed 12 February 2019.
BGCI, GlobalTreeSearch online database. https://www.bgci.org/global_tree_search. php. Accessed 19 June 2017.
B. Boyle et al., The taxonomic name resolution service: An online tool for automated standardization of plant names. BMC Bioinformatics 14, 16 (2013).
A. Chao et al., Quantifying sample completeness and comparing diversities among assemblages. Ecol. Res. 35, 292-314 (2020).
A. Chao, S. M. Lee, Estimating the number of classes via sample coverage. J. Am. Stat. Assoc. 87, 210-217 (1992).
C. H. Chiu, Y. T. Wang, B. A. Walther, A. Chao, An improved nonparametric lower bound of species richness via a modified good-turing frequency formula. Biometrics 70, 671-682 (2014).
J. P. Mellard, P. Audoye, M. Loreau, Seasonal patterns in species diversity across biomes. Ecology 100, e02627 (2019).
T. F. Allen, T. W. Hoekstra, The confusion between scale-defined levels and conventional levels of organization in ecology. J. Veg. Sci. 1, 5-12 (1990).
N. J. Gotelli, R. K. Colwell, Quantifying biodiversity: Procedures and pitfalls in the measurement and comparison of species richness. Ecol. Lett. 4, 379-391 (2001).
A. E. Magurran, Measuring Biological Diversity (Blackwell Science, Oxford, United Kingdom, 2004).
K. Mao et al., Distribution of living Cupressaceae reflects the breakup of Pangea. Proc. Natl. Acad. Sci. U.S.A. 109, 7793-7798 (2012).
K. Mao, G. Hao, J. Liu, R. P. Adams, R. I. Milne, Diversification and biogeography of Juniperus (Cupressaceae): Variable diversification rates and multiple intercontinental dispersals. New Phytol. 188, 254-272 (2010).
J. H. Whiteside, D. S. Grogan, P. E. Olsen, D. V. Kent, Climatically driven biogeographic provinces of Late Triassic tropical Pangea. Proc. Natl. Acad. Sci. U.S.A. 108, 8972-8977 (2011).
M. D. Crisp, L. G. Cook, Cenozoic extinctions account for the low diversity of extant gymnosperms compared with angiosperms. New Phytol. 192, 997-1009 (2011).
A. E. Magurran, Ecological Diversity and Its Measurement (Princeton University Press, Princeton, NJ, 1988).
T. W. Crowther et al., Mapping tree density at a global scale. Nature 525, 201-205 (2015).
R. A. Fisher, A. S. Corbet, C. B. Williams, The relation between the number of species and the number of individuals in a random sample of an animal population. J. Anim. Ecol. 12, 42-58 (1943).
S. P. Hubbell, Estimating the global number of tropical tree species, and Fisher's paradox. Proc. Natl. Acad. Sci. U.S.A. 112, 7343-7344 (2015).
I. Volkov, J. R. Banavar, S. P. Hubbell, A. Maritan, Patterns of relative species abundance in rainforests and coral reefs. Nature 450, 45-49 (2007).
R. K. Colwell, J. A. Coddington, Estimating terrestrial biodiversity through extrapolation. Philos. Trans. R. Soc. Lond. B Biol. Sci. 345, 101-118 (1994).
B. A. Walther, S. Morand, Comparative performance of species richness estimation methods. Parasitology 116, 395-405 (1998).
A. Chao, R. K. Colwell, Thirty years of progeny from Chao's inequality: Estimating and comparing richness with incidence data and incomplete sampling. SORT Stat. Oper. Res. Trans. 41, 3-54 (2017).
T. C. Hsieh, K. H. Ma, A. Chao, iNEXT: Interpolation and Extrapolation for Species Diversity (R Package Version 2.0.20, 2020). http://chao.stat.nthu.edu.tw/wordpress/software_download/. Accessed 15 March 2020.
U. Brose, N. D. Martinez, R. J. Williams, Estimating species richness: Sensitivity to sample coverage and insensitivity to spatial patterns. Ecology 84, 2364-2377 (2003).
H. Wagner, O. Wildi, Realistic simulation of the effects of abundance distribution and spatial heterogeneity on non-parametric estimators of species richness. Eco-science 9, 241-250 (2002).
W. E. Kunin et al., Upscaling biodiversity: Estimating the species-area relationship from small samples. Ecol. Monogr. 88, 170-187 (2018).
H. Xu et al., Assessing non-parametric and area-based methods for estimating regional species richness. J. Veg. Sci. 23, 1006-1012 (2012).
H. Chen, P. C. Boutros, VennDiagram: A package for the generation of highly-customizable Venn and Euler diagrams in R. BMC Bioinformatics 12, 35 (2011).