Knowledge of a species’ abundance is critically important for assessing its risk of extinction, but for the vast majority of wild animal and plant species such data are scarce at biogeographic scales. Here, we estimate the total number of reef-building corals and the population sizes of more than 300 individual species on reefs spanning the Pacific Ocean biodiversity gradient, from Indonesia to French Polynesia. Our analysis suggests that approximately half a trillion corals (0.3 × 1012–0.8 × 1012) inhabit these coral reefs, similar to the number of trees in the Amazon. Two-thirds of the examined species have population sizes exceeding 100 million colonies, and one-fifth of the species even have population sizes greater than 1 billion colonies. Our findings suggest that, while local depletions pose imminent threats that can have ecologically devastating impacts to coral reefs, the global extinction risk of most coral species is lower than previously estimated.
This is a preview of subscription content, access via your institution
Open Access articles citing this article.
Landscape Ecology Open Access 29 June 2022
Nature Communications Open Access 03 May 2022
Subscribe to Nature+
Get immediate online access to the entire Nature family of 50+ journals
Subscribe to Journal
Get full journal access for 1 year
only $9.92 per issue
All prices are NET prices.
VAT will be added later in the checkout.
Tax calculation will be finalised during checkout.
Get time limited or full article access on ReadCube.
All prices are NET prices.
Wilkinson, C. Status of Coral Reefs of the World: 2008 (Global Coral Reef Monitoring Network and Reef and Rainforest Research Centre, 2008).
Jackson, J. B. C., Donovan, M. K., Cramer, K. L. & Lam, V. V. Status and Trends of Caribbean Coral Reefs: 1970–2012 (Global Coral Reef Monitoring Network, 2014).
Eakin, C. M. et al. Caribbean corals in crisis: record thermal stress, bleaching, and mortality in 2005. PLoS ONE 5, e13969 (2010).
Baker, A. C., Glynn, P. W. & Riegl, B. Climate change and coral reef bleaching: an ecological assessment of long-term impacts, recovery trends and future outlook. Estuar. Coast. Shelf Sci. 80, 435–471 (2008).
Hughes, T. P. et al. Global warming transforms coral reef assemblages. Nature 556, 492–496 (2018).
Hughes, T. P. et al. Spatial and temporal patterns of mass bleaching of corals in the Anthropocene. Science 359, 80–83 (2018).
De’ath, G., Fabricius, K. E., Sweatman, H. & Puotinen, M. The 27-year decline of coral cover on the Great Barrier Reef and its causes. Proc. Natl Acad. Sci. USA 109, 17995–17999 (2012).
Gardner, T. A. Long-term region-wide declines in Caribbean corals. Science 301, 958–960 (2003).
Carpenter, K. E. et al. One-third of reef-building corals face elevated extinction risk from climate change and local impacts. Science 321, 560–563 (2008).
ter Steege, H. et al. Estimating the global conservation status of more than 15,000 Amazonian tree species. Sci. Adv. 1, e1500936 (2015).
Fauset, S. et al. Hyperdominance in Amazonian forest carbon cycling. Nat. Commun. 6, 6857 (2015).
Crowther, T. W. et al. Mapping tree density at a global scale. Nature 525, 201–205 (2015).
Connell, J., Hughes, T. & Wallace, C. A 30-year study of coral abundance, recruitment, and disturbance at several scales in space and time. Ecol. Monogr. 67, 461–488 (1997).
Hughes, T. P. & Jackson, J. B. C. Population dynamics and life histories of foliaceous corals. Ecol. Monogr. 55, 141–166 (1985).
ter Steege, H. et al. Hyperdominance in the Amazonian tree flora. Science 342, 1243092 (2013).
Gaston, K. J. & Blackburn, T. M. How many birds are there? Biodivers. Conserv. 6, 615–625 (1997).
Kerry, J. T. & Bellwood, D. R. Do tabular corals constitute keystone structures for fishes on coral reefs? Coral Reefs 34, 41–50 (2015).
Connolly, S. R., Hughes, T. P., Bellwood, D. R. & Karlson, R. H. Community structure of corals and reef fishes at multiple scales. Science 309, 1363–1365 (2005).
Connolly, S. R., Hughes, T. P. & Bellwood, D. R. A unified model explains commonness and rarity on coral reefs. Ecol. Lett. 20, 477–486 (2017).
Hubbell, S. P. Estimating the global number of tropical tree species, and Fisher’s paradox. Proc. Natl Acad. Sci. USA 112, 7343–7344 (2015).
Hughes, T. P., Bellwood, D. R. & Connolly, S. R. Biodiversity hotspots, centres of endemicity, and the conservation of coral reefs. Ecol. Lett. 5, 775–784 (2002).
Hughes, T. P., Bellwood, D. R., Connolly, S. R. & Cornell, H. V. Double jeopardy and global extinction risk in corals and reef fishes. Curr. Biol. 24, 2946–2951 (2014).
Kinlan, B. P. & Gaines, S. D. Propagule dispersal in marine and terrestrial environments: a community perspective. Ecology 84, 2007–2020 (2003).
Hull, P. M., Darroch, S. A. F. & Erwin, D. H. Rarity in mass extinctions and the future of ecosystems. Nature 528, 345–351 (2015).
Cardoso, P., Borges, P. A. V., Triantis, K. A., Ferrández, M. A. & Martín, J. L. Adapting the IUCN Red List criteria for invertebrates. Biol. Conserv. 144, 2432–2440 (2011).
Cardoso, P., Borges, P. A. V., Triantis, K. A., Ferrández, M. A. & Martín, J. L. The underrepresentation and misrepresentation of invertebrates in the IUCN Red List. Biol. Conserv. 149, 147–148 (2012).
Estes, J. A., Duggins, D. O. & Rathbun, G. B. The ecology of extinctions in kelp forest communities. Conserv. Biol. 3, 252–264 (1989).
Oliver, J. & Babcock, R. Aspects of the fertilization ecology of broadcast spawning corals: sperm dilution effects and in situ measurements of fertilization. Biol. Bull. 183, 409–417 (1992).
Knowlton, N., Lang, J. C. & Keller, B. D. Case study of natural population collapse: post-hurricane predation on Jamaican staghorn corals. Smithson. Contrib. Mar. Sci. 31, 1–25 (1990).
Gaston, K. J. & Fuller, R. A. Commonness, population depletion and conservation biology. Trends Ecol. Evol. 23, 14–19 (2008).
Säterberg, T., Sellman, S. & Ebenman, B. High frequency of functional extinctions in ecological networks. Nature 499, 468–470 (2013).
Pratchett, M. S. Dietary overlap among coral-feeding butterflyfishes (Chaetodontidae) at Lizard Island, northern Great Barrier Reef. Mar. Biol. 148, 373–382 (2005).
Huang, D., Licuanan, W. Y., Baird, A. H. & Fukami, H. Cleaning up the ‘Bigmessidae’: molecular phylogeny of scleractinian corals from Faviidae, Merulinidae, Pectiniidae and Trachyphylliidae. BMC Evol. Biol. 11, 37 (2011).
Knowlton, N. & Jackson, J. B. C. New taxonomy and niche partitioning on coral reefs: jack of all trades or master of some? Trends Ecol. Evol. 9, 7–9 (1994).
Gilpin, M. E. & Soulé, M. E. in Conservation Biology: The Science of Scarcity and Diversity (ed, Soulé, M. E.) 19–34 (Sinauer Associates, 1986).
Bak, R. P. M. & Meesters, E. H. Population structure as a response of coral communities to global change. Am. Zool. 39, 56–65 (1999).
McClanahan, T. R., Ateweberhan, M. & Omukoto, J. Long-term changes in coral colony size distributions on Kenyan reefs under different management regimes and across the 1998 bleaching event. Mar. Biol. 153, 755–768 (2008).
Riegl, B. M., Bruckner, A. W., Rowlands, G. P., Purkis, S. J. & Renaud, P. Red Sea coral reef trajectories over 2 decades suggest increasing community homogenization and decline in coral size. PLoS ONE 7, e38396 (2012).
Hughes, T. P. et al. Coral reefs in the Anthropocene. Nature 546, 82–90 (2017).
Global Distribution of Coral Reefs (UNEP-WCMC, WorldFish Centre, WRI & TNC, 2018); https://data.unep-wcmc.org/datasets/
Bruno, J. F. & Valdivia, A. Coral reef degradation is not correlated with local human population density. Sci. Rep. 6, 29778 (2016).
Bruno, J. Data from: Coral reef degradation is not correlated with local human population density. Dryad Digital Repository https://doi.org/10.5061/dryad.48r68 (2016).
Karlson, R. H., Cornell, H. V. & Hughes, T. P. Coral communities are regionally enriched along an oceanic biodiversity gradient. Nature 429, 867–870 (2004).
Cornell, H. V., Karlson, R. H. & Hughes, T. P. Scale-dependent variation in coral community similarity across sites, islands, and island groups. Ecology 88, 1707–1715 (2007).
Cornell, H. V., Karlson, R. H. & Hughes, T. P. Local-regional species richness relationships are linear at very small to large scales in west-central Pacific corals. Coral Reefs 27, 145–151 (2008).
Connolly, S. R., Dornelas, M., Bellwood, D. R. & Hughes, T. P. Testing species abundance models: a new bootstrap approach applied to Indo-Pacific coral reefs. Ecology 90, 3138–3149 (2009).
Reef Habitat Maps (NOAA-NCCOS, accessed 10 November 2017); https://products.coastalscience.noaa.gov/collections/benthic/default.aspx
Purkis, S. J. et al. High-resolution habitat and bathymetry maps for 65,000 sq. km of Earth’s remotest coral reefs. Coral Reefs 38, 467–488 (2019).
Roelfsema, C., Phinn, S., Jupiter, S., Comley, J. & Albert, S. Mapping coral reefs at reef to reef-system scales, 10s–1000s km2, using object-based image analysis. Int. J. Remote Sens. 34, 6367–6388 (2013).
Bürkner, P.-C. brms: an R package for Bayesian multilevel models using Stan. J. Stat. Softw. 80, 1–28 (2017).
Warton, D. I. & Hui, F. K. C. The arcsine is asinine: the analysis of proportions in ecology. Ecology 92, 3–10 (2011).
Marsh, L. M., Bradbury, R. H. & Reichelt, R. E. Determination of the physical parameters of coral distributions using line transect data. Coral Reefs 2, 175–180 (1984).
Hughes, T. P. Population dynamics based on individual size rather than age: a general model with a reef coral example. Am. Nat. 123, 778–795 (1984).
Hall, V. R. & Hughes, T. P. Reproductive strategies of modular organisms: comparative studies of reef-building corals. Ecology 77, 950–963 (1996).
Hughes, T. P., Connolly, S. R. & Keith, S. A. Geographic ranges of reef corals (Cnidaria: Anthozoa: Scleractinia) in the Indo-Pacific. Ecology 94, 1659 (2013).
Bar-On, Y. M., Phillips, R. & Milo, R. The biomass distribution on Earth. Proc. Natl Acad. Sci. USA 115, 6506–6511 (2018).
van den Hoogen, J. et al. Soil nematode abundance and functional group composition at a global scale. Nature 572, 194–198 (2019).
Hubbell, S. P. et al. How many tree species are there in the Amazon and how many of them will go extinct? Proc. Natl Acad. Sci. USA 105, 11498–11504 (2008).
Atkinson, A., Siegel, V., Pakhomov, E. A., Jessopp, M. J. & Loeb, V. A re-appraisal of the total biomass and annual production of Antarctic krill. Deep-Sea Res. I 56, 727–740 (2009).
Current World Population (Worldometer, accessed 13 May 2020); https://www.worldometers.info/world-population/
California Condor Recovery Program: 2017 Annual Population Status (US Fish and Wildlife Service, 2017).
Goodrich, J. M. et al. Panthera tigris. The IUCN Red List of Threatened Species 2015 Report number e.T15955A50659951 (IUCN, 2015).
We thank many individuals for assistance with species identification and field surveys, particularly A. Baird, S. Blake, M. Boyle, H. Cornell, E. Dinsdale, R. Karlson, M. Kaspartov, P. Osmond and J. Wolstenholme. Major funding for this analysis was provided by the Australian Research Council’s Centre of Excellence Program (CE140100020) and a Laureate Fellowship to T.P.H. (FL120100063).
The authors declare no competing interests.
Peer review information Nature Ecology & Evolution thanks Hans ter Steege, Robert Steneck and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.
Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Supplementary Tables 1–2 and Figs. 1–7.
Supplementary Data 1: a table listing the abundance of 318 Indo-Pacific coral species by region and habitat type measured as number of intercepts. Supplementary Data 2: a table listing the estimated population sizes of 318 Indo-Pacific coral species and their current IUCN conservation status. Supplementary Data 3: a table listing the locations and sources of 61 compiled reef habitat maps.
About this article
Cite this article
Dietzel, A., Bode, M., Connolly, S.R. et al. The population sizes and global extinction risk of reef-building coral species at biogeographic scales. Nat Ecol Evol 5, 663–669 (2021). https://doi.org/10.1038/s41559-021-01393-4
This article is cited by
Nature Ecology & Evolution (2022)
Nature Communications (2022)
Nature Ecology & Evolution (2022)
Landscape Ecology (2022)
Specific Detection of Coral-Associated Ruegeria, a Potential Probiotic Bacterium, in Corals and Subtropical Seawater
Marine Biotechnology (2021)