posts: 54648
Data license: CC-BY
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| 54648 | How many species are there? | how-many-species-are-there | post | publish | <!-- wp:paragraph --> <p>How many species do we share our planet with? It's such a basic and fundamental question to understanding the world around us. </p> <!-- /wp:paragraph --> <!-- wp:paragraph --> <p>It's almost unthinkable that we would not know this number or at least have a good estimate. But the truth is that it's a question that continues to escape the world's taxonomists.</p> <!-- /wp:paragraph --> <!-- wp:paragraph --> <p>An important distinction is <strong>how many species we have identified and described</strong> and how many species there actually are. We've only identified a small fraction of the world's species, so these numbers are very different.</p> <!-- /wp:paragraph --> <!-- wp:heading {"level":3} --> <h3>How many species have we <em>described</em>?</h3> <!-- /wp:heading --> <!-- wp:columns --> <div class="wp-block-columns"><!-- wp:column --> <div class="wp-block-column"><!-- wp:paragraph --> <p>Before we look at estimates of how many species there are in total, we should first ask the question of how many species we <em>know that we know. </em>Species that we have identified and named.</p> <!-- /wp:paragraph --> <!-- wp:paragraph --> <p>The <a href="https://www.iucnredlist.org/resources/summary-statistics">IUCN Red List</a> tracks the number of described species and updates this figure annually based on the latest work of taxonomists. In 2021, it listed 2.13 million species on the planet. In the chart, we see the breakdown across a range of taxonomic groups – 1.05 million insects, over 11,000 birds, over 11,000 reptiles, and over 6,000 mammals.</p> <!-- /wp:paragraph --> <!-- wp:paragraph --> <p>These figures – particularly for lesser-known groups such as plants or fungi – might be a bit too high. This is because some described species are synonyms – the description of already-known species, simply given a separate name.{ref}Costello, M. J., May, R. M., & Stork, N. E. (2013). Can we name Earth's species before they go extinct?. Science, 339(6118), 413-416.{/ref} There is a continual evaluation process to remove synonyms (and most are removed eventually), but often species are added at a faster rate than synonyms can be found and removed.{ref}Solow, A. R., Mound, L. A., & Gaston, K. J. (1995). Estimating the rate of synonymy. Systematic Biology, 44(1), 93-96.{/ref} To give a sense of how large this effect might be, in a study published in Science, Costello et al. (2013) estimated that around 20% of the described species were undiscovered synonyms (in other words, duplicates).{ref}Costello, M. J., May, R. M., & Stork, N. E. (2013). Can we name Earth's species before they go extinct?. Science, 339(6118), 413-416.{/ref} They estimated that the 1.9 million described species at the time were actually closer to 1.5 million unique species.</p> <!-- /wp:paragraph --> <!-- wp:paragraph --> <p>If we were to assume this "20% synonym" figure held true, our 2.12 million described species might actually be closer to 1.7 million.</p> <!-- /wp:paragraph --> <!-- wp:paragraph --> <p>Regardless, we know that all these figures underestimate the actual number of species. The fact that there are so many species that we've yet to discover has real consequences for our ability to understand changes in global biodiversity and the rate of species extinctions. </p> <!-- /wp:paragraph --> <!-- wp:paragraph --> <p>If we don't know that certain species exist, we also don't know that they might have, or will soon, go extinct. Some species will inevitably go extinct before we realize that they used to exist.</p> <!-- /wp:paragraph --></div> <!-- /wp:column --> <!-- wp:column --> <div class="wp-block-column"><!-- wp:html --> <iframe src="https://ourworldindata.org/grapher/number-of-described-species?country=Fishes~Insects~Reptiles~Mammals~Birds~Amphibians~Corals~Molluscs~Crustaceans~Arachnids~All+groups~Fungi+and+Protists" loading="lazy" style="width: 100%; height: 600px; border: 0px none;"></iframe> <!-- /wp:html --></div> <!-- /wp:column --></div> <!-- /wp:columns --> <!-- wp:heading {"level":3} --> <h3>How many species are there really?</h3> <!-- /wp:heading --> <!-- wp:columns --> <div class="wp-block-columns"><!-- wp:column --> <div class="wp-block-column"><!-- wp:paragraph --> <p>As Robert May summarised in a paper published in <em>Science</em>{ref}May, R. M. (2010). <a href="https://science.sciencemag.org/content/329/5987/41.summary">Tropical arthropod species, more or less?</a>. <em>Science</em>, <em>329</em>(5987), 41-42.{/ref}:</p> <!-- /wp:paragraph --> <!-- wp:quote --> <blockquote class="wp-block-quote"><p>If some alien version of the Starship Enterprise visited Earth, what might be the visitors' first question? I think it would be: “How many distinct life forms—species—does your planet have?” Embarrassingly, our best-guess answer would be in the range of 5 to 10 million eukaryotes (never mind the viruses and bacteria), but we could defend numbers exceeding 100 million, or as low as 3 million.</p></blockquote> <!-- /wp:quote --> <!-- wp:paragraph --> <p>Researchers have come up with wide-ranging estimates for how many species there are. As May points out, this ranges anywhere from 3 to well over 100 million – many orders of magnitude of difference. Some more recent studies estimate that this figure is as much as one trillion.</p> <!-- /wp:paragraph --> <!-- wp:paragraph --> <p>One of the most widely cited figures comes from Camilo Mora and colleagues; they estimated that there are around 8.7 million species on Earth today.{ref}Mora, C., Tittensor, D. P., Adl, S., Simpson, A. G., & Worm, B. (2011). How many species are there on Earth and in the ocean?. PLoS Biol, 9(8), e1001127.{/ref} Costello et al. (2013) estimate 5 ± 3 million species; Chapman (2009) estimate 11 million; and after reviewing the range in the literature, Scheffers et al. (2012) choose not to give a concrete figure at all.{ref}</p> <!-- /wp:paragraph --> <!-- wp:paragraph --> <p>Costello, M. J., May, R. M., & Stork, N. E. (2013). Can we name Earth’s species before they go extinct?. Science, 339(6118), 413-416.</p> <!-- /wp:paragraph --> <!-- wp:paragraph --> <p>A. D. Chapman, Numbers of Living Species in Australia and the World (Biodiversity Information Services, Toowoomba, Australia, 2009).</p> <!-- /wp:paragraph --> <!-- wp:paragraph --> <p>Scheffers, B. R., Joppa, L. N., Pimm, S. L., & Laurance, W. F. (2012). What we know and don’t know about Earth’s missing biodiversity. Trends in ecology & evolution, 27(9), 501-510.{/ref} More recent studies suggest that the true number is in the billions.</p> <!-- /wp:paragraph --> <!-- wp:paragraph --> <p>Why is there such large disagreement on the number of species?</p> <!-- /wp:paragraph --> <!-- wp:paragraph --> <p>The first challenge is even defining what a ‘species’ is. Even in well-known taxonomic groups – such as birds or reptiles – the delineation of species can change over time.{ref}Tobias, J. A., Seddon, N., Spottiswoode, C. N., Pilgrim, J. D., Fishpool, L. D., & Collar, N. J. (2010). Quantitative criteria for species delimitation. Ibis, 152(4), 724-746.{/ref} Our scientific understanding of organisms, and their relationship to others is still improving. That can mean ‘splitting’ a species into multiple, or combining ‘separate species’ into a single one. A <a href="https://britishbirds.co.uk/content/bb%C2%A0eye%C2%A0do-taxonomic-changes-affect-conservation">clear example</a> of this was when a BirdLife International Review split the Red-bellied Pitta – which was formerly a single bird species – into twelve separate species.</p> <!-- /wp:paragraph --> <!-- wp:paragraph --> <p>The second challenge is coming up with estimates for groups that are less well-studied than mammals, birds, and reptiles. Most of the disagreement lies is in insects, fungi, and other smaller microbial species. Reaching a consensus on such small and inaccessible lifeforms is undoubtedly hard. There are between 6000 to 7000 known mammal species, but 350,000 - 400,000 of described species of beetles.{ref}Stork, N. E., McBroom, J., Gely, C., & Hamilton, A. J. (2015). New approaches narrow global species estimates for beetles, insects, and terrestrial arthropods. Proceedings of the National Academy of Sciences, 112(24), 7519-7523.{/ref}</p> <!-- /wp:paragraph --> <!-- wp:paragraph --> <p>The biggest area of uncertainty in species estimates is for bacteria and archaea. This can range from mere thousands to billions.{ref}Dykhuizen, D. (2005). Species numbers in bacteria. Proceedings. California Academy of Sciences, 56(6 Suppl 1), 62.{/ref} A 2017 paper by Larsen et al. estimates that there are 1 to 6 billion species on Earth, and bacteria make up 70% to 90% of them.{ref}Larsen, B. B., Miller, E. C., Rhodes, M. K., & Wiens, J. J. (2017). Inordinate fondness multiplied and redistributed: the number of species on earth and the new pie of life. The Quarterly Review of Biology, 92(3), 229-265.{/ref} </p> <!-- /wp:paragraph --> <!-- wp:paragraph --> <p>The honest answer to the question, “How many species are there?” is that we don’t really know. Estimates span several orders of magnitude, from a few million to billions. Most recent estimates lean towards the higher range. The biggest uncertainty is in the small lifeforms – bacteria and archaea – where we’ve only described a small percentage of the total.</p> <!-- /wp:paragraph --></div> <!-- /wp:column --> <!-- wp:column --> <div class="wp-block-column"></div> <!-- /wp:column --></div> <!-- /wp:columns --> <!-- wp:separator --> <hr class="wp-block-separator"/> <!-- /wp:separator --> <!-- wp:paragraph --> <p><strong><em>Update: This article was updated in February 2024 with more discussion on the uncertainty of estimates on the number of species globally.</em></strong></p> <!-- /wp:paragraph --> | {
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2022-11-30 11:42:49 | 2024-03-09 18:11:26 | 1iHlA_srDqieTz8-l5HHfHdLMRju6BlWQ5FAnXBw5ak8 | [
"Hannah Ritchie"
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How many species do we share our planet with? How many of these species have we found and identified? | 2022-11-30 11:42:49 | 2024-02-05 17:42:57 | https://ourworldindata.org/wp-content/uploads/2022/11/Number-of-species-thumbnail.png | {} |
How many species do we share our planet with? It's such a basic and fundamental question to understanding the world around us. It's almost unthinkable that we would not know this number or at least have a good estimate. But the truth is that it's a question that continues to escape the world's taxonomists. An important distinction is **how many species we have identified and described** and how many species there actually are. We've only identified a small fraction of the world's species, so these numbers are very different. ## How many species have we _described_? Before we look at estimates of how many species there are in total, we should first ask the question of how many species we _know that we know. _Species that we have identified and named. The [IUCN Red List](https://www.iucnredlist.org/resources/summary-statistics) tracks the number of described species and updates this figure annually based on the latest work of taxonomists. In 2021, it listed 2.13 million species on the planet. In the chart, we see the breakdown across a range of taxonomic groups – 1.05 million insects, over 11,000 birds, over 11,000 reptiles, and over 6,000 mammals. These figures – particularly for lesser-known groups such as plants or fungi – might be a bit too high. This is because some described species are synonyms – the description of already-known species, simply given a separate name.{ref}Costello, M. J., May, R. M., & Stork, N. E. (2013). Can we name Earth's species before they go extinct?. Science, 339(6118), 413-416.{/ref} There is a continual evaluation process to remove synonyms (and most are removed eventually), but often species are added at a faster rate than synonyms can be found and removed.{ref}Solow, A. R., Mound, L. A., & Gaston, K. J. (1995). Estimating the rate of synonymy. Systematic Biology, 44(1), 93-96.{/ref} To give a sense of how large this effect might be, in a study published in Science, Costello et al. (2013) estimated that around 20% of the described species were undiscovered synonyms (in other words, duplicates).{ref}Costello, M. J., May, R. M., & Stork, N. E. (2013). Can we name Earth's species before they go extinct?. Science, 339(6118), 413-416.{/ref} They estimated that the 1.9 million described species at the time were actually closer to 1.5 million unique species. If we were to assume this "20% synonym" figure held true, our 2.12 million described species might actually be closer to 1.7 million. Regardless, we know that all these figures underestimate the actual number of species. The fact that there are so many species that we've yet to discover has real consequences for our ability to understand changes in global biodiversity and the rate of species extinctions. If we don't know that certain species exist, we also don't know that they might have, or will soon, go extinct. Some species will inevitably go extinct before we realize that they used to exist. <Chart url="https://ourworldindata.org/grapher/number-of-described-species?country=Fishes~Insects~Reptiles~Mammals~Birds~Amphibians~Corals~Molluscs~Crustaceans~Arachnids~All+groups~Fungi+and+Protists"/> ## How many species are there really? As Robert May summarised in a paper published in _Science_{ref}May, R. M. (2010). [Tropical arthropod species, more or less?](https://science.sciencemag.org/content/329/5987/41.summary). _Science_, _329_(5987), 41-42.{/ref}: -- undefined Researchers have come up with wide-ranging estimates for how many species there are. As May points out, this ranges anywhere from 3 to well over 100 million – many orders of magnitude of difference. Some more recent studies estimate that this figure is as much as one trillion. One of the most widely cited figures comes from Camilo Mora and colleagues; they estimated that there are around 8.7 million species on Earth today.{ref}Mora, C., Tittensor, D. P., Adl, S., Simpson, A. G., & Worm, B. (2011). How many species are there on Earth and in the ocean?. PLoS Biol, 9(8), e1001127.{/ref} Costello et al. (2013) estimate 5 ± 3 million species; Chapman (2009) estimate 11 million; and after reviewing the range in the literature, Scheffers et al. (2012) choose not to give a concrete figure at all.{ref} Costello, M. J., May, R. M., & Stork, N. E. (2013). Can we name Earth’s species before they go extinct?. Science, 339(6118), 413-416. A. D. Chapman, Numbers of Living Species in Australia and the World (Biodiversity Information Services, Toowoomba, Australia, 2009). Scheffers, B. R., Joppa, L. N., Pimm, S. L., & Laurance, W. F. (2012). What we know and don’t know about Earth’s missing biodiversity. Trends in ecology & evolution, 27(9), 501-510.{/ref} More recent studies suggest that the true number is in the billions. Why is there such large disagreement on the number of species? The first challenge is even defining what a ‘species’ is. Even in well-known taxonomic groups – such as birds or reptiles – the delineation of species can change over time.{ref}Tobias, J. A., Seddon, N., Spottiswoode, C. N., Pilgrim, J. D., Fishpool, L. D., & Collar, N. J. (2010). Quantitative criteria for species delimitation. Ibis, 152(4), 724-746.{/ref} Our scientific understanding of organisms, and their relationship to others is still improving. That can mean ‘splitting’ a species into multiple, or combining ‘separate species’ into a single one. A [clear example](https://britishbirds.co.uk/content/bb%C2%A0eye%C2%A0do-taxonomic-changes-affect-conservation) of this was when a BirdLife International Review split the Red-bellied Pitta – which was formerly a single bird species – into twelve separate species. The second challenge is coming up with estimates for groups that are less well-studied than mammals, birds, and reptiles. Most of the disagreement lies is in insects, fungi, and other smaller microbial species. Reaching a consensus on such small and inaccessible lifeforms is undoubtedly hard. There are between 6000 to 7000 known mammal species, but 350,000 - 400,000 of described species of beetles.{ref}Stork, N. E., McBroom, J., Gely, C., & Hamilton, A. J. (2015). New approaches narrow global species estimates for beetles, insects, and terrestrial arthropods. Proceedings of the National Academy of Sciences, 112(24), 7519-7523.{/ref} The biggest area of uncertainty in species estimates is for bacteria and archaea. This can range from mere thousands to billions.{ref}Dykhuizen, D. (2005). Species numbers in bacteria. Proceedings. California Academy of Sciences, 56(6 Suppl 1), 62.{/ref} A 2017 paper by Larsen et al. estimates that there are 1 to 6 billion species on Earth, and bacteria make up 70% to 90% of them.{ref}Larsen, B. B., Miller, E. C., Rhodes, M. K., & Wiens, J. J. (2017). Inordinate fondness multiplied and redistributed: the number of species on earth and the new pie of life. The Quarterly Review of Biology, 92(3), 229-265.{/ref} The honest answer to the question, “How many species are there?” is that we don’t really know. Estimates span several orders of magnitude, from a few million to billions. Most recent estimates lean towards the higher range. The biggest uncertainty is in the small lifeforms – bacteria and archaea – where we’ve only described a small percentage of the total. **_Update: This article was updated in February 2024 with more discussion on the uncertainty of estimates on the number of species globally._** | {
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"rendered": "\n<p>How many species do we share our planet with? It’s such a basic and fundamental question to understanding the world around us. </p>\n\n\n\n<p>It’s almost unthinkable that we would not know this number or at least have a good estimate. But the truth is that it’s a question that continues to escape the world’s taxonomists.</p>\n\n\n\n<p>An important distinction is <strong>how many species we have identified and described</strong> and how many species there actually are. We’ve only identified a small fraction of the world’s species, so these numbers are very different.</p>\n\n\n\n<h3>How many species have we <em>described</em>?</h3>\n\n\n\n<div class=\"wp-block-columns\">\n<div class=\"wp-block-column\">\n<p>Before we look at estimates of how many species there are in total, we should first ask the question of how many species we <em>know that we know. </em>Species that we have identified and named.</p>\n\n\n\n<p>The <a href=\"https://www.iucnredlist.org/resources/summary-statistics\">IUCN Red List</a> tracks the number of described species and updates this figure annually based on the latest work of taxonomists. In 2021, it listed 2.13 million species on the planet. In the chart, we see the breakdown across a range of taxonomic groups \u2013 1.05 million insects, over 11,000 birds, over 11,000 reptiles, and over 6,000 mammals.</p>\n\n\n\n<p>These figures \u2013 particularly for lesser-known groups such as plants or fungi \u2013 might be a bit too high. This is because some described species are synonyms \u2013 the description of already-known species, simply given a separate name.{ref}Costello, M. J., May, R. M., & Stork, N. E. (2013). Can we name Earth’s species before they go extinct?. Science, 339(6118), 413-416.{/ref} There is a continual evaluation process to remove synonyms (and most are removed eventually), but often species are added at a faster rate than synonyms can be found and removed.{ref}Solow, A. R., Mound, L. A., & Gaston, K. J. (1995). Estimating the rate of synonymy. Systematic Biology, 44(1), 93-96.{/ref} To give a sense of how large this effect might be, in a study published in Science, Costello et al. (2013) estimated that around 20% of the described species were undiscovered synonyms (in other words, duplicates).{ref}Costello, M. J., May, R. M., & Stork, N. E. (2013). Can we name Earth’s species before they go extinct?. Science, 339(6118), 413-416.{/ref} They estimated that the 1.9 million described species at the time were actually closer to 1.5 million unique species.</p>\n\n\n\n<p>If we were to assume this “20% synonym” figure held true, our 2.12 million described species might actually be closer to 1.7 million.</p>\n\n\n\n<p>Regardless, we know that all these figures underestimate the actual number of species. The fact that there are so many species that we’ve yet to discover has real consequences for our ability to understand changes in global biodiversity and the rate of species extinctions. </p>\n\n\n\n<p>If we don’t know that certain species exist, we also don’t know that they might have, or will soon, go extinct. Some species will inevitably go extinct before we realize that they used to exist.</p>\n</div>\n\n\n\n<div class=\"wp-block-column\">\n<iframe src=\"https://ourworldindata.org/grapher/number-of-described-species?country=Fishes~Insects~Reptiles~Mammals~Birds~Amphibians~Corals~Molluscs~Crustaceans~Arachnids~All+groups~Fungi+and+Protists\" loading=\"lazy\" style=\"width: 100%; height: 600px; border: 0px none;\"></iframe>\n</div>\n</div>\n\n\n\n<h3>How many species are there really?</h3>\n\n\n\n<div class=\"wp-block-columns\">\n<div class=\"wp-block-column\">\n<p>As Robert May summarised in a paper published in <em>Science</em>{ref}May, R. M. (2010). <a href=\"https://science.sciencemag.org/content/329/5987/41.summary\">Tropical arthropod species, more or less?</a>. <em>Science</em>, <em>329</em>(5987), 41-42.{/ref}:</p>\n\n\n\n<blockquote class=\"wp-block-quote\"><p>If some alien version of the Starship Enterprise visited Earth, what might be the visitors’ first question? I think it would be: \u201cHow many distinct life forms\u2014species\u2014does your planet have?\u201d Embarrassingly, our best-guess answer would be in the range of 5 to 10 million eukaryotes (never mind the viruses and bacteria), but we could defend numbers exceeding 100 million, or as low as 3 million.</p></blockquote>\n\n\n\n<p>Researchers have come up with wide-ranging estimates for how many species there are. As May points out, this ranges anywhere from 3 to well over 100 million \u2013 many orders of magnitude of difference. Some more recent studies estimate that this figure is as much as one trillion.</p>\n\n\n\n<p>One of the most widely cited figures comes from Camilo Mora and colleagues; they estimated that there are around 8.7 million species on Earth today.{ref}Mora, C., Tittensor, D. P., Adl, S., Simpson, A. G., & Worm, B. (2011). How many species are there on Earth and in the ocean?. PLoS Biol, 9(8), e1001127.{/ref} Costello et al. (2013) estimate 5 \u00b1 3 million species; Chapman (2009) estimate 11 million; and after reviewing the range in the literature, Scheffers et al. (2012) choose not to give a concrete figure at all.{ref}</p>\n\n\n\n<p>Costello, M. J., May, R. M., & Stork, N. E. (2013). Can we name Earth\u2019s species before they go extinct?. Science, 339(6118), 413-416.</p>\n\n\n\n<p>A. D. Chapman, Numbers of Living Species in Australia and the World (Biodiversity Information Services, Toowoomba, Australia, 2009).</p>\n\n\n\n<p>Scheffers, B. R., Joppa, L. N., Pimm, S. L., & Laurance, W. F. (2012). What we know and don\u2019t know about Earth\u2019s missing biodiversity. Trends in ecology & evolution, 27(9), 501-510.{/ref} More recent studies suggest that the true number is in the billions.</p>\n\n\n\n<p>Why is there such large disagreement on the number of species?</p>\n\n\n\n<p>The first challenge is even defining what a \u2018species\u2019 is. Even in well-known taxonomic groups \u2013 such as birds or reptiles \u2013 the delineation of species can change over time.{ref}Tobias, J. A., Seddon, N., Spottiswoode, C. N., Pilgrim, J. D., Fishpool, L. D., & Collar, N. J. (2010). Quantitative criteria for species delimitation. Ibis, 152(4), 724-746.{/ref} Our scientific understanding of organisms, and their relationship to others is still improving. That can mean \u2018splitting\u2019 a species into multiple, or combining \u2018separate species\u2019 into a single one. A <a href=\"https://britishbirds.co.uk/content/bb%C2%A0eye%C2%A0do-taxonomic-changes-affect-conservation\">clear example</a> of this was when a BirdLife International Review split the Red-bellied Pitta \u2013 which was formerly a single bird species \u2013 into twelve separate species.</p>\n\n\n\n<p>The second challenge is coming up with estimates for groups that are less well-studied than mammals, birds, and reptiles. Most of the disagreement lies is in insects, fungi, and other smaller microbial species. Reaching a consensus on such small and inaccessible lifeforms is undoubtedly hard. There are between 6000 to 7000 known mammal species, but 350,000 – 400,000 of described species of beetles.{ref}Stork, N. E., McBroom, J., Gely, C., & Hamilton, A. J. (2015). New approaches narrow global species estimates for beetles, insects, and terrestrial arthropods. Proceedings of the National Academy of Sciences, 112(24), 7519-7523.{/ref}</p>\n\n\n\n<p>The biggest area of uncertainty in species estimates is for bacteria and archaea. This can range from mere thousands to billions.{ref}Dykhuizen, D. (2005). Species numbers in bacteria. Proceedings. California Academy of Sciences, 56(6 Suppl 1), 62.{/ref} A 2017 paper by Larsen et al. estimates that there are 1 to 6 billion species on Earth, and bacteria make up 70% to 90% of them.{ref}Larsen, B. B., Miller, E. C., Rhodes, M. K., & Wiens, J. J. (2017). Inordinate fondness multiplied and redistributed: the number of species on earth and the new pie of life. The Quarterly Review of Biology, 92(3), 229-265.{/ref}\u00a0</p>\n\n\n\n<p>The honest answer to the question, \u201cHow many species are there?\u201d is that we don\u2019t really know. Estimates span several orders of magnitude, from a few million to billions. Most recent estimates lean towards the higher range. The biggest uncertainty is in the small lifeforms \u2013 bacteria and archaea \u2013 where we\u2019ve only described a small percentage of the total.</p>\n</div>\n\n\n\n<div class=\"wp-block-column\"></div>\n</div>\n\n\n\n<hr class=\"wp-block-separator\"/>\n\n\n\n<p><strong><em>Update: This article was updated in February 2024 with more discussion on the uncertainty of estimates on the number of species globally.</em></strong></p>\n",
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