Global biodiversity explained

Global biodiversity is the measure of biodiversity on planet Earth and is defined as the total variability of life forms. More than 99 percent of all species[1] that ever lived on Earth are estimated to be extinct.[2] [3] Estimates on the number of Earth's current species range from 2 million to 1 trillion, but most estimates are around 11 million species or fewer. About 1.74 million species were databased as of 2018,[4] and over 80 percent have not yet been described.[5] The total amount of DNA base pairs on Earth, as a possible approximation of global biodiversity, is estimated at 5.0 x 1037, and weighs 50 billion tonnes.[6] In comparison, the total mass of the biosphere has been estimated to be as much as 4 TtC (trillion tons of carbon).[7]

In other related studies, around 1.9 million extant species are believed to have been described currently,[8] but some scientists believe 20% are synonyms, reducing the total valid described species to 1.5 million. In 2013, a study published in Science estimated there to be 5 ± 3 million extant species on Earth although that is disputed.[9] Another study, published in 2011 by PLoS Biology, estimated there to be 8.7 million ± 1.3 million eukaryotic species on Earth.[10] Some 250,000 valid fossil species have been described, but this is believed to be a small proportion of all species that have ever lived.

Global biodiversity is affected by extinction and speciation. The background extinction rate varies among taxa but it is estimated that there is approximately one extinction per million species years. Mammal species, for example, typically persist for 1 million years. Biodiversity has grown and shrunk in earth's past due to (presumably) abiotic factors such as extinction events caused by geologically rapid changes in climate. Climate change 299 million years ago was one such event. A cooling and drying resulted in catastrophic rainforest collapse and subsequently a great loss of diversity, especially of amphibians.[11]

Known species

Chapman, 2005 and 2009 has attempted to compile perhaps the most comprehensive recent statistics on numbers of extant species, drawing on a range of published and unpublished sources, and has come up with a figure of approximately 1.9 million estimated described taxa, as against possibly a total of between 11 and 12 million anticipated species overall (described plus undescribed), though other reported values for the latter vary widely. In many cases, the values given for "Described" species are an estimate only (sometimes a mean of reported figures in the literature) since for many of the larger groups in particular, comprehensive lists of valid species names do not currently exist. For fossil species, exact or even approximate numbers are harder to find; Raup, 1986[12] includes data based on a compilation of 250,000 fossil species so the true number is undoubtedly somewhat higher than this. The number of described species is increasing by around 18,000–19,000 extant, and approaching 2,000 fossil species each year, as of 2012.[13] [14] [15] The number of published species names is higher than the number of described species, sometimes considerably so, on account of the publication, through time, of multiple names (synonyms) for the same accepted taxon in many cases.

Based on Chapman's (2009) report, the estimated numbers of described extant species as of 2009 can be broken down as follows:
Major/Component group Described Global estimate (described + undescribed)
64,788 ~80,500
5,487 ~5,500
9,990 >10,000
8,734 ~10,000
6,515 ~15,000
31,153 ~40,000
116 unknown
33 unknown
2,760 unknown
~1,359,365 ~6,755,830
108 ~110
7,003 ~14,000
~1,000,000 (965,431–1,015,897) ~5,000,000
470
3,684–4,000
360,000–~400,000 1,100,000
1,816
152,956 240,000
200–300 2,000
2,500–<3,000
80,000–88,000
115,000 >~1,000,000[16]
2,600–2,800 4,000
174,250 300,000–500,000
2,200
481
250–300
~5,000
55
6,500
24,380
Phasmatodea (Phasmida) 2,500–3,300
>3,000–~3,200
2,274
3,200–~3,500
2,525
596
~6,000
12,627
28
Zygentoma (Thysanura) 370
102,248 ~600,000
1,340 unknown
16,072 ~90,000
47,000 150,000
165 ~220
9,048 52,000
~85,000 ~200,000
16,763 ~30,000
<25,000 ~500,000
1,150 ~1,500
20,000 ~80,000
9,795 unknown
~6,000 ~18,000
Other Invertebrates 12,673 ~20,000
1 -
1 -
Mesozoa (Rhombozoa, Orthonectida) 106 -
166 200
Nemertea (Nemertina) 1,200 5,000–10,000
2,180 -
400 -
130 -
331 ~2,000
Entoprocta (Kamptozoa) 170 170
97 -
16 -
28 >100
1 -
144 -
176 -
1,045 -
10 -
Ectoprocta (Bryozoa) 5,700 ~5,000
550 -
100 -
121 -
Plants sens. lat. ~310,129 ~390,800
16,236 ~22,750
~5,000 ~7,500
236 ~250
~11,000 ~15,000
Algae (Plant) 12,272 unknown
2,125 -
4,045 -
5 -
6,097 -
281,621 ~368,050
~12,000 ~15,000
~1,021 ~1,050
~268,600 ~352,000
98,998 (incl. Lichens 17,000) 1,500,000 (incl. Lichens ~25,000)
Others ~66,307 ~2,600,500
Chromista [incl. [[brown algae]], diatoms and other groups] 25,044 ~200,500
Protoctista [i.e. residual protist groups] ~28,871 >1,000,000
Prokaryota [[[Bacteria]] and Archaea, excl. Cyanophyta] 7,643 ~1,000,000
2,664 unknown
2,085 400,000
Total (2009 data) 1,899,587 ~11,327,630

Estimates of total number of species

However the total number of species for some taxa may be much higher.

In 1982, Terry Erwin published an estimate of global species richness of 30 million, by extrapolating from the numbers of beetles found in a species of tropical tree. In one species of tree, Erwin identified 1200 beetle species, of which he estimated 163 were found only in that type of tree.[23] Given the 50,000 described tropical tree species, Erwin suggested that there are almost 10 million beetle species in the tropics.[24] In 2011 a study published in PLoS Biology estimated there to be 8.7 million ± 1.3 million eukaryotic species on Earth.[10]

By 2017, most estimates projected there to be around 11 million species or fewer on Earth. A 2017 study estimated there are around at least 1 to 6 billion species, 70-90% of which are bacteria.[25] A May 2016 study based on scaling laws estimated that 1 trillion species (overwhelmingly microbes) are on Earth currently with only one-thousandth of one percent described,[26] [27] though this has been controversial and a 2019 study of varied environmental samples of 16S ribosomal RNA estimated that there exist 0.8-1.6 million species of prokaryotes.[28]

Indices to describe trends

After the Convention on Biological Diversity was signed in 1992, biological conservation became a priority for the international community. There are several indicators used that describe trends in global biodiversity. However, there is no single indicator for all extant species as not all have been described and measured over time. There are different ways to measure changes in biodiversity. The Living Planet Index (LPI) is a population-based indicator that combines data from individual populations of many vertebrate species to create a single index.[29] The Global LPI for 2012 decreased by 28%. There are also indices that separate temperate and tropical species for marine and terrestrial species.

The Red List Index is based on the IUCN Red List of Threatened Species and measures changes in conservation status over time and currently includes taxa that have been completely categorized: mammals, birds, amphibians and corals.[30] The Global Wild Bird Index is another indicator that shows trends in population of wild bird groups on a regional scale from data collected in formal surveys.[31] Challenges to these indices due to data availability are taxonomic gaps and the length of time of each index.

The Biodiversity Indicators Partnership was established in 2006 to assist biodiversity indicator development, advancement and to increase the availability of indicators.

See also

External links

Notes and References

  1. Book: McKinney . Michael L. . How do rare species avoid extinction? A paleontological view . Kunin . W. E. . Gaston . K. J. . The Biology of Rarity: Causes and consequences of rare—common differences . 6 December 2012 . Springer Science & Business Media . 978-94-011-5874-9 . https://books.google.com/books?id=4LHnCAAAQBAJ&pg=PA110 . en . 110.
  2. Book: Stearns . Beverly Peterson . Stearns . Stephen C. . Watching, from the Edge of Extinction . 1999 . Yale University Press . 978-0-300-08469-6 . en . x.
  3. News: Novacek . Michael J. . 8 November 2014 . Prehistory's Brilliant Future . The New York Times . New York . 0362-4331 . 2014-12-25.
  4. Web site: Catalogue of Life: 2018 Annual Checklist . 2018 . 2018-08-20.
  5. Mora . Camilo . Tittensor . Derek P. . Adl . Sina . Simpson . Alastair G. B. . Worm . Boris . Boris Worm . 3 . 23 August 2011 . How Many Species Are There on Earth and in the Ocean? . . San Francisco, CA . . 9 . 8 . e1001127 . 10.1371/journal.pbio.1001127 . 1545-7885 . 3160336 . 21886479 . free .
  6. News: Nuwer . Rachel . Rachel Nuwer . 18 July 2015 . Counting All the DNA on Earth . The New York Times . New York . 0362-4331 . 2015-07-18.
  7. Web site: The Biosphere: Diversity of Life . . Aspen Global Change Institute . Basalt, CO . 2015-07-19 . 2021-05-04 . https://web.archive.org/web/20210504055705/https://www.agci.org/earth-systems/biosphere . dead .
  8. Book: Numbers of Living Species in Australia and the World . Chapman, A. D. . 2009 . Australian Biological Resources Study . Canberra . 2nd . 1–80 . PDF . 978-0-642-56861-8.
  9. Costello. Mark. Robert May . Nigel Stork . 20757947. Can we name Earth's species before they go extinct?. Science. 25 January 2013. 339. 10.1126/science.1230318. 23349283. 6118. 413–416. 2013Sci...339..413C.
  10. Sweetlove. Lee. Number of species on Earth tagged at 8.7 million. Nature. 2011 . Macmillan Publishers Limited. 10.1038/news.2011.498 . 18 July 2014.
  11. Sahney, S. . Benton, M.J. . Falcon-Lang, H.J. . 2010 . Rainforest collapse triggered Pennsylvanian tetrapod diversification in Euramerica . Geology . 38 . 1079–1082 . 10.1130/G31182.1 . 12. 2010Geo....38.1079S .
  12. Raup. D.M. . 23012011 . 1986 . Biological extinction in earth history . Science . 231 . 1528–1533 . 10.1126/science.11542058 . 4745 . 11542058. 1986Sci...231.1528R .
  13. Book: SOS 2009: State of Observed Species . IISE . 2010 . International Institute for Species Exploration . Arizona State University . 1–8 . PDF . 2013-09-16 . 2013-09-22 . https://web.archive.org/web/20130922091928/http://species.asu.edu/SOS_2009 . dead .
  14. Book: SOS 2010: State of Observed Species . IISE . 2011 . International Institute for Species Exploration . Arizona State University . 1–10 . PDF . 2013-09-16 . 2013-09-22 . https://web.archive.org/web/20130922093805/http://species.asu.edu/SOS_2010 . dead .
  15. Book: SOS 2011: State of Observed Species . IISE . 2012 . International Institute for Species Exploration . Arizona State University . 1–14 . PDF .
  16. Forbes et al. . Quantifying the unquantifiable: why Hymenoptera, not Coleoptera, is the most speciose animal order . BMC Ecology . 2018 . 18 . 1 . 21 . 10.1186/s12898-018-0176-x . free . 30001194 . 6042248 .
  17. Web site: Numbers of Insects (Species and Individuals) . Smithsonian Institution. 1996.
  18. Proceedings of the National Academy of Sciences, Census of Marine Life (CoML) BBC News
  19. David L. Hawksworth, "The magnitude of fungal diversity: the 1•5 million species estimate revisited" Mycological Research (2001), 105: 1422-1432 Cambridge University Press Abstract
  20. Web site: Acari at University of Michigan Museum of Zoology Web Page. insects.ummz.lsa.umich.edu.
  21. Pawlowski, J. et al. (2012). CBOL Protist Working Group: Barcoding Eukaryotic Richness beyond the Animal, Plant, and Fungal Kingdoms. PLoS Biol 10(11): e1001419. doi:10.1371/journal.pbio.1001419, https://hal.archives-ouvertes.fr/hal-01258240/document.
  22. Adl, S. M. et al. (2007). Diversity, nomenclature, and taxonomy of protists. Systematic Biology 56(4), 684-689, https://www.researchgate.net/profile/Sina_Adl/publication/6178284_Diversity_nomenclature_and_taxonomy_of_protists/links/0fcfd50a6b61dcb2b8000000.pdf.
  23. Terry L.. Erwin. Terry Erwin. Tropical Forests: Their Richness in Coleoptera and Other Arthropod Species. The Coleopterists Bulletin. The Coleopterists Society. 36. 1. March 1982. 74–75. 0010-065X. 4007977.
  24. Book: Pullin, Andrew. 2002. Conservation Biology. Cambridge. Cambridge University Press. 9780521644822 . December 24, 2013.
  25. Larsen . Brendan B. . Miller . Elizabeth C. . Rhodes . Matthew K. . Wiens . John J. . Inordinate Fondness Multiplied and Redistributed: the Number of Species on Earth and the New Pie of Life . The Quarterly Review of Biology . September 2017 . 92 . 3 . 229–265 . 10.1086/693564 . 6 August 2023 . en . 0033-5770.
  26. Web site: Researchers find that Earth may be home to 1 trillion species . NSF . 2 May 2016. 6 May 2016.
  27. Locey, Lennon . Scaling laws predict global microbial diversity . Proceedings of the National Academy of Sciences of the United States of America . 2016 . 113 . 21 . 5970–5975 . 10.1073/pnas.1521291113 . 27140646 . 4889364 . 2016PNAS..113.5970L . free .
  28. Louca . Stilianos . Mazel . Florent . Doebeli . Michael . Parfrey . Laura Wegener . A census-based estimate of Earth's bacterial and archaeal diversity . PLOS Biology . 4 February 2019 . 17 . 2 . e3000106 . 10.1371/journal.pbio.3000106 . 30716065 . en . 1545-7885. 6361415 . free .
  29. Web site: Indicators and Assessments Unit . Zoological Society of London.
  30. Web site: Trends in the status of biodiversity . 25 November 2013 . IUCN.
  31. Web site: Global Wild Bird Index . dead . https://web.archive.org/web/20131202225749/http://www.bipindicators.net/wbi . 2013-12-02 . 2013-11-25 . Biodiversity Indicators Partnership.