Global biodiversity
{{short description|Total variability of Earth's life forms}}
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{{cite book |last1=McKinney |first1=Michael L. |chapter=How do rare species avoid extinction? A paleontological view |editor-last1=Kunin |editor-first1=W. E. |editor-last2=Gaston |editor-first2=K. J. |title=The Biology of Rarity: Causes and consequences of rare—common differences |date=6 December 2012 |publisher=Springer Science & Business Media |isbn=978-94-011-5874-9 |chapter-url=https://books.google.com/books?id=4LHnCAAAQBAJ&pg=PA110 |language=en |page=110}} that ever lived on Earth are estimated to be extinct.{{cite book |last1=Stearns |first1=Beverly Peterson |last2=Stearns |first2=Stephen C. |title=Watching, from the Edge of Extinction |date=1999 |publisher=Yale University Press |isbn=978-0-300-08469-6 |url=https://books.google.com/books?id=0BHeC-tXIB4C&pg=PA1921 |language=en |page=x}}{{cite news |last=Novacek |first=Michael J. |date=8 November 2014 |title=Prehistory's Brilliant Future |url=https://www.nytimes.com/2014/11/09/opinion/sunday/prehistorys-brilliant-future.html |newspaper=The New York Times |location=New York |issn=0362-4331 |accessdate=2014-12-25}} 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,{{cite web |url=http://www.catalogueoflife.org/annual-checklist/2018/info/ac |title=Catalogue of Life: 2018 Annual Checklist |year=2018 |accessdate=2018-08-20}} and over 80 percent have not yet been described.{{cite journal |last1=Mora |first1=Camilo |last2=Tittensor |first2=Derek P. |last3=Adl |first3=Sina |last4=Simpson |first4=Alastair G. B. |last5=Worm |first5=Boris |authorlink5=Boris Worm |display-authors=3 |date=23 August 2011 |title=How Many Species Are There on Earth and in the Ocean? |journal=PLOS Biology |location=San Francisco, CA |publisher=PLOS |volume=9 |issue=8 |page=e1001127 |doi=10.1371/journal.pbio.1001127 |issn=1545-7885 |pmc=3160336 |pmid=21886479 |doi-access=free }} 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.{{cite news |last=Nuwer |first=Rachel |author-link=Rachel Nuwer |date=18 July 2015 |title=Counting All the DNA on Earth |url=https://www.nytimes.com/2015/07/21/science/counting-all-the-dna-on-earth.html |work=The New York Times |location=New York |issn=0362-4331 |accessdate=2015-07-18}} In comparison, the total mass of the biosphere has been estimated to be as much as 4 TtC (trillion tons of carbon).{{cite web |url=http://www.agci.org/classroom/biosphere/index.php |title=The Biosphere: Diversity of Life |author= |work=Aspen Global Change Institute |location=Basalt, CO |accessdate=2015-07-19 |archive-date=2021-05-04 |archive-url=https://web.archive.org/web/20210504055705/https://www.agci.org/earth-systems/biosphere |url-status=dead }}
In other related studies, around 1.9 million extant species are believed to have been described currently,{{ cite book | url=http://www.environment.gov.au/biodiversity/abrs/publications/other/species-numbers/2009/index.html | author= Chapman, A. D. | year=2009 | title=Numbers of Living Species in Australia and the World | publisher=Australian Biological Resources Study | location=Canberra | edition=2nd | pages=1–80 | format=PDF | isbn=978-0-642-56861-8}} 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.{{cite journal|last=Costello|first=Mark|author2=Robert May |author3=Nigel Stork |s2cid=20757947|title=Can we name Earth's species before they go extinct?|journal=Science|date=25 January 2013|volume=339|doi=10.1126/science.1230318|pmid=23349283|issue=6118|pages=413–416|bibcode=2013Sci...339..413C}} Another study, published in 2011 by PLoS Biology, estimated there to be 8.7 million ± 1.3 million eukaryotic species on Earth.{{cite journal|last1=Sweetlove|first1=Lee|title=Number of species on Earth tagged at 8.7 million|url=http://www.nature.com/news/2011/110823/full/news.2011.498.html|journal=Nature|year=2011 |publisher=Macmillan Publishers Limited|doi=10.1038/news.2011.498 |accessdate=18 July 2014}} 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.{{Citation | title=Bringing Fossils to Life: An Introduction to Paleobiology | edition=3rd | author=Donald R. Prothero | date=2013 | pages=21 | publisher=Columbia University Press }}
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.{{ cite journal |author1=Sahney, S. |author2=Benton, M.J. |author3=Falcon-Lang, H.J. | year=2010 | title= Rainforest collapse triggered Pennsylvanian tetrapod diversification in Euramerica | journal=Geology | volume = 38 | pages = 1079–1082 | doi=10.1130/G31182.1 | issue=12| bibcode=2010Geo....38.1079S }}
Known species
Image:Hoverflies mating midair.jpg
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{{ cite journal | author=Raup. D.M. | s2cid=23012011 | year=1986 | title=Biological extinction in earth history | journal=Science | volume = 231 | pages = 1528–1533 | doi=10.1126/science.11542058 | issue=4745 | pmid=11542058| bibcode=1986Sci...231.1528R }} 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.{{cite book | url=http://species.asu.edu/SOS_2009 | author=IISE | year=2010 | title=SOS 2009: State of Observed Species | publisher=International Institute for Species Exploration | location=Arizona State University | pages=1–8 | format=PDF | access-date=2013-09-16 | archive-date=2013-09-22 | archive-url=https://web.archive.org/web/20130922091928/http://species.asu.edu/SOS_2009 | url-status=dead }}{{cite book | url=http://species.asu.edu/SOS_2010 | author=IISE | year=2011 | title=SOS 2010: State of Observed Species | publisher=International Institute for Species Exploration | location=Arizona State University | pages=1–10 | format=PDF | access-date=2013-09-16 | archive-date=2013-09-22 | archive-url=https://web.archive.org/web/20130922093805/http://species.asu.edu/SOS_2010 | url-status=dead }}{{cite book | url=http://species.asu.edu/SOS_2011 | author=IISE | year=2012 | title=SOS 2011: State of Observed Species | publisher=International Institute for Species Exploration | location=Arizona State University | pages=1–14 | format=PDF }}{{Dead link|date=March 2022 |bot=InternetArchiveBot |fix-attempted=yes }} 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.
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Based on Chapman's (2009) report, the estimated numbers of described extant species as of 2009 can be broken down as follows:
| class="wikitable sortable" | ||||
| colspan="3" | Major/Component group | Described | Global estimate (described + undescribed) | ||
|---|---|---|---|---|
| colspan="3" | Chordates | 64,788 | ~80,500 | ||
| ↳ | colspan="2" | Mammals | 5,487 | ~5,500 | |
| ↳ | colspan="2" | Birds | 9,990 | >10,000 | |
| ↳ | colspan="2" | Reptiles | 8,734 | ~10,000 | |
| ↳ | colspan="2" | Amphibia | 6,515 | ~15,000 | |
| ↳ | colspan="2" | Fishes | 31,153 | ~40,000 | |
| ↳ | colspan="2" | Agnatha | 116 | unknown | |
| ↳ | colspan="2" | Cephalochordata | 33 | unknown | |
| ↳ | colspan="2" | Tunicata | 2,760 | unknown | |
| colspan="3" | Invertebrates | ~1,359,365 | ~6,755,830 | ||
| ↳ | colspan="2" | Hemichordata | 108 | ~110 | |
| ↳ | colspan="2" | Echinodermata | 7,003 | ~14,000 | |
| ↳ | colspan="2" | Insecta | ~1,000,000 (965,431–1,015,897) | ~5,000,000 | |
| ↳ | Archaeognatha | 470 | ||
| ↳ | Blattodea | 3,684–4,000 | ||
| ↳ | Coleoptera | 360,000–~400,000 | 1,100,000 | |
| ↳ | Dermaptera | 1,816 | ||
| ↳ | Diptera | 152,956 | 240,000 | |
| ↳ | Embioptera | 200–300 | 2,000 | |
| ↳ | Ephemeroptera | 2,500–<3,000 | ||
| ↳ | Hemiptera | 80,000–88,000 | ||
| ↳ | Hymenoptera | 115,000 | >~1,000,000{{cite journal |vauthors=Forbes et al. |title=Quantifying the unquantifiable: why Hymenoptera, not Coleoptera, is the most speciose animal order |journal=BMC Ecology |date=2018 |volume=18 |issue=1 |page=21 |doi=10.1186/s12898-018-0176-x |doi-access=free |pmid=30001194 |pmc=6042248 |bibcode=2018BMCE...18...21F }} | |
| ↳ | Isoptera | 2,600–2,800 | 4,000 | |
| ↳ | Lepidoptera | 174,250 | 300,000–500,000 | |
| ↳ | Mantodea | 2,200 | ||
| ↳ | Mecoptera | 481 | ||
| ↳ | Megaloptera | 250–300 | ||
| ↳ | Neuroptera | ~5,000 | ||
| ↳ | Notoptera | 55 | ||
| ↳ | Odonata | 6,500 | ||
| ↳ | Orthoptera | 24,380 | ||
| ↳ | Phasmatodea (Phasmida) | 2,500–3,300 | ||
| ↳ | Phthiraptera | >3,000–~3,200 | ||
| ↳ | Plecoptera | 2,274 | ||
| ↳ | Psocoptera | 3,200–~3,500 | ||
| ↳ | Siphonaptera | 2,525 | ||
| ↳ | Strepsiptera | 596 | ||
| ↳ | Thysanoptera | ~6,000 | ||
| ↳ | Trichoptera | 12,627 | ||
| ↳ | Zoraptera | 28 | ||
| ↳ | Zygentoma (Thysanura) | 370 | ||
| ↳ | colspan="2" | Arachnida | 102,248 | ~600,000 | |
| ↳ | colspan="2" | Pycnogonida | 1,340 | unknown | |
| ↳ | colspan="2" | Myriapoda | 16,072 | ~90,000 | |
| ↳ | colspan="2" | Crustacea | 47,000 | 150,000 | |
| ↳ | colspan="2" | Onychophora | 165 | ~220 | |
| ↳ | colspan="2" | non-Insect Hexapoda | 9,048 | 52,000 | |
| ↳ | colspan="2" | Mollusca | ~85,000 | ~200,000 | |
| ↳ | colspan="2" | Annelida | 16,763 | ~30,000 | |
| ↳ | colspan="2" | Nematoda | <25,000 | ~500,000 | |
| ↳ | colspan="2" | Acanthocephala | 1,150 | ~1,500 | |
| ↳ | colspan="2" | Platyhelminthes | 20,000 | ~80,000 | |
| ↳ | colspan="2" | Cnidaria | 9,795 | unknown | |
| ↳ | colspan="2" | Porifera | ~6,000 | ~18,000 | |
| ↳ | colspan="2" | Other Invertebrates | 12,673 | ~20,000 | |
| ↳ | Placozoa | 1 | - | |
| ↳ | Monoblastozoa | 1 | - | |
| ↳ | Mesozoa (Rhombozoa, Orthonectida) | 106 | - | |
| ↳ | Ctenophora | 166 | 200 | |
| ↳ | Nemertea (Nemertina) | 1,200 | 5,000–10,000 | |
| ↳ | Rotifera | 2,180 | - | |
| ↳ | Gastrotricha | 400 | - | |
| ↳ | Kinorhyncha | 130 | - | |
| ↳ | Nematomorpha | 331 | ~2,000 | |
| ↳ | Entoprocta (Kamptozoa) | 170 | 170 | |
| ↳ | Gnathostomulida | 97 | - | |
| ↳ | Priapulida | 16 | - | |
| ↳ | Loricifera | 28 | >100 | |
| ↳ | Cycliophora | 1 | - | |
| ↳ | Sipuncula | 144 | - | |
| ↳ | Echiura | 176 | - | |
| ↳ | Tardigrada | 1,045 | - | |
| ↳ | Phoronida | 10 | - | |
| ↳ | Ectoprocta (Bryozoa) | 5,700 | ~5,000 | |
| ↳ | Brachiopoda | 550 | - | |
| ↳ | Pentastomida | 100 | - | |
| ↳ | Chaetognatha | 121 | - | |
| colspan="3" | Plants sens. lat. | ~310,129 | ~390,800 | ||
| ↳ | colspan="2" | Bryophyta | 16,236 | ~22,750 | |
| ↳ | Liverworts | ~5,000 | ~7,500 | |
| ↳ | Hornworts | 236 | ~250 | |
| ↳ | Mosses | ~11,000 | ~15,000 | |
| ↳ | colspan="2" | Algae (Plant) | 12,272 | unknown | |
| ↳ | Charophyta | 2,125 | - | |
| ↳ | Chlorophyta | 4,045 | - | |
| ↳ | Glaucophyta | 5 | - | |
| ↳ | Rhodophyta | 6,097 | - | |
| ↳ | colspan="2" | Vascular Plants | 281,621 | ~368,050 | |
| ↳ | Ferns and allies | ~12,000 | ~15,000 | |
| ↳ | Gymnosperms | ~1,021 | ~1,050 | |
| ↳ | Magnoliophyta | ~268,600 | ~352,000 | |
| colspan="3" | Fungi | 98,998 (incl. Lichens 17,000) | 1,500,000 (incl. Lichens ~25,000) | ||
| colspan="3" | Others | ~66,307 | ~2,600,500 | ||
| ↳ | colspan="2" | Chromista [incl. brown algae, diatoms and other groups] | 25,044 | ~200,500 | |
| ↳ | colspan="2" | Protoctista [i.e. residual protist groups] | ~28,871 | >1,000,000 | |
| ↳ | colspan="2" | Prokaryota [ Bacteria and Archaea, excl. Cyanophyta] | 7,643 | ~1,000,000 | |
| ↳ | colspan="2" | Cyanophyta | 2,664 | unknown | |
| ↳ | colspan="2" | Viruses | 2,085 | 400,000 | |
| colspan="3" | Total (2009 data) | 1,899,587 | ~11,327,630 |
File:Species Distribution Biodiversity after Chapman 2009.png
Estimates of total number of species
However the total number of species for some taxa may be much higher.
- 10–30 million insects;{{cite web|url=http://www.si.edu/Encyclopedia_SI/nmnh/buginfo/bugnos.htm|title= Numbers of Insects (Species and Individuals) |publisher=|website = Smithsonian Institution|date = 1996}}
- 5–10 million bacteria;Proceedings of the National Academy of Sciences, Census of Marine Life (CoML) [http://news.bbc.co.uk/1/hi/sci/tech/5232928.stm BBC News]
- 1.5 million fungi;David L. Hawksworth, "The magnitude of fungal diversity: the 1•5 million species estimate revisited" Mycological Research (2001), 105: 1422-1432 Cambridge University Press [http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=95069 Abstract]
- ~1 million mites{{cite web|url=http://insects.ummz.lsa.umich.edu/ACARI/index.html|title=Acari at University of Michigan Museum of Zoology Web Page|website=insects.ummz.lsa.umich.edu}}
- ~1 million protistsPawlowski, 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].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].
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.{{cite journal|first1=Terry L.|last1=Erwin|authorlink1=Terry Erwin|title=Tropical Forests: Their Richness in Coleoptera and Other Arthropod Species|journal=The Coleopterists Bulletin|editor-last=The Coleopterists Society|volume=36|issue=1|date=March 1982|pages=74–75|issn=0010-065X|jstor=4007977}} Given the 50,000 described tropical tree species, Erwin suggested that there are almost 10 million beetle species in the tropics.{{cite book |last=Pullin|first=Andrew|year=2002|title=Conservation Biology|url=http://www.cambridge.org/us/academic/subjects/life-sciences/ecology-and-conservation/conservation-biology|location=Cambridge|publisher=Cambridge University Press|isbn= 9780521644822 |accessdate=December 24, 2013}} In 2011 a study published in PLoS Biology estimated there to be 8.7 million ± 1.3 million eukaryotic species on Earth.
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.{{cite journal |last1=Larsen |first1=Brendan B. |last2=Miller |first2=Elizabeth C. |last3=Rhodes |first3=Matthew K. |last4=Wiens |first4=John J. |title=Inordinate Fondness Multiplied and Redistributed: the Number of Species on Earth and the New Pie of Life |journal=The Quarterly Review of Biology |date=September 2017 |volume=92 |issue=3 |pages=229–265 |doi=10.1086/693564 |url=https://www.journals.uchicago.edu/doi/abs/10.1086/693564 |access-date=6 August 2023 |language=en |issn=0033-5770}} 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,{{cite web | url=https://www.nsf.gov/news/news_summ.jsp?cntn_id=138446&WT.mc_id=USNSF_51&WT.mc_ev=click |title=Researchers find that Earth may be home to 1 trillion species | work=NSF | date=2 May 2016| accessdate=6 May 2016}}{{cite journal |last1=Locey, Lennon |title=Scaling laws predict global microbial diversity |journal=Proceedings of the National Academy of Sciences of the United States of America |year=2016 |volume=113 |issue=21 |pages=5970–5975 |doi=10.1073/pnas.1521291113 |pmid=27140646 |pmc=4889364 |bibcode=2016PNAS..113.5970L |doi-access=free }} 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.{{cite journal |last1=Louca |first1=Stilianos |last2=Mazel |first2=Florent |last3=Doebeli |first3=Michael |last4=Parfrey |first4=Laura Wegener |title=A census-based estimate of Earth's bacterial and archaeal diversity |journal=PLOS Biology |date=4 February 2019 |volume=17 |issue=2 |pages=e3000106 |doi=10.1371/journal.pbio.3000106 |pmid=30716065 |language=en |issn=1545-7885|pmc=6361415 |doi-access=free }}
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.{{cite web |title=Indicators and Assessments Unit |url=http://www.zsl.org/science/research-projects/indicators-assessments/index,134,ZI.html |publisher=Zoological Society of London}} 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.{{cite web |title=Trends in the status of biodiversity |url=http://www.iucnredlist.org/about/summary-statistics |accessdate=25 November 2013 |publisher=IUCN}} 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.{{cite web |title=Global Wild Bird Index |url=http://www.bipindicators.net/wbi |url-status=dead |archive-url=https://web.archive.org/web/20131202225749/http://www.bipindicators.net/wbi |archive-date=2013-12-02 |access-date=2013-11-25 |publisher=Biodiversity Indicators Partnership}} 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.
Biodiversity loss
{{Excerpt|biodiversity loss}}
See also
{{portal|Ecology|Environment|World}}
References
External links
- [http://www.biodiversitya-z.com/ Biodiversity A-Z] {{Webarchive|url=https://web.archive.org/web/20200919061622/http://www.biodiversitya-z.com/ |date=2020-09-19 }}
- [http://species.wikimedia.org/ Wikispecies]
- [http://www.globalissues.org/EnvIssues/Biodiversity.asp Biodiversity—Global issues]