Editing Biodiversity (section)

===Diversification===
The existence of a ''global [[carrying capacity]]'', limiting the amount of life that can live at once, is debated, as is the question of whether such a limit would also cap the number of species. While records of life in the sea show a [[logistic function|logistic]] pattern of growth, life on land (insects, plants and tetrapods) shows an [[exponential growth|exponential]] rise in diversity.<ref name="Sahney, S. 2010" /> As one author states, "Tetrapods have not yet invaded 64 percent of potentially habitable modes and it could be that without human influence the ecological and [[Taxonomy (biology)|taxonomic]] diversity of tetrapods would continue to increase exponentially until most or all of the available eco-space is filled."<ref name="Sahney, S. 2010" />

It also appears that the diversity continues to increase over time, especially after mass extinctions.<ref>{{cite web|url=https://biox.stanford.edu/highlight/stanford-researchers-discover-animal-functional-diversity-started-out-poor-became-richer|title=Stanford researchers discover that animal functional diversity started poor, became richer over time |website=biox.stanford.edu|date=11 March 2015 }}</ref>

On the other hand, changes through the [[Phanerozoic]] correlate much better with the [[Hyperbolic growth|hyperbolic]] model (widely used in [[population biology]], [[demography]] and [[macrosociology]], as well as [[fossil]] biodiversity) than with exponential and logistic models. The latter models imply that changes in diversity are guided by a first-order [[positive feedback]] (more ancestors, more descendants) and/or a [[negative feedback]] arising from resource limitation. Hyperbolic model implies a second-order positive feedback.<ref name="Hautmann et al. 2015" /> Differences in the strength of the second-order feedback due to different intensities of interspecific competition might explain the faster rediversification of [[ammonoids]] in comparison to [[bivalves]] after the [[end-Permian extinction]].<ref name="Hautmann et al. 2015">{{cite journal |last1=Hautmann |first1=Michael |last2=Bagherpour |first2=Borhan |last3=Brosse |first3=Morgane |last4=Frisk |first4=Åsa |last5=Hofmann |first5=Richard |last6=Baud |first6=Aymon |last7=Nützel |first7=Alexander |last8=Goudemand |first8=Nicolas |last9=Bucher |first9=Hugo |last10=Brayard |first10=Arnaud |title=Competition in slow motion: the unusual case of benthic marine communities in the wake of the end-Permian mass extinction |journal=Palaeontology |date=2015 |volume=58 |issue=5 |pages=871–901 |doi=10.1111/pala.12186 |bibcode=2015Palgy..58..871H |doi-access=free }}</ref> The hyperbolic pattern of the [[world population]] growth arises from a second-order positive feedback between the population size and the rate of technological growth.<ref name="pmid18677962">{{cite journal | pmid = 18677962 | year = 2008 | last1 = Markov | first1 = AV | last2 = Korotaev | first2 = AV | title = Hyperbolic growth of marine and continental biodiversity through the phanerozoic and community evolution | volume = 69 | issue = 3 | pages = 175–194 | journal = Journal of General Biology | url=http://elementy.ru/genbio/abstracts?artid=177}}</ref> The hyperbolic character of biodiversity growth can be similarly accounted for by a feedback between diversity and community structure complexity.<ref name="pmid18677962" /><ref name="Markov-2007" /> The similarity between the curves of biodiversity and human population probably comes from the fact that both are derived from the interference of the hyperbolic trend with cyclical and [[stochastic]] dynamics.<ref name="pmid18677962" /><ref name="Markov-2007">
{{cite journal | doi=10.1016/j.palwor.2007.01.002 | title=Phanerozoic marine biodiversity follows a hyperbolic trend | year=2007 | last1=Markov | first1=A | last2=Korotayev | first2=A | journal=[[Palaeoworld]] | volume=16 | issue=4 | pages=311–318 }}</ref>

Most biologists agree however that the period since human emergence is part of a new mass extinction, named the [[Holocene extinction event]], caused primarily by the impact humans are having on the environment.<ref>[http://www.amnh.org/museum/press/feature/biofact.html National Survey Reveals Biodiversity Crisis] {{webarchive|url=https://web.archive.org/web/20070607101209/http://www.amnh.org/museum/press/feature/biofact.html |date=7 June 2007 }} American Museum of Natural History</ref> It has been argued that the present rate of extinction is sufficient to eliminate most species on the planet Earth within 100 years.<ref name="Wilson2002">{{cite book|first=Edward O. |last=Wilson|title=The Future of Life|url={{google books |plainurl=y |id=Guosshxltn4C}}|date=1 January 2002|publisher=Alfred A. Knopf|isbn=978-0-679-45078-8}}</ref>

New species are regularly discovered (on average between 5–10,000 new species each year, most of them [[insect]]s) and many, though discovered, are not yet classified (estimates are that nearly 90% of all [[arthropod]]s are not yet classified).<ref name="heywood" /> Most of the terrestrial diversity is found in [[tropical forest]]s and in general, the land has more species than the ocean; some 8.7&nbsp;million species may exist on Earth, of which some 2.1&nbsp;million live in the ocean.<ref name="Moraplos" />