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Do you have a source for your claims? This disagrees with you:<br />
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Humans: Cause Of Extinction Of Nearly 500 Species Since 1900
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<div class="contentRow-snippet js-unfurl-desc">An international team of researchers led by the National Autonomous University in Mexico discovered that since 1900, around 477 different species have died off as a consequence of human activity. This rate is 100 times faster compared to the natural rate of extinction.</div>
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Yes, Ceballos et al 2015 and 2017 are actually the studies that use the SAR metric and get referenced the most by media in support of the "mass extinction" idea. Well, there is another infamous etymology study with fundamental flaws that people love to quote as well because supports the narrative.<br />
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When assessing Ceballos two bodies of work, you'll note a few things.<br />
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* The background rate is estimated using the E/MSY found in Pimms 1995. The problem with this is that the formula doesn't account for species average longevity, thus interspecies comparisons will always be biased against species that have been on earth for lesser time - mammals obviously being much lower time scales than other past species. <br />
* Barnosky et al 2011 and MacLeod 2013 note an adjusted estimate of approximately 0.5 extinctions per year in the Pleistocene. Using this range as a reference point, contrasted with the UICN Red List 2014 of recorded extinctions, we see a noted 338 terrestrial vertebrate species since 1500. A background rate of 0.5 per year would suggest 250 extinctions naturally, without human interventions. <br />
* We are now looking at a remaining 88 terrestrial vertebrate species that can be attributed as being directly caused by anthropogenic fingerprinting. Loehle and Essenbach 2012 noted that of those 500 years of extinctions, over 95% are noted to be genetically isolated island dwelling species. Only 6/128 documented bird species, and 3/61 mammalian species are noted as being continental inhabitants. Note this study includes Australia as a genetically isolated island.<br />
* Using vertebrates as a surrogate for extant species biodiversity presents another critical problem. The majority of the earths biomass is made up of insect species, who are far less documented. Of the estimated 2.6-7.8 million insect species, about 30,000 are documented as per Stork et al 2015. <br />
* Of these 30,000, the vast majority are of 4 main groups, butterflies, tiger beetles, damselfly, dragonfly. 66 extinctions have been documented, although the data is quite deficient in this group. Even if we extrapolate the rates of vertebrates noted above to insects, we come to a figure of about 1.5 species per year, which is consistent with Coope 2014 who has noted a distinct lack of Pleistocene insect extinction.<br />
* Ceballos fully ignores the biodiversity gains via speciation and new species discovery. MacLeod 2013, Sax and Gaines 2008, Ellis, Antil and Kreft 2012, De Vos et al 2014 and Dornelas et al 2014 all note gains in biodiversity over contemporary time scales, which are ignored by Ceballos. Dornelas 2014 in particular notes no net loss in biodiversity over substantial tropical regions throughout the late 1900s. <br />
* Even if we were to ignore all the issues with the Ceballos study as a conclusion of a mass extinction event, the rate evidenced in the study is not even remotely close to the rates of extinction during past mass extinctions. Even at the accelerated rates projected by Ceballos and Payne 2014, it would take almost 40,000 years to reach the tipping points that were seen during the least severe mass extinction events of the past(Briggs 2017).</div>
