Holocene extinction

The Holocene or Anthropocene extinction is an ongoing extinction event caused by human activity during the current geological epoch, impacting diverse families of plants and animals, including mammals, birds, reptiles, amphibians, fish, and invertebrates, as well as both terrestrial and marine species. It is sometimes also called the sixth extinction (though this can also describe the Capitanian). Current extinction rates are estimated at 100 to 1,000 times higher than natural background extinction rates. The Holocene extinction was preceded by the Late Pleistocene extinctions at the end of the last ice age (to which human activity also likely contributed) and the extinctions caused by Polynesian expansion. The Holocene extinction continues into the 21st century, driven by anthropogenic climate change, destruction of wetlands, deforestation, overfishing, ocean acidification, human population growth, economic growth, and increasing consumption, particularly among affluent societies. Factors such as rising meat production and the destruction of critical habitats compound these issues. Other drivers include overexploitation of natural resources, pollution, and climate change-induced shifts in ecosystems. Major extinction events during this period have been recorded across all continents, including Africa, Asia, Europe, Australia, North and South America, and various islands.

Overview

Mass extinctions are characterized by the loss of at least 75% of species within a geologically short period of time (i.e., less than 2 million years). The Holocene is the current geological epoch. The precise timing of the Holocene extinction event remains debated, with no clear consensus on when it began or whether it should be considered distinct from the Quaternary extinction event. However, most scientists agree that human activities are the primary driver of the Holocene extinction. A 1998 survey conducted by the American Museum of Natural History found that 70% of biologists acknowledged an ongoing anthropogenic extinction event. Some researchers suggested that the activities of earlier archaic humans may have contributed to earlier extinctions, especially in Australia, New Zealand, and Madagascar. Even modest hunting pressure, combined with the vulnerability of large animals on isolated islands, is thought to have been enough to wipe out entire species. Only in the more recent stages of the Holocene have plants suffered extensive losses, which are also linked to human activities such as deforestation and land conversion.

Extinction rate The contemporary rate of extinction is estimated at 100 to 1,000 times higher than the natural background extinction rate—the typical rate of species loss through natural evolutionary processes. One estimation suggested the rate could be as high as 10,000 times the background extinction rate, though this figure remains controversial. Theoretical ecologist Stuart Pimm has noted that the extinction rate for plants alone is 100 times higher than normal. While some argue that the current extinction rates have not yet reached the catastrophic levels of past mass extinctions, Barnosky et al. (2011) and Hull et al. (2015) points out that extinction rates during past mass extinctions cannot be fully determined because of gaps in the fossil record. The former acknowledge that "the recent loss of species is dramatic and serious" but it does not "yet qualify as a mass extinction in the palaeontological sense of the Big Five". Estimates of species lost per year vary widely—from 1.5 to 40,000 species—but all indicate that human activity is driving this crisis. In The Future of Life (2002), biologist Edward Osborne Wilson predicted that, if current trend continues, half of Earth's higher lifeforms could be extinct by 2100. More recent studies further support this view. A 2015 study on Hawaiian snails suggested that up to 7% of Earth's species may already be extinct. A 2021 study also found that only around 3% of the planet's terrestrial surface remains ecologically and faunally intact—areas that still have healthy populations of native species and minimal human footprint. A 2022 study suggests that if global warming continues, between 13% and 27% of terrestrial vertebrate species could be driven to extinction by 2100, with habitat destructions and co-extinctions accounting for the rest. The 2019 Global Assessment Report on Biodiversity and Ecosystem Services, published by the United Nations IPBES, estimated that about one million species are currently at risk of extinction within decades because of human activities. Organized human existence is jeopardised by increasingly rapid destruction of the systems that support life on Earth, according to the report, the result of one of the most comprehensive studies of the health of the planet ever conducted. Moreover, the 2021 Economics of Biodiversity review, published by the UK government, asserts that "biodiversity is declining faster than at any time in human history." According to a 2022 study published in Frontiers in Ecology and the Environment, a survey of more than 3,000 experts says that the extent of the mass extinction might be greater than previously thought, and estimates that roughly 30% of species "have been globally threatened or driven extinct since the year 1500". In a 2022 report, IPBES listed unsustainable fishing, hunting, and logging as some of the primary drivers of the global extinction crisis. A 2023 study published in PLOS One shows that around two million species are threatened with extinction, double the estimate put forward in the 2019 IPBES report. According to a 2023 study published in PNAS, at least 73 genera of animals have gone extinct since 1500. If humans had never existed, the study estimates it would have taken 18,000 years for the same genera to have disappeared naturally, leading the authors to conclude that "the current generic extinction rates are 35 times higher than expected background rates prevailing in the last million years under the absence of human impacts" and that human civilization is causing the "rapid mutilation of the tree of life".

Attribution

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