Holocene extinction

The Holocene extinction, or Anthropocene extinction,^[3][4] is the ongoing extinction event caused by humans during the Holocene epoch. These extinctions span numerous families of plants^[5][6][7] and animals, including mammals, birds, reptiles, amphibians, fish, and invertebrates, and affecting not just terrestrial species but also large sectors of marine life.^[8] With widespread degradation of biodiversity hotspots, such as coral reefs and rainforests, as well as other areas, the vast majority of these extinctions are thought to be undocumented, as the species are undiscovered at the time of their extinction, which goes unrecorded. The current rate of extinction of species is estimated at 100 to 1,000 times higher than natural background extinction rates^{[9][10][11][12][13]} and is increasing.^[14] During the past 100–200 years, biodiversity loss and species extinction have accelerated,^[10] to the point that most conservation biologists now believe that human activity has either produced a period of mass extinction,^[15][16] or is on the cusp of doing so.^[17][18] As such, after the "Big Five" mass extinctions, the Holocene extinction event has also been referred to as the sixth mass extinction or sixth extinction;^[19][20][21] given the recent recognition of the Capitanian mass extinction, the term seventh mass extinction has also been proposed for the Holocene extinction event.^[22][23]

The Holocene extinction follows the extinction of the majority of large (megafaunal) animals during the preceding Late Pleistocene. Some of these extinctions were likely in part due to human hunting pressure.^[24][25] The most popular theory is that human overhunting of species added to existing stress conditions as the Holocene extinction coincides with human colonization of many new areas around the world. Although there is debate regarding how much human predation and habitat loss affected their decline, certain population declines have been directly correlated with the onset of human activity, such as the extinction events of New Zealand, Madagascar, and Hawaii. Aside from humans, climate change may have been a driving factor in the megafaunal extinctions, especially at the end of the Pleistocene.

Over the course of the Late Holocene, there were hundreds of extinctions of birds on islands across the Pacific, driven by human settlement of the previously uninhabited islands, with extinctions peaking around 1300 AD.^[26] Roughly 12% of avian species have been driven to extinction by human activity over the last 126,000 years, which is double previous estimates.^[27]

In the twentieth century, human numbers quadrupled, and the size of the global economy increased twenty-five-fold.^[28][29] This Great Acceleration or Anthropocene epoch has also accelerated species extinction.^[30][31] Ecologically, humanity is now an unprecedented "global superpredator",^[32] which consistently preys on the adults of other apex predators, takes over other species' essential habitats and displaces them,^[33] and has worldwide effects on food webs.^[34] There are many famous examples of extinctions within Africa, Asia, Europe, Australia, North and South America, and on smaller islands.

Overall, the Holocene extinction can be linked to the human impact on the environment. The Holocene extinction continues into the 21st century, with anthropogenic global warming, human population growth,^{[35][36][37][38]} increasing per capita consumption^[10][39] (especially by the super-affluent),^[40][41][42] and meat production and consumption,^{[43][44][45][46][47][48]} among others, being the primary drivers of mass extinction. Deforestation,^[43] overfishing, ocean acidification, the destruction of wetlands,^[49] and the decline in amphibian populations,^[50] among others, are a few broader examples of global biodiversity loss.