The Holocene extinction, otherwise referred to as the Sixth extinction or Anthropocene extinction, is the ongoing extinction event of species during the present Holocene epoch, mainly as a result of human activity.
| “ | For the first time since the demise of the dinosaurs 65 million years ago, we face a global mass extinction of wildlife. We ignore the decline of other species at our peril – for they are the barometer that reveals our impact on the world that sustains us. | ” |
| — Mike Barrett, director of science and policy at WWF's UK branch[139] | ||
Recent extinction[edit]
Recent extinctions are more directly attributable to human influences, whereas prehistoric extinctions can be attributed to other factors, such as global climate change.[11][12] The International Union for Conservation of Nature (IUCN) characterises 'recent' extinction as those that have occurred past the cut-off point of 1500,[140] and at least 875 species have gone extinct since that time and 2012.[141] Some species, such as the Père David's deer[142] and the Hawaiian crow,[143] are extinct in the wild, and survive solely in captive populations. Other species, such as the Florida panther, are ecologically extinct, surviving in such low numbers that they essentially have no impact on the ecosystem.[144]:318 Other populations are only locally extinct (extirpated), still existence elsewhere, but reduced in distribution,[144]:75–77 as with the extinction of gray whales in the Atlantic,[145] and of the leatherback sea turtle in Malaysia.[146]
Habitat destruction[edit]
Global warming is widely accepted as being a contributor to extinction worldwide, in a similar way that previous extinction events have generally included a rapid change in global climate and meteorology. It is also expected to disrupt sex ratios in many reptiles which have temperature-dependent sex determination.
The removal of land to clear way for palm oil plantations releases carbon emissions held in the peatlands of Indonesia.[148][149] Palm oil mainly serves as a cheap cooking oil,[150] and also as a (controversial) biofuel. However, damage to peatland contributes to 4% of global greenhouse gas emissions, and 8% of those caused by burning fossil fuels.[151] Palm oil cultivation has also been criticized for other impacts to the environment,[152][153] including deforestation,[154] which has threatened critically endangered species such as the orangutan[155][156] and the tree-kangaroo.[157] The IUCN stated in 2016 that the species could go extinct within a decade if measures are not taken to preserve the rainforests in which they live.[158]
Some scientists and academics assert that industrial agriculture and the growing demand for meat is contributing to significant global biodiversity lossas this is a significant driver of deforestation and habitat destruction; species-rich habitats, such as significant portions of the Amazon region, are being converted to agriculture for meat production.[13][159][160][161][162] A 2017 study by the World Wildlife Fund (WWF) found that 60% of biodiversity loss can be attributed to the vast scale of feed crop cultivation required to rear tens of billions of farm animals.[163] Moreover, a 2006 report by the Food and Agriculture Organization (FAO) of the United Nations, Livestock's Long Shadow, also found that the livestock sector is a "leading player" in biodiversity loss.[164]
Rising levels of carbon dioxide are resulting in influx of this gas into the ocean, increasing its acidity. Marine organisms which possess calcium carbonate shells or exoskeletons experience physiological pressure as the carbonate reacts with acid. For example, this is already resulting in coral bleaching on various coral reefs worldwide, which provide valuable habitat and maintain a high biodiversity. Marine gastropods, bivalves and other invertebrates are also affected, as are the organisms that feed on them.[citation needed] According to a 2018 study published in Science, global Orca populations are poised to collapse due to toxic chemical and PCB pollution. PCBs are still leaking into the sea in spite of being banned for decades.[165]
Some researchers suggest that by 2050 there could be more plastic than fish in the oceans by weight,[40] with about 8,800,000 metric tons (9,700,000 short tons) of plastic being discharged into the oceans annually.[166] Single-use plastics, such as plastic shopping bags, make up the bulk of this, and can often be ingested by marine life, such as with sea turtles.[167] These plastics can degrade into microplastics, smaller particles that can affect a larger array of species. Microplastics make up the bulk of the Great Pacific Garbage Patch, and their smaller size is detrimental to cleanup efforts.[168]
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