During the past 100–200 years, biodiversity loss and species extinction have accelerated
humankind has either entered a period of mass extinction, or is on the cusp of doing so. As such, the event has also been referred to as the sixth mass extinction or sixth extinction.
The Holocene extinction includes the disappearance of large land animals known as
The contemporary rate of extinction of species is estimated at 100 to 1,000 times higher than the
Theoretical ecologist Stuart Pimm stated that the extinction rate for plants is 100 times higher than normal.
Some contend that contemporary extinction has yet to reach the level of the previous five mass extinctions, and that this comparison downplays how severe the first five mass extinctions were. John Briggs argues that there is inadequate data to determine the real rate of extinctions, and shows that estimates of current species extinctions varies enormously, ranging from 1.5 species to 40,000 species going extinct due to human activities each year. Both papers from Barnosky et al. (2011) and Hull et al. (2015) point out that the real rate of extinction during previous mass extinctions is unknown, both as only some organisms leave fossil remains, and as the temporal resolution of the fossil layer is larger than the time frame of the extinction events. However, all these authors agree that there is a modern biodiversity crisis with population declines affecting numerous species, and that a future anthropogenic mass extinction event is a big risk. The 2011 study by Barnosky et al. confirms that "current extinction rates are higher than would be expected from the fossil record" and adds that anthropogenic ecological stressors, including climate change, habitat fragmentation, pollution, overfishing, overhunting, invasive species and expanding human biomass will intensify and accelerate extinction rates in the future without significant mitigation efforts.
In The Future of Life (2002),
Edward Osborne Wilson of Harvard calculated that, if the current rate of human disruption of the biosphere continues, one-half of Earth's higher lifeforms will be extinct by 2100. A 1998 poll conducted by the American Museum of Natural History found that 70% of biologists acknowledge an ongoing anthropogenic extinction event.
In a pair of studies published in 2015, extrapolation from observed extinction of Hawaiian snails led to the conclusion that 7% of all species on Earth may have been lost already. A 2021 study published in the journal Frontiers in Forests and Global Change found that only around 3% of the planet's terrestrial surface is ecologically and faunally intact, meaning areas with healthy populations of native animal species and little to no human footprint.
There is widespread consensus among scientists that human activity is accelerating the extinction of many animal species through the destruction of habitats, the consumption of animals as resources, and the elimination of species that humans view as threats or competitors. That humans have become the primary driver of modern extinctions is undeniable, rising extinction trends impacting numerous animal groups including mammals, birds, reptiles, and amphibians have prompted scientists to declare a biodiversity crisis.
Characterisation of recent extinction as a mass extinction has been debated among scientists.
overconsumption, population growth and intensive farming, which is further evidence that humans have unleashed a sixth mass extinction event; however, this finding has been disputed by one 2020 study, which posits that this major decline was primarily driven by a few extreme outlier populations, and that when these outliers are removed, the trend shifts to that of a decline between the 1980s and 2000s, but a roughly positive trend after 2000. A 2021 report in Frontiers in Conservation Science which cites both of the aforementioned studies, says "population sizes of vertebrate species that have been monitored across years have declined by an average of 68% over the last five decades, with certain population clusters in extreme decline, thus presaging the imminent extinction of their species," and asserts "that we are already on the path of a sixth major extinction is now scientifically undeniable." A 2022 study published in Biological Reviews builds upon previous studies documenting biodiversity decline to assert that a sixth mass extinction event caused by anthropogenic activity is currently underway.
, The Next Frontier: Human Development and the Anthropocene:
The planet's biodiversity is plunging, with a quarter of species facing extinction, many within decades. Numerous experts believe we are living through, or on the cusp of, a mass species extinction event, the sixth in the history of the planet and the first to be caused by a single organism—us.
The 2022 Living Planet Report found that vertebrate wildlife populations have plummeted by an average of almost 70% since 1970, with agriculture and fishing being the primary drivers of this decline.
Some scientists, including Rodolfo Dirzo and Paul R. Ehrlich, contend that the sixth mass extinction is largely unknown to most people globally, and is also misunderstood by many in the scientific community. They say it is not the disappearance of species, which gets the most attention, that is at the heart of the crisis, but "the existential threat of myriad population extinctions."
The abundance of species extinctions considered anthropogenic, or due to human activity, has sometimes (especially when referring to hypothesized future events) been collectively called the "Anthropocene extinction".Anthropocene is a term introduced in 2000. Some now postulate that a new geological epoch has begun, with the most abrupt and widespread extinction of species since the Cretaceous–Paleogene extinction event 66 million years ago.
The term "anthropocene" is being used more frequently by scientists, and some commentators may refer to the current and projected future extinctions as part of a longer Holocene extinction.
and also say that "[f]ormal adoption of this term in the near future will largely depend on its utility, particularly to earth scientists working on late Holocene successions."
It has been suggested that human activity has made the period starting from the mid-20th century different enough from the rest of the Holocene to consider it a new
geological epoch, known as the Anthropocene, a term which was considered for inclusion in the timeline of Earth's history by the International Commission on Stratigraphy in 2016. In order to constitute the Holocene as an extinction event, scientists must determine exactly when anthropogenic greenhouse gas emissions began to measurably alter natural atmospheric levels on a global scale, and when these alterations caused changes to global climate. Using chemical proxies from Antarctic ice cores, researchers have estimated the fluctuations of carbon dioxide (CO2) and methane (CH4) gases in the Earth's atmosphere during the late Pleistocene and Holocene epochs. Estimates of the fluctuations of these two gases in the atmosphere, using chemical proxies from Antarctic ice cores, generally indicate that the peak of the Anthropocene occurred within the previous two centuries: typically beginning with the Industrial Revolution, when the highest greenhouse gas levels were recorded.
PNAS found that since the dawn of human civilization, the biomass of wild mammals has decreased by 83%. The biomass decrease is 80% for marine mammals, 50% for plants and 15% for fish. Currently, livestock make up 60% of the biomass of all mammals on earth, followed by humans (36%) and wild mammals (4%). As for birds, 70% are domesticated, such as poultry, whereas only 30% are wild.
on different land masses over time, with the arrival of humans indicated.
Extinction of animals, plants, and other organisms caused by human actions may go as far back as the late Pleistocene, over 12,000 years ago. There is a correlation between megafaunal extinction and the arrival of humans. Over the past 125,000 years, the average body size of wildlife has fallen by 14% as human actions eradicated megafauna on all continents with the exception of Africa.
Human civilization was founded on and grew from agriculture. The more land used for farming, the greater the population a civilization could sustain, and subsequent popularization of farming led to habitat conversion.
Habitat destruction by humans, thus replacing the original local ecosystems, is a major driver of extinction. The sustained conversion of biodiversity rich forests and wetlands into poorer fields and pastures (of lesser carrying capacity for wild species), over the last 10,000 years, has considerably reduced the Earth's carrying capacity for wild birds, among other organisms, in both population size and species count.
Other, related human causes of the extinction event include
infectious diseases spread through livestock and crops.
Agriculture and climate change
Recent investigations into the practice of landscape burning during the Neolithic Revolution has a major implication for the current debate about the timing of the Anthropocene and the role that humans may have played in the production of greenhouse gases prior to the Industrial Revolution. Studies of early hunter-gatherers raise questions about the current use of population size or density as a proxy for the amount of land clearance and anthropogenic burning that took place in pre-industrial times. Scientists have questioned the correlation between population size and early territorial alterations. Ruddiman and Ellis' research paper in 2009 makes the case that early farmers involved in systems of agriculture used more land per capita than growers later in the Holocene, who intensified their labor to produce more food per unit of area (thus, per laborer); arguing that agricultural involvement in rice production implemented thousands of years ago by relatively small populations have created significant environmental impacts through large-scale means of deforestation.
While a number of human-derived factors are recognized as contributing to rising atmospheric concentrations of CH4 (methane) and CO2 (carbon dioxide), deforestation and territorial clearance practices associated with agricultural development may be contributing most to these concentrations globally. Scientists that are employing a variance of archaeological and paleoecological data argue that the processes contributing to substantial human modification of the environment spanned many thousands of years on a global scale and thus, not originating as late as the Industrial Revolution. Gaining popularity on his uncommon hypothesis, palaeoclimatologist William Ruddiman in 2003, has argued that in the early Holocene 11,000 years ago, atmospheric carbon dioxide and methane levels fluctuated in a pattern which was different from the Pleistocene epoch before it. He argued that the patterns of the significant decline of CO2 levels during the last ice age of the Pleistocene inversely correlates to the Holocene where there have been dramatic increases of CO2 around 8000 years ago and CH4 levels 3000 years after that. The correlation between the decrease of CO2 in the Pleistocene and the increase of it during the Holocene implies that the causation of this spark of greenhouse gases into the atmosphere was the growth of human agriculture during the Holocene such as the anthropogenic expansion of (human) land use and irrigation.
Atlantic Period, warm and wetBottom: Potential vegetation in climate now if not for human effects like agriculture.
One of the main theories for the extinction's cause is
A 2020 study published in Science Advances found that human population size and/or specific human activities, not climate change, caused rapidly rising global mammal extinction rates during the past 126,000 years. Around 96% of all mammalian extinctions over this time period are attributable to human impacts. According to Tobias Andermann, lead author of the study, "these extinctions did not happen continuously and at constant pace. Instead, bursts of extinctions are detected across different continents at times when humans first reached them. More recently, the magnitude of human driven extinctions has picked up the pace again, this time on a global scale."
Megafauna play a significant role in the lateral transport of mineral nutrients in an ecosystem, tending to translocate them from areas of high to those of lower abundance. They do so by their movement between the time they consume the nutrient and the time they release it through elimination (or, to a much lesser extent, through decomposition after death).
modern humans; some recent studies favor this theory.
Large populations of megaherbivores have the potential to contribute greatly to the atmospheric concentration of
sauropods could have emitted 520 million tons of methane to the atmosphere annually, contributing to the warmer climate of the time (up to 10 °C warmer than at present). This large emission follows from the enormous estimated biomass of sauropods, and because methane production of individual herbivores is believed to be almost proportional to their mass.
Recent studies have indicated that the extinction of megafaunal herbivores may have caused a reduction in
Pleistocene epoch after the extinction of megafauna in the Americas. After early humans migrated to the Americas about 13,000 BP, their hunting and other associated ecological impacts led to the extinction of many megafaunal species there. Calculations suggest that this extinction decreased methane production by about 9.6 million tons per year. This suggests that the absence of megafaunal methane emissions may have contributed to the abrupt climatic cooling at the onset of the Younger Dryas. The decrease in atmospheric methane that occurred at that time, as recorded in ice cores, was 2–4 times more rapid than any other decrease in the last half million years, suggesting that an unusual mechanism was at work.
The hyperdisease hypothesis, proposed by Ross MacPhee in 1997, states that the megafaunal die-off was due to an indirect transmission of diseases by newly arriving humans.
gestation period and a higher population size. Humans are thought to be the sole cause as other earlier migrations of animals into North America from Eurasia did not cause extinctions.
There are many problems with this theory, as this disease would have to meet several criteria: it has to be able to sustain itself in an environment with no hosts; it has to have a high infection rate; and be extremely lethal, with a mortality rate of 50–75%. Disease has to be very virulent to kill off all the individuals in a species, and even such a virulent disease as West Nile fever is unlikely to have caused extinction.
However, diseases have been the cause for some extinctions. The introduction of
mountain gorillas remaining. 60% of primate species face an anthropogenically driven extinction crisis and 75% have declining populations.
consumption growth, prominently in the past two centuries, are regarded as the underlying causes of extinction.
The loss of animal species from ecological communities, defaunation, is primarily driven by human activity. This has resulted in empty forests, ecological communities depleted of large vertebrates. This is not to be confused with extinction, as it includes both the disappearance of species and declines in abundance. Defaunation effects were first implied at the Symposium of Plant-Animal Interactions at the University of Campinas, Brazil in 1988 in the context of Neotropical forests. Since then, the term has gained broader usage in conservation biology as a global phenomenon.
Some scholars assert that the emergence of
CUNY professor David Harvey, for example, posits that the neoliberal era "happens to be the era of the fastest mass extinction of species in the Earth's recent history". Major lobbying organizations representing corporations in the agriculture, fisheries, forestry and paper, mining, and oil and gas industries, including the United States Chamber of Commerce, have been pushing back against legislation that could address the extinction crisis. A 2022 report by the climate think tank InfluenceMap stated that "although industry associations, especially in the US, appear reluctant to discuss the biodiversity crisis, they are clearly engaged on a wide range of policies with significant impacts on biodiversity loss."
tigers are down to 3,000 in the wild, from 50,000. A December 2016 study by the Zoological Society of London, Panthera Corporation and Wildlife Conservation Society showed that cheetahs are far closer to extinction than previously thought, with only 7,100 remaining in the wild, existing within only 9% of their historic range. Human pressures are to blame for the cheetah population crash, including prey loss due to overhunting by people, retaliatory killing from farmers, habitat loss and the illegal wildlife trade.
We are seeing the effects of 7 billion people on the planet. At present rates, we will lose the big cats in 10 to 15 years.
Sussex University stated that their study suggested that humans are making large parts of the planet uninhabitable for wildlife. Goulson characterized the situation as an approaching "ecological Armageddon", adding that "if we lose the insects then everything is going to collapse." A 2019 study found that over 40% of insect species are threatened with extinction. The most significant drivers in the decline of insect populations are associated with intensive farming practices, along with pesticide use and climate change. The world's insect population decreases by around 1 to 2 per cent per year.
We have driven the rate of biological extinction, the permanent loss of species, up several hundred times beyond its historical levels, and are threatened with the loss of a majority of all species by the end of the 21st century.
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
List of critically endangered species
Share of species threatened with extinction as of 2019.
Humans are rapidly driving the largest vertebrate animals towards extinction, and in the process interrupting a 66-million-year-old feature of ecosystems, the relationship between diet and body mass, which researchers suggest could have unpredictable consequences. A 2019 study published in Nature Communications found that rapid biodiversity loss is impacting larger mammals and birds to a much greater extent than smaller ones, with the body mass of such animals expected to shrink by 25% over the next century. Another 2019 study published in Biology Letters found that extinction rates are perhaps much higher than previously estimated, in particular for bird species.
The 2019 Global Assessment Report on Biodiversity and Ecosystem Services lists the primary causes of contemporary extinctions in descending order: (1) changes in land and sea use (primarily agriculture and overfishing respectively); (2) direct exploitation of organisms such as hunting; (3) anthropogenic climate change; (4) pollution and (5) invasive alien species spread by human trade. This report, along with the 2020 Living Planet Report by the WWF, both project that climate change will be the leading cause in the next several decades.
A June 2020 study published in
PNAS posits that the contemporary extinction crisis "may be the most serious environmental threat to the persistence of civilization, because it is irreversible" and that its acceleration "is certain because of the still fast growth in human numbers and consumption rates." The study found that more than 500 vertebrate species are poised to be lost in the next two decades.
silphium and the passenger pigeon. It was estimated in 2012 that 13 percent of Earth's ice-free land surface is used as row-crop agricultural sites, 26 percent used as pastures, and 4 percent urban-industrial areas.
In March 2019, Nature Climate Change published a study by ecologists from Yale University, who found that over the next half century, human land use will reduce the habitats of 1,700 species by up to 50%, pushing them closer to extinction. That same month PLOS Biology published a similar study drawing on work at the University of Queensland, which found that "more than 1,200 species globally face threats to their survival in more than 90% of their habitat and will almost certainly face extinction without conservation intervention".
Since 1970, the populations of migratory freshwater fish have declined by 76%, according to research published by the Zoological Society of London in July 2020. Overall, around one in three freshwater fish species are threatened with extinction due to human-driven habitat degradation and overfishing.
IPBES Global Assessment Report on Biodiversity and Ecosystem Services attributed much of this ecological destruction to agriculture and fishing, with the meat and dairy industries having a very significant impact. Since the 1970s food production has soared in order to feed a growing human population and bolster economic growth, but at a huge price to the environment and other species. The report says some 25% of the earth's ice-free land is used for cattle grazing. A 2020 study published in Nature Communications warned that human impacts from housing, industrial agriculture and in particular meat consumption are wiping out a combined 50 billion years of earth's evolutionary history (defined as phylogenetic diversity[a]) and driving to extinction some of the "most unique animals on the planet," among them the Aye-aye lemur, the Chinese crocodile lizard and the pangolin.
Said lead author Rikki Gumbs:
We know from all the data we have for threatened species, that the biggest threats are agriculture expansion and the global demand for meat. Pasture land, and the clearing of rainforests for production of soy, for me, are the largest drivers – and the direct consumption of animals.
The vaquita, the world's most endangered marine mammal, was reduced to 30 individuals as of February 2017. They are often killed by commercial fishing nets. As of March 2019, only 10 remain, according to The International Committee for the Recovery of the Vaquita.
HSUS, assert that trophy hunters, particularly from the United States, are playing a significant role in the decline of giraffes, which they refer to as a "silent extinction".
The surge in the mass killings by
poachers involved in the illegal ivory trade along with habitat loss is threatening African elephant populations. In 1979, their populations stood at 1.7 million; at present there are fewer than 400,000 remaining. Prior to European colonization, scientists believe Africa was home to roughly 20 million elephants. According to the Great Elephant Census, 30% of African elephants (or 144,000 individuals) disappeared over a seven-year period, 2007 to 2014. African elephants could become extinct by 2035 if poaching rates continue.
Fishing has had a devastating effect on marine organism populations for several centuries even before the explosion of destructive and highly effective fishing practices like
blue whales, North Atlantic right whales and over fifty species of sharks and rays are vulnerable to predation pressure from human fishing, in particular commercial fishing. A 2016 study published in Science concludes that humans tend to hunt larger species, and this could disrupt ocean ecosystems for millions of years. A 2020 study published in Science Advances found that around 18% of marine megafauna, including iconic species such as the Great white shark, are at risk of extinction from human pressures over the next century. In a worst-case scenario, 40% could go extinct over the same time period. According to a 2021 study published in Nature, 71% of oceanic shark and ray populations have been destroyed by overfishing (the primary driver of ocean defaunation) from 1970 to 2018, and are nearing the "point of no return" as 24 of the 31 species are now threatened with extinction, with several being classified as critically endangered.
If this pattern goes unchecked, the future oceans would lack many of the largest species in today’s oceans. Many large species play critical roles in ecosystems and so their extinctions could lead to ecological cascades that would influence the structure and function of future ecosystems beyond the simple fact of losing those species.
— Jonathan Payne, associate professor and chair of geological sciences at Stanford University
The golden toad of Costa Rica, extinct since around 1989. Its disappearance has been attributed to a confluence of several factors, including El Niño warming, fungus, habitat loss and the introduction of invasive species.
Millions of bats in the US have been dying off since 2012 due to a fungal infection known as white-nose syndrome that spread from European bats, who appear to be immune. Population drops have been as great as 90% within five years, and extinction of at least one bat species is predicted. There is currently no form of treatment, and such declines have been described as "unprecedented" in bat evolutionary history by Alan Hicks of the New York State Department of Environmental Conservation.
Megafauna were once found on every continent of the world, but are now almost exclusively found on the continent of Africa. In some regions, megafauna experienced population crashes and trophic cascades shortly after the earliest human settlers. Worldwide, 178 species of the world's largest mammals died out between 52,000 and 9,000 BC; it has been suggested that a higher proportion of African megafauna survived because they evolved alongside humans. The timing of South American megafaunal extinction appears to precede human arrival, although the possibility that human activity at the time impacted the global climate enough to cause such an extinction has been suggested.
List of extinct animals of Europe
Africa experienced the smallest decline in megafauna compared to the other continents. This is presumably due to the idea that Afroeurasian megafauna evolved alongside humans, and thus developed a healthy fear of them, unlike the comparatively tame animals of other continents. Unlike other continents, the megafauna of Eurasia went extinct over a relatively long period of time, possibly due to climate fluctuations fragmenting and decreasing populations, leaving them vulnerable to over-exploitation, as with the steppe bison (Bison priscus). The warming of the arctic region caused the rapid decline of grasslands, which had a negative effect on the grazing megafauna of Eurasia. Most of what once was mammoth steppe was converted to mire, rendering the environment incapable of supporting them, notably the woolly mammoth.
. It experienced a rapid decline in the late 1800s due to habitat destruction and intense hunting after the arrival of Europeans. The last wild bird is thought to have been shot in 1901.
There has been a debate as to the extent to which the disappearance of
humans in the Americas may extend back many thousands of years before the Clovis culture. The amount of correlation between human arrival and megafauna extinction is still being debated: for example, in Wrangel Island in Siberia the extinction of dwarf woolly mammoths (approximately 2000 BCE) did not coincide with the arrival of humans, nor did megafaunal mass extinction on the South American continent, although it has been suggested climate changes induced by anthropogenic effects elsewhere in the world may have contributed.
Comparisons are sometimes made between recent extinctions (approximately since the
industrial revolution) and the Pleistocene extinction near the end of the last glacial period. The latter is exemplified by the extinction of large herbivores such as the woolly mammoth and the carnivores that preyed on them. Humans of this era actively hunted the mammoth and the mastodon, but it is not known if this hunting was the cause of the subsequent massive ecological changes, widespread extinctions and climate changes.
The ecosystems encountered by the first Americans had not been exposed to human interaction, and may have been far less resilient to human made changes than the ecosystems encountered by industrial era humans. Therefore, the actions of the Clovis people, despite seeming insignificant by today's standards could indeed have had a profound effect on the ecosystems and wild life which was entirely unused to human influence.[attribution needed][neutrality is disputed]
Due to the older timeframe and the soil chemistry on the continent, very little
subfossil preservation evidence exists relative to elsewhere. However, continent-wide extinction of all genera weighing over 100 kilograms, and six of seven genera weighing between 45 and 100 kilograms occurred around 46,400 years ago (4,000 years after human arrival) and the fact that megafauna survived until a later date on the island of Tasmania following the establishment of a land bridge suggest direct hunting or anthropogenic ecosystem disruption such as fire-stick farming as likely causes. The first evidence of direct human predation leading to extinction in Australia was published in 2016.
A 2021 study found that the rate of extinction of Australia's megafauna is rather unusual, with some generalistic species having gone extinct earlier while highly specialised ones having become extinct later or even still surviving today. A mosaic cause of extinction with different anthropogenic and environmental pressures has been proposed.
The arrival of the first human settlers in the Azores saw the introduction of invasive plants and livestock to the archipelago, resulting in the extinction of at least two plant species on Pico Island. Lacustrine ecosystems were ravaged by human colonisation, as evidenced by hydrogen isotopes from C30 fatty acids recording hypoxic bottom waters caused by eutrophication in Lake Funda on Flores Island beginning between 1500 and 1600 AD.
In the Canary Islands, native thermophilous woodlands were decimated and two tree taxa were driven extinct following the arrival of its first humans, primarily as a result of increased fire clearance and soil erosion and the introduction of invasive pigs, goats, and rats. Invasive species introductions accelerated during the Age of Discovery when Europeans first settled the Macaronesian archipelago. The archipelago's laurel forests, though still negatively impacted, fared better due to being less suitable for human economic use.
Cabo Verde, like the Canary Islands, witnessed precipitous deforestation upon the arrival of European settlers and various invasive species brought by them in the archipelago, with the archipelago's thermophilous woodlands suffering the greatest destruction. Introduced species, overgrazing, increased fire incidence, and soil degradation have been attributed as the chief causes of Cabo Verde's ecological devastation.
Archaeological and paleontological digs on 70 different
Pacific islands suggested that numerous species became extinct as people moved across the Pacific, starting 30,000 years ago in the Bismarck Archipelago and Solomon Islands. It is currently estimated that among the bird species of the Pacific, some 2000 species have gone extinct since the arrival of humans, representing a 20% drop in the biodiversity of birds worldwide.
birds, insects, mollusks and fish; 30% of its organisms are endemic. Many of its species are endangered or have gone extinct, primarily due to accidentally introduced species and livestock grazing. Over 40% of its bird species have gone extinct, and it is the location of 75% of extinctions in the United States. Extinction has increased in Hawaii over the last 200 years and is relatively well documented, with extinctions among native snails used as estimates for global extinction rates.
Radiocarbon dating of multiple subfossil specimens shows that now extinct giant lemurs
were present in Madagascar until after human arrival.
Within 500 years of the arrival of humans between 2,500 and 2,000 years ago, nearly all of Madagascar's distinct, endemic and geographically isolated megafauna became extinct. The largest animals, of more than 150 kilograms (330 lb), were extinct very shortly after the first human arrival, with large and medium-sized species dying out after prolonged hunting pressure from an expanding human population moving into more remote regions of the island around 1000 years ago. The eight or more species of elephant birds, giant flightless ratites in the genera Aepyornis, Vorombe, and Mullerornis, are extinct from over-hunting, as well as 17 species of lemur, known as giant, subfossil lemurs. Some of these lemurs typically weighed over 150 kilograms (330 lb), and their fossils have provided evidence of human butchery on many species. Smaller fauna experienced initial increases due to decreased competition, and then subsequent declines over the last 500 years. All fauna weighing over 10 kilograms (22 lb) died out. The primary reasons for the decline of Madagascar's biota, which at the time was already stressed by natural aridification, were human hunting, herding, farming, and forest clearing, all of which persist and threaten Madagascar's remaining taxa today. The natural ecosystems of Madagascar as a whole were further impacted by the much greater incidence of fire as a result of anthropogenic fire production; evidence from Lake Amparihibe on the island of Nosy Be indicates a shift in local vegetation from intact rainforest to a fire-disturbed patchwork of grassland and woodland between 1300 and 1000 BP.
List of New Zealand animals extinct in the Holocene
plant-based diets, and increasing the number and size of terrestrial and marine protected areas are the keys to avoiding or limiting biodiversity loss and a possible sixth mass extinction. Rodolfo Dirzo and Paul R. Ehrlich suggest that "the one fundamental, necessary, 'simple' cure, ... is reducing the scale of the human enterprise."
A 2018 article in Science advocated for the global community to designate 30 percent of the planet by 2030, and 50 percent by 2050, as protected areas in order to mitigate the contemporary extinction crisis. It highlighted that the human population is projected to grow to 10 billion by the middle of the century, and consumption of food and water resources is projected to double by this time.
"From COVID-19 to massive wildfires, floods, melting glaciers and unprecedented heat, our failure to meet the Aichi (biodiversity) targets — protect our our home — has very real consequences. We can no longer afford to cast nature to the side."
Some scientists have proposed keeping extinctions below 20 per year for the next century as a global target to reduce species loss, which is the biodiversity equivalent of the 2 °C climate target, although it is still much higher than the normal background rate of two per year prior to anthropogenic impacts on the natural world.
An October 2020 report on the "era of pandemics" from
pandemics. The report offers several policy options to reduce such risk, such as taxing meat production and consumption, cracking down on the illegal wildlife trade, removing high disease-risk species from the legal wildlife trade, and eliminating subsidies to businesses which are harmful to the environment. According to marine zoologist John Spicer, "the COVID-19 crisis is not just another crisis alongside the biodiversity crisis and the climate change crisis. Make no mistake, this is one big crisis – the greatest that humans have ever faced."
According to a 2021 paper published in
Frontiers in Conservation Science, humanity almost certainly faces a "ghastly future" of mass extinction, biodiversity collapse, climate change and their impacts unless major efforts to change human industry and activity are rapidly undertaken.
A 2022 report published in Science warned that 44% of earth's terrestrial surface, or 24.7 million square miles, must to be conserved and made "ecologically sound" in order to prevent further biodiversity loss.
^Phylogenetic diversity (PD) is the sum of the phylogenetic branch lengths in years connecting a set of species to each other across their phylogenetic tree, and measures their collective contribution to the tree of life.
^This may refer to groups of animals endangered by climate change. For example, during a catastrophic drought, remaining animals would be gathered around the few remaining watering holes, and thus become extremely vulnerable.
^Hollingsworth, Julia (June 11, 2019). "Almost 600 plant species have become extinct in the last 250 years". CNN. Retrieved January 14, 2020. The research -- published Monday in Nature, Ecology & Evolution journal -- found that 571 plant species have disappeared from the wild worldwide, and that plant extinction is occurring up to 500 times faster than the rate it would without human intervention.
^"Without humans, the whole world could look like Serengeti". EurekAlert!. Retrieved August 16, 2020. The existence of Africa's many species of mammals is thus not due to an optimal climate and environment, but rather because it is the only place where they have not yet been eradicated by humans. The underlying reason includes evolutionary adaptation of large mammals to humans as well as greater pest pressure on human populations in long-inhabited Africa in the past.
. Much less frequently mentioned are, however, the ultimate drivers of those immediate causes of biotic destruction, namely, human overpopulation and continued population growth, and overconsumption, especially by the rich. These drivers, all of which trace to the fiction that perpetual growth can occur on a finite planet, are themselves increasing rapidly
^ abcdefStokstad, Erik (5 May 2019). "Landmark analysis documents the alarming global decline of nature". Science. AAAS. Retrieved 26 August 2020. For the first time at a global scale, the report has ranked the causes of damage. Topping the list, changes in land use—principally agriculture—that have destroyed habitat. Second, hunting and other kinds of exploitation. These are followed by climate change, pollution, and invasive species, which are being spread by trade and other activities. Climate change will likely overtake the other threats in the next decades, the authors note. Driving these threats are the growing human population, which has doubled since 1970 to 7.6 billion, and consumption. (Per capita of use of materials is up 15% over the past 5 decades.)
(PDF) on 15 December 2019. Retrieved 12 July 2018. Moreover, we have unleashed a mass extinction event, the sixth in roughly 540 million years, wherein many current life forms could be annihilated or at least committed to extinction by the end of this century.
^ abMcGrath, Matt (6 May 2019). "Humans 'threaten 1m species with extinction'". BBC. Retrieved 3 August 2021. Pushing all this forward, though, are increased demands for food from a growing global population and specifically our growing appetite for meat and fish.
. In the past 500 years, humans have triggered a wave of extinction, threat, and local population declines that may be comparable in both rate and magnitude with the five previous mass extinctions of Earth’s history
^Woodward, Aylin (April 8, 2019). "So many animals are going extinct that it could take Earth 10 million years to recover". Business Insider. Retrieved April 9, 2019. Lowery doesn't think we've strayed into Sixth Extinction territory yet. But he and Fraass agree that squabbling over what constitutes that distinction is beside the point. "We have to work to save biodiversity before it's gone. That's the important takeaway here," Lowery said. There is consensus on one aspect of the extinction trend, however: Homo sapiens are to blame. According to a 2014 study, current extinction rates are 1,000 times higher than they would be if humans weren't around.
^Brannen, Peter (13 June 2017). "Earth Is Not in the Midst of a Sixth Mass Extinction". The Atlantic. Retrieved 28 November 2020. Many of those making facile comparisons between the current situation and past mass extinctions don’t have a clue about the difference in the nature of the data, much less how truly awful the mass extinctions recorded in the marine fossil record actually were.
. It was only with the rise of capitalism over the past few hundred years, and the breathtaking acceleration of industrialization from the 1950s, that on a planetary scale things began to tip out of balance.
. The advent of the Anthropocene coincided with a planetary rift, as the human economy under capitalism heedlessly crossed, or began to cross, Earth System boundaries, fouling its own nest and threatening the destruction of the planet as a safe home for humanity.
^Briggs, Helen (May 26, 2020). "'Billions of years of evolutionary history' under threat". BBC. Retrieved October 5, 2020. The researchers calculated the amount of evolutionary history - branches on the tree of life - that are currently threatened with extinction, using extinction risk data for more than 25,000 species. They found a combined 50 billion years of evolutionary heritage, at least, were under threat from human impacts such as urban development, deforestation and road building.
^Ketcham, Christopher (December 3, 2022). "Addressing Climate Change Will Not "Save the Planet"". The Intercept. Retrieved December 6, 2022. When it comes to effects on wildlife, climate change is more like a mule, slow and plodding. Yes, a warmed atmosphere is projected to be a significant factor in the extinction crisis in future decades, but what’s destroying species today is habitat fragmentation and loss, overhunting and overexploitation, agricultural expansion, pollution, and industrial development. It isn’t climate change that caused a 69 percent loss in total wildlife populations between 1970 and 2018, according to a World Wildlife Fund study published this year. The cause is too many people demanding too much from ecosystems, or human overshoot of the biophysical carrying capacity of the Earth.
deBuys, William (March 2015). "The Politics of Extinction – A Global War on Nature". Tom Dispatch. Uncounted species – not just tigers, gibbons, rhinos, and saola, but vast numbers of smaller mammals, amphibians, birds, and reptiles – are being pressed to the brink. We’ve hardly met them and yet, within the vastness of the universe, they and the rest of Earth’s biota are our only known companions. Without them, our loneliness would stretch to infinity.