Various start dates for the Anthropocene have been proposed, ranging from the beginning of the Agricultural Revolution 12,000–15,000 years ago, to as recent as the 1960s. The ratification process is ongoing, and thus a date remains to be decided definitively, but the peak in radionuclides fallout consequential to atomic bomb testing during the 1950s has been more favoured than others, locating a possible beginning of the Anthropocene to the detonation of the first atomic bomb in 1945, or the Partial Nuclear Test Ban Treaty in 1963.
In 2008, the Stratigraphy Commission of the Geological Society of London considered a proposal to make the Anthropocene a formal unit of geological epoch divisions. A majority of the commission decided the proposal had merit and should be examined further. Independent working groups of scientists from various geological societies have begun to determine whether the Anthropocene will be formally accepted into the Geological Time Scale.
The term "anthropocene" is informally used in scientific contexts. The Geological Society of America entitled its 2011 annual meeting: Archean to Anthropocene: The past is the key to the future. The new epoch has no agreed start-date, but one proposal, based on atmospheric evidence, is to fix the start with the Industrial Revolution c. 1780, with the invention of the steam engine. Other scientists link the new term to earlier events, such as the rise of agriculture and the Neolithic Revolution (around 12,000 years BP). Evidence of relative human impact – such as the growing human influence on land use, ecosystems, biodiversity, and species extinction – is substantial; scientists think that human impact has significantly changed (or halted) the growth of biodiversity. Those arguing for earlier dates posit that the proposed Anthropocene may have begun as early as 14,000–15,000 years BP, based on geologic evidence; this has led other scientists to suggest that "the onset of the Anthropocene should be extended back many thousand years";:1 this would be essentially synonymous with the current term, Holocene.
The Trinity test in July 1945 has been proposed as the start of the Anthropocene.
In January 2015, 26 of the 38 members of the International Anthropocene Working Group published a paper suggesting the Trinity test on 16 July 1945 as the starting point of the proposed new epoch. However, a significant minority supports one of several alternative dates. A March 2015 report suggested either 1610 or 1964 as the beginning of the Anthropocene. Other scholars point to the diachronous character of the physical strata of the Anthropocene, arguing that onset and impact are spread out over time, not reducible to a single instant or date of start.
A January 2016 report on the climatic, biological, and geochemical signatures of human activity in sediments and ice cores suggested the era since the mid-20th century should be recognised as a geological epoch distinct from the Holocene.
The Anthropocene Working Group met in Oslo in April 2016 to consolidate evidence supporting the argument for the Anthropocene as a true geologic epoch. Evidence was evaluated and the group voted to recommend "Anthropocene" as the new geological age in August 2016. Should the International Commission on Stratigraphy approve the recommendation, the proposal to adopt the term will have to be ratified by the IUGS before its formal adoption as part of the geologic time scale.
As early as 1873, the Italian geologist Antonio Stoppani acknowledged the increasing power and effect of humanity on the Earth's systems and referred to an 'anthropozoic era'.
Although the biologist Eugene F. Stoermer is often credited with coining the term "anthropocene", it was in informal use in the mid-1970s. Paul J. Crutzen is credited with independently re-inventing and popularising it. Stoermer wrote, "I began using the term 'anthropocene' in the 1980s, but never formalised it until Paul contacted me." Crutzen has explained, "I was at a conference where someone said something about the Holocene. I suddenly thought this was wrong. The world has changed too much. So I said: 'No, we are in the Anthropocene.' I just made up the word on the spur of the moment. Everyone was shocked. But it seems to have stuck.":21 In 2008, Zalasiewicz suggested in GSA Today that an anthropocene epoch is now appropriate.
Homogenocene (from old Greek: homo-, same; geno-, kind; kainos-, new; and -cene, period) is a more specific term used to define our current geologicalepoch, in which biodiversity is diminishing and biogeography and ecosystems around the globe seem more and more similar to one another mainly due to invasive species that have been introduced around the globe either on purpose (crops, livestock) or inadvertently.
The term Homogenocene was first used by Michael Samways in his editorial article in the Journal of Insect Conservation from 1999 titled "Translocating fauna to foreign lands: Here comes the Homogenocene."
The term was used again by John L. Curnutt in the year 2000 in Ecology, in a short list titled "A Guide to the Homogenocene", which reviewed Alien species in North America and Hawaii: impacts on natural ecosystems by George Cox. Charles C. Mann, in his acclaimed book 1493: Uncovering the New World Columbus Created, gives a bird's eye view of the mechanisms and ongoing implications of the homogenocene.[full citation needed]
The human impact on biodiversity forms one of the primary attributes of the Anthropocene. Humankind has entered what is sometimes called the Earth's sixth major extinction. Most experts agree that human activities have accelerated the rate of species extinction. The exact rate remains controversial – perhaps 100 to 1000 times the normal background rate of extinction. A 2010 study found that
marine phytoplankton – the vast range of tiny algae species accounting for roughly half of Earth's total photosynthetic biomass – has declined substantially in the world's oceans over the past century. From 1950 alone, algal biomass decreased by around 40%, probably in response to ocean warming
– and that the decline had gathered pace in recent years. Some authors have postulated that without human impacts the biodiversity of the planet would continue to grow at an exponential rate.
Increases in global rates of extinction have been elevated above background rates since at least 1500, and appear to have accelerated in the 19th century and further since. A New York Times op-ed on 13 July 2012 by ecologist Roger Bradbury predicted the end of biodiversity for the oceans, labelling coral reefs doomed: "Coral reefs will be the first, but certainly not the last, major ecosystem to succumb to the Anthropocene." This op-ed quickly generated much discussion among conservationists; The Nature Conservancy rebutted Bradbury on its website, defending its position of protecting coral reefs despite continued human impacts causing reef declines.
In a pair of studies published in 2015, extrapolation from observed extinction of Hawaiian snails of the family Amastridae, led to the conclusion that "the biodiversity crisis is real", and that 7% of all species on Earth may have disappeared already. Human predation was noted as being unique in the history of life on Earth as being a globally distributed 'superpredator', with predation of the adults of other apex predators and with widespread impact on food webs worldwide. A study published in May 2017 in Proceedings of the National Academy of Sciences noted that a "biological annihilation" akin to a sixth mass extinction event is underway as a result of anthropogenic causes. The study suggested that as much as 50% of animal individuals that once lived on Earth are already extinct. A different study published in PNAS in May 2018 says that since the dawn of human civilization, 83% of wild mammals have disappeared. Today, livestock makes up 60% of the biomass of all mammals on earth, followed by humans (36%) and wild mammals (4%). According to the 2019 Global Assessment Report on Biodiversity and Ecosystem Services by IPBES, 25% of plant and animal species are threatened with extinction.
Permanent changes in the distribution of organisms from human influence will become identifiable in the geologic record. Researchers have documented the movement of many species into regions formerly too cold for them, often at rates faster than initially expected. This has occurred in part as a result of changing climate, but also in response to farming and fishing, and to the accidental introduction of non-native species to new areas through global travel. The ecosystem of the entire Black Sea may have changed during the last 2000 years as a result of nutrient and silica input from eroding deforested lands along the Danube River.
Researchers have found that the growth of the human population and expansion of human activity has resulted in many species of animals that are normally active during the day, such as elephants, tigers and boars, becoming nocturnal to avoid contact with humans.
One geological symptom resulting from human activity is increasing atmosphericcarbon dioxide (CO 2) content. During the glacial–interglacial cycles of the past million years, natural processes have varied CO 2 by approximately 100 ppm (from 180 ppm to 280 ppm) As of 2013[update], anthropogenic net emissions of CO 2 have increased atmospheric concentration by a comparable amount: From 280 ppm (Holocene or pre-industrial "equilibrium") to approximately 400 ppm, with 2015–2016 monthly monitoring data of CO 2 displaying a rising trend above 400 ppm. This signal in the Earth's climate system is especially significant because it is occurring much faster, and to a greater extent, than previous, similar changes. Most of this increase is due to the combustion of fossil fuels such as coal, oil, and gas, although smaller fractions result from cement production and from land-use changes (such as deforestation).
Changes in drainage patterns traceable to human activity will persist over geologic time in large parts of the continents where the geologic regime is erosional. This includes the paths of roads and highways defined by their grading and drainage control. Direct changes to the form of the Earth's surface by human activities (e.g., quarrying, landscaping) also record human impacts.
It has been suggested the deposition of calthemite formations are one example of a natural process which has not previously occurred prior to the human modification of the Earth's surface, and therefore represents a unique process of the Anthropocene. Calthemite is a secondary deposit, derived from concrete, lime, mortar or other calcareous material outside the cave environment.Calthemites grow on or under, man-made structures (including mines and tunnels) and mimic the shapes and forms of cave speleothems, such as stalactites, stalagmites, flowstone etc.
Human activities like deforestation and road construction are believed to have elevated average total sediment fluxes across the Earth's surface. However, construction of dams on many rivers around the world means the rates of sediment deposition in any given place do not always appear to increase in the Anthropocene. For instance, many river deltas around the world are actually currently starved of sediment by such dams, and are subsiding and failing to keep up with sea level rise, rather than growing.
Increases in erosion due to farming and other operations will be reflected by changes in sediment composition and increases in deposition rates elsewhere. In land areas with a depositional regime, engineered structures will tend to be buried and preserved, along with litter and debris. Litter and debris thrown from boats or carried by rivers and creeks will accumulate in the marine environment, particularly in coastal areas. Such man-made artifacts preserved in stratigraphy are known as "technofossils".
Changes in biodiversity will also be reflected in the fossil record, as will species introductions. An example cited is the domestic chicken, originally the red junglefowlGallus gallus, native to south-east Asia but has since become the world's most common bird through human breeding and consumption, with over 60 billion consumed annually and whose bones would become fossilised in landfill sites. Hence, landfills are important resources to find "technofossils".
In terms of trace elements, there are distinct signatures left by modern societies. For example, in the Upper Fremont Glacier in Wyoming, there is a layer of chlorine present in ice cores from 1960's atomic weapon testing programs, as well as a layer of mercury associated with coal plants in the 1980s.[full citation needed] From 1945 to 1951, nuclear fallout is found locally around atomic device test sites, whereas from 1952 to 1980, tests of thermonuclear devices have left a clear, global signal of excess 14 C , 239 Pu , and other artificial radionuclides.[full citation needed] The highest global concentration of radionuclides was in 1965, one of the dates which has been proposed as a possible benchmark for the start of the formally defined Anthropocene.
Human burning of fossil fuels has also left distinctly elevated concentrations of black carbon, inorganic ash, and spherical carbonaceous particles in recent sediments across the world. Concentrations of these components increases markedly and almost simultaneously around the world beginning around 1950.
While much of the environmental change occurring on Earth is suspected to be a direct consequence of the Industrial Revolution, William Ruddiman has argued that the proposed Anthropocene began approximately 8,000 years ago with the development of farming and sedentary cultures. At this point, humans were dispersed across all of the continents (except Antarctica), and the Neolithic Revolution was ongoing. During this period, humans developed agriculture and animal husbandry to supplement or replace hunter-gatherer subsistence. Such innovations were followed by a wave of extinctions, beginning with large mammals and land birds. This wave was driven by both the direct activity of humans (e.g. hunting) and the indirect consequences of land-use change for agriculture. Landscape-scale burning by prehistoric hunter-gathers may have been an additional early source of anthropogenic atmospheric carbon.
From the past to present, some authors consider the Anthropocene and the Holocene to be the same or coeval geologic time span, and others viewed the Anthropocene as being a bit more recent. Ruddiman claims that the Anthropocene, has had significant human impact on greenhouse gas emissions, which began not in the industrial era, but rather 8,000 years ago, as ancient farmers cleared forests to grow crops. Ruddiman's work has, in turn, been challenged with data from an earlier interglaciation ("Stage 11", approximately 400,000 years ago) which suggests that 16,000 more years must elapse before the current Holocene interglaciation comes to an end, and that thus the early anthropogenic hypothesis is invalid. Furthermore, the argument that "something" is needed to explain the differences in the Holocene is challenged by more recent research showing that all interglacials differ.
Although 8,000 years ago the planet sustained a few million people, it was still fundamentally pristine.[dubious – discuss] This claim is the basis for an assertion that an early date for the proposed Anthropocene term does account for a substantial human footprint on Earth.
One plausible starting point of the Anthropocene could be at c. 2,000 years ago, which roughly coincides with the start of the final phase of Holocene, the Sub Atlantic.
At this time, the Roman Empire encompassed large portions of Europe, the Middle East, and North Africa. In China the classical dynasties were flowering. The Middle kingdoms of India had already the largest economy of the ancient and medieval world. The Napata/Meroitic kingdom extended over the current Sudan and Ethiopia. The Olmecs controlled central Mexico and Guatemala, and the pre-Incan Chavín people managed areas of northern Peru. Although often apart from each other and intermixed with buffering ecosystems, the areas directly impacted by these civilisations and others were large. Additionally, some activities, such as mining, implied much more widespread perturbation of natural conditions. Over the last 11,500 years or so humans have spread around Earth, increased in number, and profoundly altered the material world. They have taken advantage of global environmental conditions not of their own making. The end of the last glacial period – when as much as 30% of Earth's surface was ice-bound – led to a warmer world with more water (H 2O). Although humans existed in the previous Pleistocene epoch, it is only in the recent Holocene period that they have flourished. Today there are more humans alive than at any previous point in Earth's history.
European colonisation of the Americas
Maslin and Lewis argue that the start of the Anthropocene should be dated to the Orbis Spike, a trough in carbon dioxide levels associated with the arrival of Europeans in the Americas. Reaching a minimum around 1610, global carbon dioxide levels were depressed below 285 parts per million, largely as a result of sequestration due to forest regrowth in the Americas. This was likely caused by indigenous peoples abandoning farmland following a sharp population decline due to initial contact with European diseases- around 50 million people or 90% of the indigenous population may have succumbed. For Maslin and Lewis, the Orbis Spike represents a GSSP, a kind of marker used to define the start of a new geological period. They also go on to say that associating the Anthropocene to European arrival in the Americas makes sense given that the continent's colonisation was instrumental in the development of global trade networks and the capitalist economy, which played a significant role in initiating the Industrial Revolution and the Great Acceleration.
A number of other anthropologists, geographers, and postcolonial theorists have linked the Anthropocene to the rise of European colonialism.
Crutzen proposed the Industrial Revolution as the start of Anthropocene. Lovelock proposes that the Anthropocene began with the first application of the Newcomen atmospheric engine in 1712. The Intergovernmental Panel on Climate Change takes the pre-industrial era (chosen as the year 1750) as the baseline related to changes in long-lived, well mixed greenhouse gases. Although it is apparent that the Industrial Revolution ushered in an unprecedented global human impact on the planet, much of Earth's landscape already had been profoundly modified by human activities. The human impact on Earth has grown progressively, with few substantial slowdowns.
In May 2019 the twenty-nine members of the Anthropocene Working Group (AWG) proposed a start date for the Epoch in the mid-twentieth century, as that period saw "a rapidly rising human population accelerated the pace of industrial production, the use of agricultural chemicals and other human activities. At the same time, the first atomic-bomb blasts littered the globe with radioactive debris that became embedded in sediments and glacial ice, becoming part of the geologic record." The official start-dates, according to the panel, would coincide with either the radionuclides released into the atmosphere from bomb detonations in 1945, or coinciding with the Limited Nuclear Test Ban Treaty of 1963.
A marker that accounts for a substantial global impact of humans on the total environment, comparable in scale to those associated with significant perturbations of the geological past, is needed in place of minor changes in atmosphere composition.
A useful candidate for this purpose is the pedosphere, which can retain information of its climatic and geochemical history with features lasting for centuries or millennia. Human activity is now firmly established as the sixth factor of soil formation. It affects pedogenesis either directly, by, for example, land levelling, trenching and embankment building for various purposes, organic matter enrichment from additions of manure or other waste, organic matter impoverishment due to continued cultivation, compaction from overgrazing or, indirectly, by drift of eroded materials or pollutants. Anthropogenic soils are those markedly affected by human activities, such as repeated ploughing, the addition of fertilisers, contamination, sealing, or enrichment with artefacts (in the World Reference Base for Soil Resources they are classified as Anthrosols and Technosols). They are recalcitrant repositories of artefacts and properties that testify to the dominance of the human impact, and hence appear to be reliable markers for the Anthropocene. Some anthropogenic soils may be viewed as the 'golden spikes' of geologists (Global Boundary Stratotype Section and Point), which are locations where there are strata successions with clear evidences of a worldwide event, including the appearance of distinctive fossils. Drilling for fossil fuels has also created holes and tubes which are expected to be detectable for millions of years. The astrobiologist David Grinspoon has proposed that the site of the Apollo 11 Lunar landing, with the disturbances and artifacts that are so uniquely characteristic of our species' technological activity and which will survive over geological time spans could be considered as the 'golden spike' of the Anthropocene.
The concept of the Anthropocene has also been approached via humanities such as philosophy, literature and art. In the scholarly world, it has been the subject of increasing attention through special journal issues, conferences, and disciplinary reports. The Anthropocene, its attendant timescale, and ecological implications prompt questions about death and the end of civilisation, memory and archives, the scope and methods of humanistic inquiry, and emotional responses to the "end of nature". It has been also criticised as an ideological construct.
Some environmental scholars suggest that "Capitalocene" is a more historically appropriate term. At the same time, others suggest that the Anthropocene ignores systematic inequalities, such as imperialism and racism, that have contributed to the environmental degradation that would mark the Epoch. In this vein, some thinkers have proposed the "Plantationocene" as a more appropriate term to call attention to the role that plantation agriculture has played in the formation of the Epoch, as it marks "the ways that plantation logics organize modern economies, environments, bodies, and social relations".
Historians have actively engaged the Anthropocene. In 2000, the same year that Paul Crutzen coined the term, world historian John McNeill published Something New Under the Sun tracing the rise of human societies' unprecedented impact on the planet in the twentieth century. In 2001, historian of science Naomi Oreskes revealed the systematic efforts to undermine trust in climate change science and went on to detail the corporate interests delaying action on the environmental challenge. Both McNeill and Oreskes became members of the Anthropocene Working Group because of their work correlating human activities and planetary transformation. In 2009, Dipesh Chakrabarty pointed to the dilemma that the Anthropocene poses for the practice of history: on the one hand, it spells "the collapse of the age-old humanist distinction between natural history and human history" yet, on the other, societies and individuals do not experience themselves as "species." In 2014, Julia Adeney Thomas highlighted problems of scale and value as the reasons for this irresolvable tension between human stories and scientific ones. Since 2007, historians and scientists have been actively collaborating on multidisciplinary approaches to the Anthropocene.. In 2016, historians Christophe Bonneuil and Jean Baptiste-Fressoz published The Shock of the Anthropocene: The Earth, History and Us in an attempt to provide "the first critical history of the Anthropocene" through engagement with the history of science, world history, and human development 
The concept gained attention of the public via documentary films such as The Antarctica Challenge: A Global Warning, The Polar Explorer, L'homme a mangé la Terre, Anthropocene: The Human Epoch and Anthropocene.
David Grinspoon makes a further distinction in the Anthropocene, namely the "proto-Anthropocene" and "mature Anthropocene". He also mentions the term "Terra Sapiens", or Wise Earth.
In 2019, the English musician Nick Mulvey released a music video on YouTube named "In The Anthropocene". In cooperation with Sharp's Brewery, the song was recorded on 105 vinyl records made of washed-up plastic from the Cornish coast.
"The Anthropocene Reviewed" is a podcast by author John Green, where he "reviews different facets of the human-centered planet on a five-star scale".
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