To hear his colleagues speak of Earth’s current state without reference to these profound anthropogenic changes was just too much to bear. It was time to accept that the relatively stable conditions of the Holocene Epoch were over.

In this first publication, Crutzen and Stoermer linked the Anthropocene with carbon dioxide emissions from fossil fuel combustion and dated it to the start of the Industrial Revolution at the end of the 18th century.

humans are changing Earth in unprecedented ways. Global climate change, acidifying oceans, shifting global cycles of carbon, nitrogen, and other elements, forests and other natural habitats transformed into farms and cities, widespread pollution, radioactive fallout, plastic accumulation, the course of rivers altered, mass extinction of species, human transport and introduction of species around the world. These are just some of the many different human-induced global environmental changes that will most likely leave a lasting record in rock: the basis for marking new intervals of geologic time.

Proposals for the start of the Anthropocene range from early human control of fire, to the rise of agriculture more than 10,000 years ago, to the peak year of nuclear fallout in 1964, supported by evidence ranging from gas bubbles trapped in ice cores and widespread deposits of soot and radionuclides, to the appearance of domesticated maize pollen in sediment cores around the world. And this is just to scrape the surface of the many disputes instigated by the Anthropocene proposal.

The significance of the Anthropocene resides in its role as a new lens through which age-old narratives and philosophical questions are being revisited and rewritten. The Anthropocene is both a new narrative relating humans and nature and a bold new scientific paradigm—a ‘Second Copernican Revolution’—with the potential to radically revise the way we think of what it means to be human.

Earth, one of eight planets in an irregular orbit around a typical yellow dwarf star, was located in the spiral arm of a galaxy of more than 100 billion stars, in one of more than 100 billion galaxies, together holding about 1 billion trillion stars in a continuously expanding universe.

the ‘great forces of nature’ were no godlike powers, but rather, the processes underpinning Earth’s functioning as a complex dynamic system.

Vladimir Vernadsky developed the first modern scientific model of Earth as a complex system based on dynamic interactions among the ‘spheres’, in his 1926 book, The Biosphere (Figure

By the early 1970s, James Lovelock and Lynn Margulis had an answer. Living organisms, acting collectively as the biosphere, were themselves responsible for regulating Earth’s climate and sustaining the conditions necessary to support life. Life gave birth to life itself. Gaia was reborn in the landmark hypothesis that sparked the rise of Earth system science.

The Gaia hypothesis holds that the biosphere regulates Earth’s climate by acting like a thermostat. When Earth heats up, the biosphere responds by producing cooling effects. For example, organisms increase their uptake of greenhouse gases from the atmosphere and release fine particles—aerosols—into the air, helping to form clouds that reflect the sun’s energy. In response to a cooling Earth, the biosphere produced opposite effects, counteracting cooling by producing warming effects—increasing greenhouse gases and reducing aerosols in the atmosphere. In this way, the biosphere could stabilize Earth’s temperature through a ‘negative feedback’ system, countering the warming effects of increased solar energy—a process external to Earth. Negative feedbacks might also balance out the heating and cooling effects caused by processes internal to the Earth system, such as the release of greenhouse gases and aerosols by volcanoes.

To understand Earth’s remarkable long-term stability and ability to sustain life, this must be understood as the product of a complex system of interacting positive and negative feedbacks which shape the flows of matter and energy among the spheres.

Photosynthesis changed everything. Over hundreds of millions of years, photosynthetic organisms, mostly bacteria, would fill Earth’s atmosphere with O2.

Earth system science continues to investigate the causes of dynamic changes in Earth’s functioning. Perhaps the best studied of these is the claim that humans are now ‘overwhelming the great forces of nature’—a claim now supported by conclusive evidence that humans are causing unprecedented changes in Earth’s functioning as a system. Moreover, these anthropogenic changes have the potential to produce even more rapid, surprising, and potentially catastrophic consequences as a result of tipping points and other complex feedbacks within the Earth system.

To declare a new interval of geologic time, geologists would need to apply their own scientific methods, procedures, and evidence. It would be necessary to show that humans have left a clear, globally identifiable marker in the rocks.

from a pragmatic, stratigraphic, point of view, only one proposal presented a relatively straightforward, unambiguous, basis for a global, isochronous, stratigraphic marker: the spread of radioactive fallout from nuclear weapons testing, beginning with the Trinity Test of 1945.

striking inflection point around 1950 in virtually all of the human activities and Earth system changes they examined, after which rates of change become far steeper and in some cases almost exponential (Figures 14 and 15).

the need to understand anthropogenic global environmental change as a complex, multi-causal, system-level set of processes affecting the entire Earth system. Humans were doing a lot more than just changing Earth’s atmosphere and climate, they were also causing global changes in biodiversity, polluting the oceans with fertilizer runoff from agriculture, altering the flows of rivers to the sea, and transforming natural habitats around the world. Human influences in the global environment could not be reduced simply to fossil fuel combustion or the production of industrial chemicals. Population growth, the ‘domestication’ of land for agriculture, economic development, and even foreign direct investment were all part of the mix of human driving forces that were altering Earth’s functioning as a system. Anthropogenic global environmental change was a multidimensional process.

three-quarters of the terrestrial biosphere has been transformed directly and indirectly by human use of land. Less than one-quarter remains free of direct human impacts, and mostly in the less productive, colder, and drier regions of the terrestrial biosphere, though some also remain in the Tropics, where endemic diseases and other obstacles limit human settlement.

there is perhaps no greater single environmental transformation than the cultivation of crops, beginning with the clearing of land and tillage. Vegetation is removed, usually by burning, emitting carbon dioxide. Soils are uncovered, leading to erosion and loss. Disturbance, tillage, and the draining of wetlands cause abundant soil organic matter to decompose, releasing yet more carbon dioxide. Flooding soils to produce rice releases large amounts of methane gas (CH4), each molecule having more than ten times the greenhouse warming potential of carbon dioxide (though it spends less time in the atmosphere than CO2). Use of nitrogen-rich fertilizers (both manures and synthetic fertilizers) releases nitrous oxide (N2O), an even more potent greenhouse gas with more than 100 times the warming potential per molecule of carbon dioxide, and very stable.

Domesticated chickens are now Earth’s most abundant bird and cattle biomass alone exceeds that of all other living vertebrate animals combined—including humans.

since the 1950s, the terrestrial hydrosphere—Earth’s freshwater systems—has been transformed profoundly by human activities and limits to freshwater availability have become a matter of serious global concern.

Outside of a few freshwater and coastal habitats, traditional hunting and foraging pressures were generally insufficient to cause major population declines and extinctions and the open ocean remained only lightly influenced. All of that changed with industrial scale fishing, as fleets of ‘factory ships’ expanded across the oceans.

Nitrogen, in the form of highly stable and unreactive N2 gas, is the most abundant element in Earth’s atmosphere (78 per cent by volume). Yet, perhaps surprisingly, it is also the most common limiting nutrient for plant growth on land and in the sea. This is because plants (and most bacteria) can only take up and utilize reactive, ‘available’, forms of nitrogen: as ammonium (NH4 +) and nitrate (NO3 −) ions. The process of converting stable N2 into available nitrogen requires huge amounts of energy. Only a few bacterial species have evolved the specialized high-energy metabolism needed to ‘fix’ nitrogen, by cracking N2 to produce ammonium, though many bacteria can easily convert ammonium to nitrate.

the Haber–Bosch process transformed Earth’s nitrogen cycle. By combining large amounts of energy and carbon (usually methane) with N2 gas, their process fixed nitrogen into ammonium that could be used for fertilizer and other industrial processes, including bombs. Synthetic nitrogen fertilizers dramatically increased crop yields, often doubling them or more, especially when modern crop varieties were bred to take advantage of them—the basis for the ‘Green Revolution’ in agriculture that spread across the world beginning in the 1950s. With far higher yields, crop production increased without the need for an equivalent increase in land given over to cultivation; most of the 20th century’s expansion of agricultural land use has supported livestock production. At the same time, nitrogen fertilizers, especially when over-applied, have polluted ground and surface waters with nitrates, causing health risks, and saturated coastal ecosystems with nitrogen, producing algal blooms and dead zones. Emissions of nitrous oxide from fertilized fields are now an increasingly significant source of greenhouse gases in Earth’s atmosphere. In addition to artificial nitrogen fixation, the combustion of coal, petroleum, and biomass also releases acidic forms of nitrogen gases, the nitric oxides (NO and NO2), that together with sulphur oxides produce ‘acid rain’, which caused widespread environmental damage in the 1980s and 1990s before these acidic emissions from coal-fired power plants and unregulated vehicle engines were regulated and brought under control.

Anthropogenic transformation of the global biogeochemical cycle of nitrogen is one of the most striking examples of human alteration of Earth’s functioning as a system (Figure 17). Before the 20th century, the industrial process behind this profound Earth system transformation did not even exist. From the 1950s on, artificial nitrogen fixation accelerated, helping human transformation of Earth to reach unprecedented levels.

is likely that Earth is now hotter, on average, than at any other time in more than 100,000 years.

John McNeill. His prescient 2000 book Something New Under the Sun documented an unprecedented shift in the scale and intensity of social and environmental change in the 20th century together with its acceleration after 1950. Steffen, Crutzen, and McNeill later combined forces, further establishing the Great Acceleration as the leading narrative explaining the rise of humans as a ‘great force of nature’ and an Earth system transition to the Anthropocene after 1950.

Archaeologists are the stratigraphers of the human world, specializing in reading the material records left by human societies over the long term, often from their very first beginnings. And like the stratigraphers of geology, archaeologists serve as the timekeepers of humanity, dedicated to reconstructing the social and environmental history of human societies from the physical records left behind. Over decades, their research has amassed an impressive body of evidence demonstrating that humans have dramatically altered terrestrial environments around the world starting in the late Pleistocene.

an evolutionary process termed ‘niche construction’ by which organisms reproduce the very environmental conditions they must live within.

This exceptional capacity to construct their own niche has helped human populations to thrive and grow beyond the natural environmental constraints that have limited other species of organisms.

According to Smith and Zeder, it is the ‘domestication process … that provides the archaeological signature for major human manipulation of terrestrial ecosystems, and the onset of the Anthropocene’. The rise and spread of agricultural societies unleashed a global process of transformative environmental change that continues to this day.

Abundant evidence confirms that agricultural land use was widespread by the mid-Holocene, including deposits of soils and sediments caused by increased soil erosion, charcoal, the remains of crop plants and weeds, including pollen, starch grains, and phytoliths (silica crystals produced in plant cells), the bones and other remains of domestic livestock, changes in the isotopic composition of soils and fossil manures, and long-term changes in vegetation structure and species composition left behind after early land clearing and soil tillage; present-day woodlands from the Mediterranean to the Tropics are increasingly recognized as the bio-cultural legacies of long histories of prior human use. Agricultural land use also produced anthropogenic soils, from the manure-enriched ‘plaggen’ soils of north-western Europe, which may date to 4000 bc, to the ‘terra preta’, or ‘dark earth’ soils enriched with charcoal and waste materials that are observed across the Amazon basin dating perhaps to 500 bc and may also have been produced in Africa, together with various ‘anthrosols’ altered by manuring, tillage, irrigation, and other land use practices in different regions. The widespread presence of anthropogenic soils has been suggested as a golden spike for the Anthropocene, circa 2,000 years ago,

Agricultural transformation of Earth began more than 10,000 years ago and continues to convert natural habitats to agricultural landscapes engineered and managed to support populations of domesticated species (Figure 28). Spreading gradually across the continents over millennia, agriculture began leaving a legacy of altered soil chemistry and sedimentary processes transformed by land clearing, soil tillage, and erosion. Hydrology was altered by reservoirs and irrigation systems. And the functioning of the biosphere, the atmosphere, and the Earth system as a whole began to change.

Ruddiman’s hypothesis compares the ‘natural’ downward trends in atmospheric carbon dioxide and methane observed in prior interglacial intervals with those of the Holocene. Unlike prior interglacials, methane concentrations stopped declining in the mid-Holocene, 5,000 years ago, and began to rise. A similar trend is observable in carbon dioxide as well, starting 7,000 years ago. Ruddiman’s hypothesis ascribes these anomalous trends to greenhouse gas emissions caused by agricultural use of land. In 2011, archaeologist Dorian Fuller used a historical model of rice areas to demonstrate that methane emissions from early rice production could account for about 80 per cent of the early anthropogenic trend in atmospheric methane (Figure 30). Subsequent work using carbon isotopes has confirmed that these early methane emissions were indeed anthropogenic.

Increasingly intensive and productive land use systems evolved in support of ever denser populations. The higher yields of these systems produced agricultural surpluses that were extracted by trade and taxation, enabling the rise of urban populations with increasingly hierarchical and complex societies with specialized roles from artisan to trader to king, and new tools for living in a social world, including money, writing, and metallurgy—the key to new forms of weaponry.

Through trade, warfare, religion, and other social interactions, human societies became increasingly interconnected into ‘world systems’ of exchange. Cultural knowledge, artefacts, natural resources, and living organisms spread rapidly across these world systems, both intentionally as trade goods, and unintentionally as stowaways, including pests and diseases.

Though the ‘Old World’ societies of Eurasia were already interconnected by exchange more than 2,000 years ago, human societies were not yet globally connected, despite their presence on every continent except Antarctica. Increasing European demands for new wealth, power, and influence would change this, by driving an expansion of trading efforts beyond customary routes. Ultimately, more than 500 years ago, these efforts would result in the first substantial two-way exchange of culture and biology between Europe and the Americas. The accidental ‘discovery’ of the Americas by Christopher Columbus set off a process of global social and environmental change like no other before, the Columbian Exchange, through which the Old World and the New World became one. Driven by European efforts to extract wealth from the Americas, human societies were integrated for the first time into a truly global world system of social, material, and biological exchange.

Domestic livestock, from horses (native horses were lost in the Pleistocene extinction), to cattle, to pigs, changed livelihood strategies across the Americas.

Epidemics spread so rapidly through indigenous exchange networks that many native societies were wiped out before Europeans first reached them.

In 2015, an ecologist and a geographer, Simon Lewis and Mark Maslin, in a Nature review of Anthropocene GSSP proposals, also introduced their own: ‘the Orbis spike’ (Figure 31). Orbis, Latin for world, proposed that the Anthropocene was initiated by the Columbian Exchange, in which the ‘collision of the Old and New Worlds’ marked humans as not only a global species, but now also a global system and a global force with geologically unprecedented consequences, including the global interchange and homogenization of Earth’s biota. Moreover, the unprecedented scales of social change, resource extraction, and commercial land use unleashed by Europeans in the Americas ultimately fuelled the development of industrial societies. The emergence of Earth’s first global human system unfolded over hundreds of years, leaving a permanent, though mostly diachronous, record in the global homogenization of flora and fauna together with the usual material evidence of transformative social-environmental change.

The nature of the material record studied by archaeological stratigraphers is especially complex, heterogeneous, and diachronous (Figure 32). It is common for the deposits made by one society, or even just one household, to be reworked by another through the digging of ditches, foundations, and graves, to which are added still further buildings, rubbish, and debris, all of which might later be covered by layers of sediment deposited through flooding and other natural processes, or have been cleared away to begin construction anew. It may show correlations in its depth and composition among the sites produced by a given society, or it may not. It may be pierced in one place by catacombs, deep wells, and subway tunnels, in another, covered by tilled soils, artificial wetlands, a landfill, or a hill composed of multiple layers of settlements laid down one over another over millennia (a ‘tell’, a common archaeological feature in the Middle East). It ranges from non-existent in some places to tens of metres deep in others. At every scale, from site, to region, and especially globally, the archaeosphere is intensely heterogeneous and diachronous. In Edgeworth’s view, and that of archaeologists in general, diachroneity defines not only the archaeosphere, but also the Anthropocene itself.

The one thing that unites all of these proposals is their common focus on recognizing the long, rich, and diachronous history of human transformation of Earth’s environments. The Industrial Revolution and the Great Acceleration are merely the latest, and most impactful, chapters in a long, entangled, and evolving history of human transformation of Earth’s environments; a history that is still unfolding.

ecology as a discipline has been reshaped by the need for new approaches to address the ecology of an Earth transformed by human societies. New paradigms have emerged, redefining the value of nature and the role of humans in shaping and curating the ecology of an increasingly anthropogenic biosphere.

Ecologists, like archaeologists and anthropologists, developed traditions of studying smaller sites and regions, where regional and global interactions of humans and the natural world might be considered external to their studies.

In 1778, Comte de Buffon was already prepared to claim that ‘the entire face of the Earth bears the imprint of human power’. In 1997, ecologist Peter Vitousek and colleagues published a hugely influential Science paper offering evidence ‘that we live on a human-dominated planet’. And the first person to name the Anthropocene was not Paul Crutzen, but lake ecologist Eugene Stoermer.

The famed extinctions of the Dodo and the trees of Easter Island, once attributed solely to overexploitation, are now considered largely the result of introduced species feeding on their eggs and seeds, respectively. More recently, toxic pollutants, including the pesticide DDT, have put species, especially those at the top of the food chain, at risk of extinction. Anthropogenic global climate change is now emerging as what may become the most significant extinction driver of all time, amplifying the already potent mix of anthropogenic pressures behind what is increasingly called Earth’s sixth mass extinction.

Earth’s sixth mass extinction has not yet arrived. Nevertheless, human societies are accelerating extinction rates well beyond their historical baselines, especially for vertebrates. Massive overfishing by factory ships is rapidly reshaping the biodiversity and food chains of entire oceans, defaunating the marine realm in much the same way as our ancestors defaunated Earth’s land. If these rates of species loss are not curtailed, Earth’s six mass extinction and a biosphere drastically reduced in biodiversity will come to define the ecology of the Anthropocene.

In an increasingly anthropogenic biosphere, new relationships are forming. Societies, people, wildlife, and entire ecosystems are co-evolving and co-creating new forms of nature in addition to conserving and restoring those that came before.

Ecologists are increasingly probing the causes and consequences of anthropogenic ecological change and developing new paradigms that embrace the coupling of human and natural systems. In the 1950s, ecologist Eugene Odum highlighted human dependence on ecosystems in the textbook that helped make ecology a household word in the 1960s and 1970s. He also studied ‘old field succession’, the recovery of vegetation on abandoned farmland. Rachel Carson brought an ecologist’s understanding of the widespread consequences of industrial chemicals to the public with Silent Spring in 1962. Ecosystem research in the Hubbard Brook watershed led to the discovery of acid rain in the 1970s. And in 1986, Peter Vitousek went global with his estimate that humans were ‘appropriating’ nearly 40 per cent of Earth’s terrestrial photosynthesis by harvesting forests and using land for agriculture. Before Crutzen’s Anthropocene, Vitousek made the case for an Earth reshaped by humanity in his classic 1997 paper in Science, ‘Human Domination of Earth’s Ecosystems’.

With most of the terrestrial biosphere reshaped by humans, the need for a rich understanding of the global ecological patterns produced by human interactions with ecosystems became clear. In 2007, I worked together with geographer Navin Ramankutty to rectify this by integrating data on human populations, land use for crops and pastures, and vegetation cover to map Earth’s anthropogenic biomes, calling these anthromes (Figure 38). Our data showed that in year 2000, more than 75 per cent of the terrestrial biosphere had been transformed into anthromes, including urban areas and other dense settlements (around 1 per cent of Earth’s ice-free land), agricultural villages (6 per cent), croplands (16 per cent), rangelands (32 per cent), and seminatural lands with only minor human populations and land use (20 per cent), leaving wildlands without human populations or land use in less than one-quarter of the terrestrial biosphere. In later work, we showed that significant areas of anthromes first emerged about 8,000 years ago, and covered more than half of the terrestrial biosphere between 500 and 2,000 years ago, depending on the historical data we used, but this was mostly in the form of seminatural lands. Only in the past century has more than half of the terrestrial biosphere been transformed into the most intensively used urban, village, cropland, and rangeland anthromes.

human and natural systems are globally ‘telecoupled’. As humans continue constructing their niche across the planet, Earth is functioning more and more like a social-ecological system with a social metabolism geared toward sustaining increasingly wealthy and demanding human populations. Already, more than 90 per cent of Earth’s total mammal biomass is composed of humans and domesticated animals.

In the 1920s, ecologists formalized this as ‘carrying capacity’ (K): the environmental limits to a population’s growth in a given environment. When populations grew beyond their carrying capacity, it was argued, a crash was imminent.

In the words of Jason Moore in 2014, the Capitalocene began with ‘a turning point in the history of humanity’s relation with the rest of nature, greater than any watershed since the rise of agriculture and the first cities—and in relational terms, greater than the rise of the steam engine’. Capitalism, not industrialization, caused Earth’s transformation by producing massive social inequalities that supported ‘audacious strategies of global conquest, endless commodification, and relentless rationalization’.

In the January 2016 issue of Science magazine, the AWG (including myself) presented scientific evidence supporting the Great Acceleration of the mid-20th century as the main scientific narrative explaining Earth’s transition out of the Holocene Epoch and into the Anthropocene. Extinctions, deforestation, domestication, species invasions, agriculture, rice farming, anthropogenic soils, and even the Industrial Revolution were all examined and rejected as too diachronous to define a globally synchronous golden spike for the proposed new epoch of the GTS. The AWG also considered and rejected Lewis and Maslin’s Orbis proposal based on the CO2 dip in 1610, for reasons of relative size of the signal and difficulties in global correlation, in the same Science paper and subsequent publications.

Stratigraphers divide geologic time into discrete intervals for purely pragmatic reasons, not because they believe that Earth’s dynamics are not continuous.

efforts to advance scientific understanding of human transformation of Earth are inherently focused not on the identification of precise boundaries in time, but on the complex, continuous, socially differentiated, ecologically connected, and historically contingent processes by which humans have been producing this transformation over time. From

the causes of Earth’s transition to the Anthropocene are human and social.

More than 170,000 ‘synthetic mineral-like substances’, produced only because of human activities, have now been identified, from silicon computer chips to industrial abrasives to ancient ceramics and glass—compared with about 5,000 ‘natural’ minerals.

The 30 trillion tonne mass of this ‘physical technosphere’ is truly staggering: 100,000 times greater than Earth’s living human biomass (but still only one 200 millionth of Earth’s total mass). Plastic materials alone now far exceed human biomass, growing from 2 million tonnes produced annually in 1950 to 300 million in 2015. Total historical production, now 5 billion tonnes, is enough to wrap Earth’s entire surface in a thin layer of plastic film.

the diversity of ‘technospecies’ may exceed the diversity of Earth’s 10 million or so living species. Technospecies of electronic gadgets, household goods, and industrial parts is almost certainly in the many millions.

Vernadsky himself considered human cognition the ‘third stage’ in Earth system development, appearing after the geosphere and the biosphere as a globally conscious ‘noösphere’, based on the concept introduced by the French priest and philosopher Pierre Teilhard de Chardin in the 1920s. Given Earth’s current state, one can only wonder what the noösphere is thinking.

Already, there is evidence that anthropogenic greenhouse gas emissions have delayed Earth’s next glaciation by 100,000 years.

Now, more than 85,000 industrial chemicals are in active use and their production is accelerating (Figure 42). Most have never been tested for harmful effects on humans, let alone other species, or the Earth system as a whole.

If trends continue, ocean plastics will outweigh fish by 2050.

synthetic hormones and other pharmaceuticals are accumulating in freshwater organisms and across entire ecosystems, with relatively unknown consequences.

Given the overwhelming scale, rate, and diversity of harmful global environmental changes produced by human societies, it is hard not to view the Anthropocene as an unmitigated disaster. It might well be viewed as an interval in which humanity, or at least, its wealthiest industrial societies, are driving themselves and the rest of the planet senselessly to ruin.

At this time in which we change the world as we know it, we must also change the way we know the world. The Anthropocene calls on us to think bigger than our individual lives, to imagine the operations of an entire planet and its changes over timescales longer than human societies, from start to finish. It fits in well with broader efforts to reframe education through the lens of ‘Big History’, a curriculum that connects together historical processes and events from the Big Bang to the present and into the future. It opens us to think forward in deep time, like Stewart Brand and Danny Hillis’s Long Now project that is building a clock designed to run for 10,000 years, requiring five-digit years, like 02017.