Anthropocene

Holocene Epoch
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Holocene
Preboreal (10.3–9 ka) Boreal (9–7.5 ka) Atlantic (7.5–5 ka) Subboreal (5–2.5 ka) Subatlantic (2.5 ka–present)

The Anthropocene is a proposed epoch that begins when human activities started to have a significant global impact on Earth's geology and ecosystems. Neither the International Commission on Stratigraphy nor the International Union of Geological Sciences has yet officially approved the term as a recognized subdivision of geological time.

The term "Anthropocene"—which appears to have been used by Soviet scientists as early as the 1960s to refer to the Quaternary, the most recent geological period—was used with a different sense in the 1980s by ecologist Eugene F. Stoermer and has been widely popularized by atmospheric chemist Paul J. Crutzen, who regards the influence of human behavior on Earth's atmosphere in recent centuries as so significant as to constitute a new geological epoch for its lithosphere. A January 2016 paper in Science investigating 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 distinct geological epoch from the Holocene.

In 2008 a proposal was presented to the Stratigraphy Commission of the Geological Society of London to make the Anthropocene a formal unit of geological epoch divisions. A large majority of that Stratigraphy Commission decided the proposal had merit and should be examined further. Steps are being taken by independent working groups of scientists from various geological societies to determine whether the Anthropocene will be formally accepted into the Geological Time Scale.

Nevertheless, many scientists are now using the term "anthropocene", and the Geological Society of America entitled its 2011 annual meeting: Archean to Anthropocene: The past is the key to the future. The Anthropocene has no agreed start date, but some scientists propose that, based on atmospheric evidence, it may be considered to start with the Industrial Revolution (late eighteenth century). 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 controversial; some scientists think the 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 to 15,000 years before present, based on lithospheric evidence; this has led other scientists to suggest that "the onset of the Anthropocene should be extended back many thousand years"; this would be closely synchronous with the current term, Holocene.

In January 2015, 26 of the 38 members of the International Anthropocene Working Group published a paper suggesting that the Trinity test on July 16, 1945, was the starting point of the proposed new epoch. However a significant minority supports one of several alternative dates. In March 2015, a paper published in Nature suggested either 1610 or 1964 could be the beginning of 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.

The Anthropocene Working Group plans to meet in mid-2016 to submit evidence and decide whether the Anthropocene is a true geologic epoch. The proposal is set to be reviewed by the International Commission on Stratigraphy later in 2016. Should it be approved there, the proposal to adopt the term will have to be ratified by the International Union of Geological Sciences before its formal adoption as part of the geologic time scale.

Etymology

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The name Anthropocene is a combination of Greek roots: anthropo- (Greek: ἄνθρωπος ) meaning "human" and -cene meaning "new". All epochs in the Cenozoic Era end in "-cene".

While the biologist Eugene Stoermer is often credited with coining the term, it was in geological informal usage in the mid-1970s. Paul Crutzen independently re-invented and popularized it. Stoermer wrote, "I began using the term 'anthropocene' in the 1980s, but never formalized 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." The term was first used in print in 2000 by Crutzen and Stoermer in a newsletter of the International Geosphere-Biosphere Programme. In 2008, Zalasiewicz suggested in GSA Today that an anthropocene epoch is now appropriate.

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'. A similar term, Homogenocene (from Ancient Greek: homo-, same, Ancient Greek geno-, kind, kainos-, and -cene, new [period]), was first used by Michael Samways in his editorial article in the Journal of Insect Conservation (1999) entitled, "Translocating fauna to foreign lands: here comes the Homogenocene". Samways used the term to define our current geological epoch, in which biodiversity is diminishing and ecosystems around the globe become more similar to one another. The term was used by John L. Curnutt in 2000 in Ecology, in a short list entitled, "A Guide to the Homogenocene." Curnutt was reviewing Alien species in North America and Hawaii: impacts on natural ecosystems by George Cox. Andrew Revkin coined the term Anthrocene in his book Global Warming: Understanding the Forecast (1992), in which he wrote, "we are entering an age that might someday be referred to as, say, the Anthrocene. After all, it is a geological age of our own making." The name evolved into "the Anthropocene", which presents itself as a more suitable technical term.

Nature of human effects

Main article: Human impact on the environment

Biodiversity

Main article: Holocene extinction

Earth at night, a composited night-time image of the world during the Anthropocene

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. In 2010 a study published in Nature found that "marine phytoplankton – the vast range of tiny algae species accounting for roughly half of Earth's total photosynthetic biomass – had 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. – implying that human activities accelerate or exacerbate global warming.

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 13 July 2012 New York Times op-ed 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 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 impacts on food webs worldwide.

Biogeography

Permanent changes in the distribution of organisms from human influence will be identifiable in the geologic record. Many species have been documented moving into regions that were once too cold for them, often at rates faster than initially expected. This has occurred in part as a result of evolving climate, but also in response to farming and fishing, and the accidental introduction of non-native species to new areas by 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.

Climate

Main article: Anthropogenic climate change

One geological symptom resulting from human activity is increasing atmospheric carbon dioxide (CO₂) content. During the glacial–interglacial cycles of the past million years, natural processes have varied CO₂ by approximately 100 ppm (from 180 ppm to 280 ppm). As of 2013, anthropogenic net emissions of CO₂ have increased its atmospheric concentration by a comparable amount from 280 ppm (Holocene or pre-industrial "equilibrium") to approximately 397 ppm. This signal in the Earth's climate system is especially significant because it is occurring much faster, and to an enormously 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 are the result of cement production and land-use changes (e.g. deforestation).

Geomorphology

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.

Stratigraphy

Sedimentological record

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 very many rivers around the world mean the rates of sediment deposition in any given place do not always appear to increase in the Anthropocene. For instance, many deltas around the world are actually currently sediment starved by such dams, and are subsiding and failing to keep up with sea level rise, rather than growing.

Fossil record

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 manmade artifacts preserved in stratigraphy are known as "technofossils".

Changes in biodiversity will also be reflected in the fossil record, as will species introductions.

Trace elements

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 1960s atomic weapon testing programs, as well as a layer of mercury associated with coal plants in the 1980s. 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 14C, 239Pu, and other artificial radionuclides. The concentrations of such radionuclides peaks in 1964, 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.

Anthropocene temporal limit

"Early anthropocene" model

Main article: Early anthropocene

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.

This period (10,000 years to present) is usually referred to as the Holocene by geologists. For the majority of the Holocene, human populations were relatively low and their activities considerably muted relative to that of the last few centuries. Nonetheless, many of the processes currently altering the Earth's environment were already occurring during this period. Concerning the best starting date for the Anthropocene many proposals have been advanced. From the past to present, some authors consider the Anthropocene and the Holocene to be the same or coeval geologic time span, others that the onset of the Anthropocene was just a bit more recent. In fact, arguing the early Anthropocene hypothesis, William Ruddiman claims that the Anthropocene, as defined by significant human impact on greenhouse gas emissions, began not in the industrial era, but 8,000 years ago, as ancient farmers cleared forests to grow crops. Ruddiman's work has, in turn, been challenged on the grounds that comparison with an earlier interglaciation ("Stage 11", approximately 400,000 years ago) 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. Ruddiman argues, in rebuttal that, this results from an invalid alignment of recent insolation maxima with insolation minima from the past, among other irregularities, which invalidate the criticism. 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 and was still fundamentally pristine, is the basis for an assertion that an early date for the proposed Anthropocene term does account for a substantial human footprint on Earth.

Antiquity

A 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 Subatlantic.

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 large areas of northern Peru. Although often apart from each other and intermixed with buffering ecosystems, the areas directly impacted by these civilizations and others were large. Additionally, some activities, such as mining, implied much more widespread perturbation of natural conditions.

Industrial Revolution

Crutzen proposed the Industrial Revolution as the start of Anthropocene. 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. Dating of the beginning of a period called Anthropocene therefore ought to be assigned to the moment when mankind joined with the other environmental forces in shaping the planet. Doing so is difficult; perhaps it is even unrealistic to identify a Year Zero of an Anthropocene era. In fact, the human impact on Earth has grown progressively, with few substantial slowdowns. Lovelock proposes that the Anthropocene began with the first application of the Newcomen atmospheric engine in 1712. Until then, the highest level of energy available throughout human history had been limited to 1 kW per square metre, from the sun.

Anthropocene marker

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 fertilizers, 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 should be hence 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 Anthropocene in culture

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 prompts questions about death and the ends of civilization, memory and archives, the scope and methods of humanistic inquiry, and emotional responses to the "end of nature". It has been also criticized as an ideological construct.

See also

• Anthropocentrism
• Anthropogenic biomes
• Control of fire by early humans
• Ecocriticism
• Effects of global warming
• Climate engineering
• Great Transition
• Holocene extinction
• Planetary boundaries
• Power Down: Options and Actions for a Post-Carbon World
• The Sixth Extinction (book)

External links

• Working Group on The 'Anthropocene', International Commission on Stratigraphy (ICS)
• "The Anthropocene", copy of original International Geosphere-Biosphere Programme article on Crutzen's website, May 2000.
• "The Anthropocene Debate: Marking Humanity’s Impact", by Elizabeth Kolbert, Yale Environment 360, May 17, 2010
• "Anthropocene", Encyclopedia of Earth
• Welcome to the Anthropocene Website
• Aarhus University Research on The Anthropocene (AURA)
• The Anthropocene Project at Haus der Kulturen der Welt, Berlin
• The Advent of the Anthropocene: Was That the Big Story of the 20th Century? (audio lecture)

External video
Welcome to the Anthropocene – YouTube