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Anthropocene
From Wikipedia, the free encyclopedia
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.[2] A large majority of that Stratigraphy Commission decided the proposal had merit and should therefore 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.[3]
Many scientists are now using the term and the Geological Society of America entitled its 2011 annual meeting: Archean to Anthropocene: The past is the key to the future.[4] The Anthropocene has no precise start date, but based on atmospheric evidence may be considered to start with the Industrial Revolution (late eighteenth century).[2][5] 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 believe the human impact has significantly changed (or halted) the growth of biodiversity.[6] 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"[7]:1; this would be closely synchronous with the current term, Holocene.
Etymology
The name Anthropocene is a combination of Greek roots: anthropo- meaning "human" and -cene meaning "new". All epochs in the Cenozoic Era end in "cene".
The biologist Eugene Stoermer originally coined the term but it was independently invented and popularized by Nobel Prize-winning chemist Paul Crutzen. Stoermer wrote, "I began using the term 'anthropocene' in the 1980s, but never formalized it until Paul contacted me".[8] 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."[9] The term was first used in print in 2000 by Crutzen and Stoermer in a newsletter of the International Geosphere-Biosphere Programme.[5] In 2008, Zalasiewicz suggested in GSA Today that an anthropoceneepoch is now appropriate.[2]
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'.[10] 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".[11] 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."[12] 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),[13] 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 word evolved into the Anthropocene, which is generally regarded as being a more suitable technical term.[14]
Nature of human effects
Biodiversity[edit]
Many species have gone extinct due to human impact. Most experts agree that human activities have accelerated the rate of species extinction. The exact rate is controversial, perhaps 100 to 1000 times the normal background rate of extinction.[15] 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 - have declined substantially in the world's oceans over the past century. Since 1950 alone, algal biomass decreased by around 40%, probably in response to ocean warming - and the decline has gathered pace in recent years.[16] Some authors have postulated that without human impacts the biodiversity of the planet would continue to grow at an exponential rate.[6] The implications being that global warming is accelerating due to, or exacerbated by, human activities.
A 13 July 2012 New York Times op-ed by ecologist Roger Bradbury predicted the end of biodiversity for the oceans, saying that the coral reefs are doomed, "Coral reefs will be the first, but certainly not the last, major ecosystem to succumb to the Anthropocene."[17] This op-ed quickly generated much discussion among conservationists and was rebutted on The Nature Conservancy's website, defending its position of protecting coral reefs despite continued human impacts causing reef declines.[18]
Climate
One suspected 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 CO2have increased its atmospheric concentration by a comparable amount from 280 ppm (Holocene or pre-industrial "equilibrium") to approximately 397 ppm.[19] This signal in the Earth's climate system is especially significant because it is occurring much faster,[20] 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).
Trace elements[edit]
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 ofchlorine present in ice cores from 1960s atomic weapon testing programs, as well as a layer of mercury associated with coal plants in the 1980s.
Anthropocene temporal limit
"Early anthropocene" theory[edit]
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.
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.[21][22][23] Ruddiman's work has, in turn, been challenged on the grounds that comparison with an earlier interglaciation ("Stage 11", approximately 400,000 years ago) suggest 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.[24]
That 8,000 years ago the planet sustained a few million people and was still fundamentally pristine,[25] is the basis for an assertion that an early date for the proposed Anthropocene term does not account for a substantial human footprint on Earth.
Industrial Revolution
Crutzen proposed the Industrial Revolution as the start of Anthropocene.[10] Although it is apparent that the Industrial Revolution ushered in an unprecedented global human impact on the planet,[26] much of Earth’s landscape already had been profoundly modified by human activities.[27] Dating of the beginning of a period called Anthropocene therefore ought to be assigned to the moment when humankind 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 Newcomen's 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.
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.[28]
At this time, the Roman Empire encompassed large portions of Europe, the Middle East and North Africa. In China the classical dynasties were flowering. TheMiddle kingdoms of India had already the largest economy of the ancient and medieval world. The Napata/Meroitic kingdom extended over the current Sudanand 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.[29]
Anthropocene marke
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.[30][31]
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.[32] Human activity is now firmly established as the sixth factor of soil formation.[33] 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.[28]
Transition From the Anthropocene
It has been argued that the Anthropocene may transition to an epoch of human stewardship over the environment, a post carbon world.
See also
- Anthropocentrism
- Anthropogenic biomes
- Control of fire by early humans
- Ecocriticism
- Effects of global warming
- Geoengineering
- Holocene extinction
- Planetary boundaries
- Power Down: Options and Actions for a Post-Carbon World
