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A single species, humans, have gained the capacity to cause major changes on Earth. Ancient and recent human-driven biological, chemical and physical changes to the Earth system are profound, distinct, and ever-increasing. These and many other lines of globally-distributed and stratigraphically significant anthropogenic evidence, argue the need for defining this period of human-dominated Earth as an entirely new geological period – The Anthropocene.
Today, there is little doubt that we live in a human-dominated world.
In 2000, the Dutch chemist, Paul Crutzen (best known for his research on stratospheric Ozone depletion for which he won the Nobel Prize in 1995) and the University of Michigan limnologist, Eugene Stormer (best known for his research on the changing composition of freshwater diatoms as biosphere’s paleorecords), proposed the concept of “The Anthropocene”. Anthropocene was meant to denote the ever-increasing influence of humans on the Earth (“Anthro” for “man”, suggesting “human-influenced”, and “Cene” for “new”, the standard suffix for “epoch” in geological time). They came to this conclusion after noting that the exploitation of Earth’s resources has been astounding as a consequence of the 10-fold increase in human population just over the past 3 centuries. The word “Anthropocene” has now entered the scientific and popular literature as a vivid expression of the degree of the human-driven environmental change on Earth. A big challenge for the International Committee on Stratigraphy (ICS) is to develop an evidence-based definition and a timeline of the Anthropocene. In the next year or so, the ICS will decide if the Anthropocene will be an Age within the current post-glacial Holocene Epoch or a whole new Epoch into itself, and recommend a start date for the newest geological timeline.
Evidence for a new geological time period that marks the impact of humans on Earth is now overwhelming. Humans have left plentiful records of their anthropogenic byproducts in the air, water, ice and sediments - including pollen in lake sediments from agricultural crops, green house gas bubbles in polar ice, post-combustion particles from fossil fuels in sediments, and fall out of radioactive elements globally from atom bomb tests (Figure 1). Our large-scale agricultural heritage traces back about 6000 years, and there is mounting evidence that early agriculture and the generation of greenhouse gasses associated with it may have contributed to significant preindustrial warming of Earth’s climate. The Industrial Revolution fueled by fossil fuels has been running for about the last three centuries, dramatically increasing our capacity for extraction of resources and resulting in massive increases in food production and population. More recently, radioactivity from atomic bomb testing during the middle of the last century, has changed the isotopic ratio of the atmosphere in the short term (decades), and has penetrated the global oceans over the longer term (centuries). Additionally, long-lived plutonium radioisotopes derived from atom bomb fallout have left distinctive time signatures in tree rings, corals and sediments around the globe that will last for thousands of years. Due largely to domestication and global commerce, the abundance and distribution of Earth’s plant and animal communities today are very different from communities that preceded large-scale human activity. Also, the last 100 years is characterized by unprecedented build up of anthropogenic greenhouse gases in the atmosphere. Today, humans are a geological force impacting all of the Earth’s systems including the climate system: e.g., deforestation, agro industry, large dams, mining, fossil fuel extraction, cement manufacturing, shipping and transportation. Altogether, human activities have already massively altered Earth’s landscapes, inland waters, oceans, atmosphere, cryosphere and ecosystems, leaving behind a stratigraphically significant record that will be discernable for millennia from today.
Figure 1. Author-drawn schematic common curve of the coupled increase in human population size (in billions of people; note non-linear axis) and the change in global atmospheric composition (carbon dioxide in parts per million) since the last glacial retreat, highlighting major milestones in humanity’s recent history that have had significant and globally distributed anthropogenic impacts. Although humans have altered the surface of the Earth over the last 80,000 years beginning with hunter-gatherers, globally wide-spread human impact is clearly discernible only since the beginning of agriculture about 6,000 years ago, and the industrial revolution about 275 years ago – both of which enabled rapid and unprecedented increases in food production and population. While it is commonly accepted that we are in the Anthropocene today, it has been a challenge to determine it’s exact start date (brown arrows under the x-axis and clear arrows along the population-CO2 curve). The source for the upper left inset photo on “Anthropocene” showing 12 examples of the many visibly dramatic anthropogenic impacts on Earth is “The Encyclopedia of Earth” (http://www.anthropocene.info). The source for the lower left inset photo documenting the distinct sedimentary record of the Anthropocene in a sediment core from a lake in west Greenland highlighting the transition from glacial sediments into more recent nonglacial organic matter (white dotted line) that include novel presence of anthropogenic fly ash, metals, radioactive isotopes, pesticides, plastics, reactive nitrogen, pollen from agricultural crops, etc., is Waters et al. 2016 (Science). Possible proposed start dates for the Anthropocene range from 6,000 years ago when large-scale agriculture began, ~275 years ago when the Industrial Revolution began (the AgroIndustrial Revolution that gave rise to the factory system and industrial-scale production of food), to as recent as mid-last century when atom bomb tests left global signatures of their radioactive fallout throughout the planet – in sediments and the ocean water masses. Other questions remain such as whether the Anthropocene is to be designated a separate Epoch following the Holocene, or it is to be a Stage or Age within the Holocene Epoch – although consensus is beginning to emerge that the Anthopocene is to be a distinct Epoch into itself. Please note that the x-axis is non-linear.
Not since the cyanobacteria first released oxygen into the atmosphere in Earth’s early history has any single species or group of organisms had such a globally significant impact as humans have. About 2.5 billion years ago, cyanobacteria dramatically changed the chemistry of the atmosphere and oceans by oxygenating them, and caused mass extinction of anaerobic organisms on a planetary scale. Changes of a similar magnitude are being caused by humanity today all across the planet starting with the change in the composition of the atmosphere. The human footprint is everywhere we look. One of the big differences between humans and cyanobacteria, is that we are actually aware of what we are doing. We are now the “self-aware drivers” of global change on a scale that is unparalleled in Earth’s history. With it comes great responsibility to ourselves, the myriad of other planetary inhabitants, and the global commons – air, water and soil. A sound knowledge base, and good governance will be key to wise stewardship of the only home we have. Ready or not, the age of humans is upon us.
Crutzen, P. J., Stoermer, E. F. 2000. The “Anthropocene”. Global Change Newsletter. International Geosphere Biosphere Program 41: 17-18.
Dean, J. R., Jeng, M. J., Mackay, A. W. 2015. Is there an isotopic signature of the Anthropocene? The Anthropocene Review. 1-12.
Dietl, G. P. 2015. Different worlds. Nature. 529: 29.
Edwards, L. E. 2016. What is the Anthropocene? Eos. 97 (2): 6-7. doi:10.1029/2015EO040297.
Kerr, R. A. 2013. Humans fueled global warming millennia ago. Science. 342: 918.
Lewis, S. L., Maslin, M. A. 2015. Defining the Anthropocene. Nature. 519: 171-179.
Monasersky, R. 2015. The Human Age. Nature. 519: 144-147.
Ruddiman, W. F., et al., 2016. Late Holocene climate: Natural or anthropogenic? Reviews of Geophysics. doi: 10.1002/2015RG000503.
Stanley, S. 2016. Early agriculture has kept Earth warm for millennia, Eos. 97 (5): 27, doi:10.1029/2016EO043793
Waters, C. N., et al., 2016. The Anthropocene is functionally and stratigraphically distinct from the Holocene. Science. 351: 137.
Welcome to the Anthropocene
A Man-made world
In search of the Anthropocene Epoch
Working Group On The 'Anthropocene'
Age of Man
What is the Anthropocene and Are We in It?
Human impact has pushed Earth into the Anthropocene, scientists say
Adventures in the Anthropocene
The editor wishes to thank the journal Science for permission to reproduce a figure from Waters et al. 2016.
Félix Pharand-Deschênes at Anthropocene.info and Globaïa kindly granted permission to reproduce the mosaic in Figure 1. The following photographers contributed to the mosaic:
Jean-Daniel Echenard, Flickr
Mike Behnken, Flickr
Henning Mühlinghaus, Flickr
Louis Vest, Flickr
Rainforest Action Network, Flickr
Meena Kadri, Flickr
Climate Action Network International, Flickr
Bo Eide, Flickr
Deepwater Horizon Response, Flickr
Ian Joughin, Imaggeo
Ian Armstrong, Flickr