The Anthropocene: Definition and Legitimacy

The Anthropocene: Definition and Legitimacy as an Epoch

By: Gavin Gleason

Introduction

INDEX

Importance and History

What is the Anthropocene

Contributing Factors

Index containing each section (click access each one individually), use the icon below within each slide to return if you want to skip around the sections.

Sediment and Soil

Climate and Atmosphere

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Plastic

Biosphere

Fallout

Recognition

Anthropocene Working Group

Current Progress

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Conclusion

References

Closing Thoughts

What is the Anthropocene

The Anthropocene is a proposed geological epoch denoting a concept that human activities have terminated the Holocene Epoch and driven modifications to the stratigraphic record that are sufficiently distinct to justify the designation of a new unit. The optimal boundary under evaluation occurs at mid-20th century (1950), known as the "Great Acceleration" reflecting a global transition to an Earth system state where human activities have become the predominant drivers in altering geological archives. Formal adoption relies on the Anthropocene being precisely defined with a globally synchronous base and inception identifiable in the geological record.

Importance & History

• If formally adopted, the Anthropocene would constitute both an abstract geochronological unit of time and a tangible chronostratigraphic unit of geological strata, equivalent to other units in the Geological Time Scale (GTS).

• The term "Anthropocene" was coined by Paul Crutzen in 2000 to describe the realization in the science community that human activities were fundamentally changing the entire Earth System. Originally linked to late 18th century greenhouse gas rises and the Industrial Revolution, continued research showed sharp upward trends in socioeconomic and Earth System signals from the mid-20th century "Great Acceleration" onward, shifting the emphasis for the Anthropocene's onset to the explosive post-1950 growth of human enterprise and impacts.

Climate and Atmosphere

• According to NOAA, the average atmospheric carbon dioxide in 2022 reached a record high of 417.06 parts per million, representing an increase of over 2 ppm for the 11th consecutive year; specifically, at Hawaii's Mauna Loa Observatory, where measurements began in 1958, the 2022 annual carbon dioxide average was 418.56 ppm.

• Based on ice-core data, atmospheric carbon dioxide remained below 300 parts per million for the past 800,000 years until the virtually instantaneous, near 100x faster increase over the last 60 years to over 400 ppm by 2022, far above any historical concentrations.

Sediment and soil

• In the early 20th century, the mechanization of activities like earth removal, mining, terracing, and deforestation led to a detectable global increase in sediment discharge from most major rivers. However, by the 1950s this trend reversed for most rivers as the rapid proliferation of dam construction caused substantial sediment retention. Consequently, from around the 1930s, an imbalance emerged wherein the rate of subsidence exceeded sedimentation in some deltas. Over time, for many deltas this imbalance has become the predominant driver of relative sea-level rise, surpassing even the imprint of global sea level rise attributable to global warming.

• Studies quantitatively confirm that erosion rates from conventionally plowed fields are 1-2 orders of magnitude higher than soil production rates, erosion under native vegetation, and geological erosion over the long term. Plow-based agriculture erosion rates of around 1 mm/per year can erode through soil profiles over the lifetime of civilizations. In contrast, erosion rates under no-till agriculture are much closer to soil production and could enable sustainable farming.

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Plastics take...

Plastic

20-500 years to degrade

• Out of 2.5 billion metric tons of municipal solid waste generated globally in 2010, 275 million metric tons, or 11%, was plastic, according to an estimate based on waste production from 192 coastal countries comprising 93% of the world's population at that time.

based on their substance, structure, and environmental conditions

192 countries produced...

275 million metric tons of plastic

• Microplastics have toxic effects, but can be fully biodegraded by microbes like bacteria, actinobacteria, and fungi that break down pollutants and polymers. Further research into the microbial degradation mechanisms could enable green technologies to remove microplastics from the environment and mitigate their adverse impacts.

in 2010, by the year 2025 this estimate will increase by an order of magnitude

of that plastic...

4.8 to 12.7 million MT

entered the oceans and coastal environments

Biosphere

• Over a relatively brief period, human innovations enabling agriculture and industrialization have increased the global human population and livestock biomass far beyond that of wild mammals. With humans and livestock taking up 0.06 and 0.01 Gt of Carbon and wild mammals taking up 0.007 Gt of Carbon

• The introduction of invasive species has profoundly altered global ecosystems over the past two centuries, leaving a distinct paleontological record in sedimentary deposits. A core sample taken from along the River Thames, contains dense shell assemblages dominated by two invasive bivalves - the Asian clam Corbicula fluminea (arrived 2004) and the zebra mussel Dreissena polymorpha (arrived 1824) - which together account for 96% of the individuals preserved.

Fallout

• Pictured to the right, The Trinity Test was the first test detonation of a nuclear weapon, conducted by the United States Army at the Alamogordo Test Range in New Mexico on July 16, 1945. The test involved exploding an implosion-design plutonium device releasing nuclear energy and creating a mushroom cloud, rising 7.5 miles high into the atmosphere. This test marked the dawn of the nuclear age, establishing nuclear weaponry as a military and political game changer going forward.

• The appearance of plutonium-239, a rare isotope prominent in fallout with a distinct sedimentary profile, marks early 1950s sediments worldwide, making it and other radioactive isotopes potential boundary "golden spikes" to define the Anthropocene, ideally in undisturbed 30-60 degree North latitude lakes or marine layers where fallout peaked.

Athropocene Working Group

In 2008, the potential formalization of the informally-used term "Anthropocene" as a new geological epoch entered initial consideration, prompting the 2009 establishment of an Anthropocene Working Group (AWG). This included not just stratigraphers but climate scientists and others due to the concept's interdisciplinary relevance. However, their fundamental task remained geological – determining if evidence existed for the Anthropocene as a formal chronostratigraphic unit with a globally synchronous lower boundary and utility across earth sciences. Despite the term's broad usage as a conceptual framework, evaluating it against Geological Time Scale criteria requires examination of whether recent anthropogenic changes constitute a distinct unit or mere subdivision of the Holocene based on their degree of alteration to the Earth System evident in stratigraphic archives globally.

Current progress

In August 2016, the Anthropocene Working Group presented interim findings and recommendations at the 35th International Geological Congress in Cape Town, South Africa. This included a summary of evidence assessments and the results of an internal vote gauging perspectives on key questions surrounding the Anthropocene's formalization. The majority view within the Working Group affirms the Anthropocene as stratigraphically legitimate and advocates adoption as a formal epoch/series defined by a mid-20th century lower boundary. Efforts are underway to select an optimal Global boundary Stratotype Section and Point (GSSP) as well as auxiliary reference locations. Potential signatures distinguishable in global sedimentary deposits include anthropogenic radionuclides from nuclear weapons testing appear most viable as a primary marker horizon, while secondary markers could comprise industrial byproducts like plastic and fly ash or carbon isotope profile alterations.

Closing thoughts

The question of whether we're living in a new epoch called the Anthropocene might seem abstract, but it matters. Even if geological timescales don't impact most people's daily lives, the Anthropocene reflects sobering realities about humanity's massive influence on the planet. While it's become associated with climate change and fossil fuels in pop culture, the concept encompasses far more - the full range of environmental changes since humans rapidly expanded our technology and larger society. Adopting the Anthropocene epitomizes the enormity of human activities reshaping the world, especially since the mid-20th century's "Great Acceleration." It's not just about carbon footprints and global warming, but also land use changes, mass extinctions, nuclear fallout, plastics pollution and more. Increased public discussion of humanity's geological-scale impacts can raise awareness and eductate. Even if the minutiae of geological time units seem arcane, they provide perspective for grasping the interconnectedness of climate change alongside other human-driven planetary changes. The Anthropocene offers a framework for considering how best to manage global change going forward for long-term sustainability.

"No one can have had the experience of new discovery, can have witnessed the transmutation of mystery to understanding and order and then to greater mystery, without learning both of our helplessness and our great strength." -J. Robert Oppenheimer

References

1. Zalasiewicz, J., Waters, C. N., Ellis, E. C., Head, M. J., Vidas, D., Steffen, W., et al. (2021). The Anthropocene: Comparing its meaning in geology (chronostratigraphy) with conceptual approaches arising in other disciplines. Earth's Future, 9, e2020EF001896. https://doi.org/10.1029/2020EF001896
2. Climate Change: Atmospheric Carbon Dioxide | NOAA Climate.gov, http://www.climate.gov/news-features/understanding-climate/climate-change-atmospheric-carbon-dioxide (accessed December 2023).
3. Jan Zalasiewicz, Colin N. Waters, Colin P. Summerhayes, Alexander P. Wolfe, Anthony D. Barnosky, Alejandro Cearreta, Paul Crutzen, Erle Ellis, Ian J. Fairchild, Agnieszka Gałuszka, Peter Haff, Irka Hajdas, Martin J. Head, Juliana A. Ivar do Sul, Catherine Jeandel, Reinhold Leinfelder, John R. McNeill, Cath Neal, Eric Odada, Naomi Oreskes, Will Steffen, James Syvitski, Davor Vidas, Michael Wagreich, Mark Williams, The Working Group on the Anthropocene: Summary of evidence and interim recommendations, Anthropocene, Volume 19, 2017, Pages 55-60, ISSN 2213-3054, https://doi.org/10.1016/j.ancene.2017.09.001.
4. Waters, Colin & Syvitski, Jaia & Ga uszka, A. & Hancock, Gary & Zalasiewicz, Jan & Cearreta, Alejandro & Grinevald, Jacques & Jeandel, Catherine & Mcneill, John & Summerhayes, C. & Barnosky, Anthony. (2015). Can nuclear weapons fallout mark the beginning of the Anthropocene Epoch?. Bulletin of the Atomic Scientists. 71. 46-57. 10.1177/0096340215581357.
5. Syvitski James P. M. and Kettner Albert 2011Sediment flux and the AnthropocenePhil. Trans. R. Soc. A.369957–975 http://doi.org.wv-o-ursus-proxy02.ursus.maine.edu/10.1098/rsta.2010.0329
6. Montgomery, D.R., 2007, Soil erosion and agricultural sustainability: Proceedings of the National Academy of Sciences, v. 104, p. 13268–13272, doi:10.1073/pnas.0611508104.
7. Jenna R. Jambeck et al. ,Plastic waste inputs from land into the ocean.Science347,768-771(2015).DOI:10.1126/science.1260352
8. Avinash, G. P., Namasivayam, S. K., & Bharani, R. S. A. (2023). A critical review on occurrence, distribution, environmental impacts and biodegradation of microplastics. Journal of Environmental Biology, 44(5), 655-664. doi:https://doi-org.wv-o-ursus-proxy02.ursus.maine.edu/10.22438/jebM5/MRN-5099
9. Himson, S.J., Kinsey, N.P., Aldridge, D.C., Williams, M., and Zalasiewicz, J., 2020, Invasive mollusc faunas of the River Thames exemplify biostratigraphical characterization of the Anthropocene: Lethaia, v. 53, p. 267–279, doi:10.1111/let.12355.
10. Bar-On, Y.M., Phillips, R., and Milo, R., 2018, The biomass distribution on Earth: Proceedings of the National Academy of Sciences, v. 115, p. 6506–6511, doi:10.1073/pnas.1711842115.

Avinash, G. P., Namasivayam, S. K., & Bharani, R. S. A. (2023). A critical review on occurrence, distribution, environmental impacts and biodegradation of microplastics. Journal of Environmental Biology, 44(5), 655-664. doi:https://doi-org.wv-o-ursus-proxy02.ursus.maine.edu/10.22438/jebM5/MRN-5099 Jenna R. Jambeck et al., Plastic waste inputs from land into the ocean. Science 347, 768-771 (2015). DOI:10.1126/science.1260352

Jan Zalasiewicz, Colin N. Waters, Colin P. Summerhayes, Alexander P. Wolfe, Anthony D. Barnosky, Alejandro Cearreta, Paul Crutzen, Erle Ellis, Ian J. Fairchild, Agnieszka Gałuszka, Peter Haff, Irka Hajdas, Martin J. Head, Juliana A. Ivar do Sul, Catherine Jeandel, Reinhold Leinfelder, John R. McNeill, Cath Neal, Eric Odada, Naomi Oreskes, Will Steffen, James Syvitski, Davor Vidas, Michael Wagreich, Mark Williams, The Working Group on the Anthropocene: Summary of evidence and interim recommendations, Anthropocene, Volume 19, 2017, Pages 55-60, ISSN 2213-3054, https://doi.org/10.1016/j.ancene.2017.09.001. Images from Subcommission on Quaternary Stratigraphy http://quaternary.stratigraphy.org/working-groups/anthropocene/

Zalasiewicz, J., Waters, C. N., Ellis, E. C., Head, M. J., Vidas, D., Steffen, W., et al. (2021). The Anthropocene: Comparing its meaning in geology (chronostratigraphy) with conceptual approaches arising in other disciplines. Earth's Future, 9, e2020EF001896. https://doi.org/10.1029/2020EF001896 Images from Pixabay

Images from: Pixabay

Waters, Colin & Syvitski, Jaia & Ga uszka, A. & Hancock, Gary & Zalasiewicz, Jan & Cearreta, Alejandro & Grinevald, Jacques & Jeandel, Catherine & Mcneill, John & Summerhayes, C. & Barnosky, Anthony. (2015). Can nuclear weapons fallout mark the beginning of the Anthropocene Epoch?. Bulletin of the Atomic Scientists. 71. 46-57. 10.1177/0096340215581357. Images from: Popular Mechanics https://www.popularmechanics.com/military/weapons/a26800527/remastered-archival-video-first-nuclear-weapons-test/ and National Atomic Testing Museum https://nationalatomictestingmuseum.org/2019/07/05/plutonium-ruler-of-the-underworld/

Quote from: 1956: Science and our times Bulletin of the Atomic Scientists, https://thebulletin.org/premium/2020-12/1956-science-and-our-times/ (accessed December 2023).

Jan Zalasiewicz, Colin N. Waters, Colin P. Summerhayes, Alexander P. Wolfe, Anthony D. Barnosky, Alejandro Cearreta, Paul Crutzen, Erle Ellis, Ian J. Fairchild, Agnieszka Gałuszka, Peter Haff, Irka Hajdas, Martin J. Head, Juliana A. Ivar do Sul, Catherine Jeandel, Reinhold Leinfelder, John R. McNeill, Cath Neal, Eric Odada, Naomi Oreskes, Will Steffen, James Syvitski, Davor Vidas, Michael Wagreich, Mark Williams, The Working Group on the Anthropocene: Summary of evidence and interim recommendations, Anthropocene, Volume 19, 2017, Pages 55-60, ISSN 2213-3054, https://doi.org/10.1016/j.ancene.2017.09.001. Figure: Zalasiewicz et al. 2017

Zalasiewicz, J., Waters, C. N., Ellis, E. C., Head, M. J., Vidas, D., Steffen, W., et al. (2021). The Anthropocene: Comparing its meaning in geology (chronostratigraphy) with conceptual approaches arising in other disciplines. Earth's Future, 9, e2020EF001896. https://doi.org/10.1029/2020EF001896 Images from Pixabay

Bar-On, Y.M., Phillips, R., and Milo, R., 2018, The biomass distribution on Earth: Proceedings of the National Academy of Sciences, v. 115, p. 6506–6511, doi:10.1073/pnas.1711842115. Himson, S.J., Kinsey, N.P., Aldridge, D.C., Williams, M., and Zalasiewicz, J., 2020, Invasive mollusc faunas of the River Thames exemplify biostratigraphical characterization of the Anthropocene: Lethaia, v. 53, p. 267–279, doi:10.1111/let.12355. Figure: Himson et al. 2020

Climate Change: Atmospheric Carbon Dioxide | NOAA Climate.gov, http://www.climate.gov/news-features/understanding-climate/climate-change-atmospheric-carbon-dioxide (accessed December 2023). Figure: NOAA Climate.gov

Montgomery, D.R., 2007, Soil erosion and agricultural sustainability: Proceedings of the National Academy of Sciences, v. 104, p. 13268–13272, doi:10.1073/pnas.0611508104. Syvitski James P. M. and Kettner Albert 2011 Sediment flux and the Anthropocene Phil. Trans. R. Soc. A.369957–975 http://doi.org.wv-o-ursus-proxy02.ursus.maine.edu/10.1098/rsta.2010.0329 Figure 1 (Dam Map): Syvitski et al. 2011 Figure 2 (Soil Erosion): Montgomery et al. 2007