The Anthropocene

By: Isabela Claret Torres, MSc, Ph.D.

What is the Anthropocene?

The Anthropocene is a period of time during which human activities have impacted the environment enough to constitute a distinct geological change. This includes, but is not limited to current and ongoing climate change.

Today we have to travel to the past to understand our present. But before we travel the memory lane I have to talk a little about lake sediments. Everything that enters a lake or is produced within a lake settles and becomes integral part of the sediments. Consequently, sediments are archives of the lake, watershed and even the earth history. To study past conditions through the sediment of lakes is necessary to take a sediment core that is sliced in cm and then can tells us a lot about what happened around or far away from this lake in recent or distant periods of times. 

But let’s go back to the main topic of this article. And for that we must travel the memory lane. For some will be a long trip and to others a very short one. Remember at school in our geography class that we had to learn about chronostratigraphic chart (International Commission on Stratigraphy) with the Eons, Eras, Periods, Epochs and Ages? Ok for many I might be talking Greek but everyone have heard of the Jurassic period or the Paleozoic Era. So it does not seem so strange. So right now the earth is on the Phanerozoic Eon, Cenozoic Era, Quaternary Period, Holocene Epoch. But some scientist came up with a different proposition. 

Climate Change

Waters and colleagues in a scientific article published on Science in 2016 proposed that human beings changed so much the earth, water, land and atmosphere that we are in a new Epoch called the Anthropocene. The world derives from the Greek, Anthropo meaning “men” and cene meaning “new”. The term Anthropocene was coined by popular by biologist Eugene Stormer and chemist Paul Crutzen in 2000, but just recent in this article strong evidence shows that humans changed so much the earth that we are probably in a new Epoch the Anthropocene.  

And how did they came out with this conclusion? Using cores of lakes from the arctic and many regions of the world they found human markers in the sediments totally different from past earth conditions. 

In the article the authors linked the signatures with multiple human forces like accelerated technological development, rapid growth of the human population, and increased consumption of resources. With a consequence we have the increase of use of fossil fuels, metals, minerals, and agricultural fertilizers. And all these markers were found in the sediments showing we are in a new Epoch that is distinct from the Holocene.  

Industrial Revolution & Climate Change

The start of this new Epoch is marked by the spread of agriculture and deforestation, the industrial revolution at approximately 1800 and the mid-20^th century great acceleration of the population growth and industrialization.  

Waters et al. (2016) reported that “recent anthropogenic deposits contain new minerals and rock types, reflecting rapid global dissemination of novel materials including elemental aluminum, concrete, and plastics that form abundant, rapidly evolving “technofossils.”. Besides that, “fossil fuel combustion has disseminated black carbon, inorganic ash spheres, and spherical carbonaceous particles worldwide, with a near-synchronous global increase around 1950”. Other anthropogenic pressures included erosion caused by deforestation, road construction and the use of concrete. Geochemical signatures in the sediment include elevated levels of polyaromatic hydrocarbons, polychlorinated biphenyls, and pesticide residues, as well as increased ^207/206Pb ratios from leaded gasoline, starting between~1945 and 1950.

Soil Quality

Waters et al. also stated that “soil nitrogen and phosphorus inventories have doubled in the past century because of increased fertilizer use, generating widespread signatures in lake strata and nitrate levels in Greenland ice that are higher than at any time during the previous 100,000 years”. The influx of nitrogen and phosphorus into lakes is leading many lakes to have eutrophic conditions which I will explain the process in a future article. Other important marker found in sediments all around the world is the excess o ¹⁴C, ²³⁹ Pu and ¹³⁷ Cs due to the detonation of the Trinity atomic devices at Alamogordo New Mexico on 16 of July 1945. And finally atmospheric CO₂ and CH₄ concentrations depart from Holocene and even Quaternary patterns starting at ~1850, and more markedly at ~1950. 

The authors conclude the article as follows: “These novel stratigraphic signatures support the formalization of the Anthropocene at the epoch level, with a lower boundary (still to be formally identified) suitably placed in the mid-20th century. Formalization is a complex question because, unlike with prior subdivisions of geological time, the potential utility of a formal Anthropocene reaches well beyond the geological community. It also expresses the extent to which humanity is driving rapid and widespread changes to the Earth system that will variously persist and potentially intensify into the future.” 

Changing Ecosystems

The message that we take from this article is simple. Humans are changing the earth dynamics and ecosystems functioning we are leaving our mark behind in our lakes sediments, in the arctic and other parts of the world. Maybe in the future scientist will study our time through lakes sediments, and I leave a question: what type of marks we want to leave in the sediments from our generation? Plastic, pollutants? It’s time to change and make a new history in our life time, leaving better sediment markers for the future.  

Source:  

Waters, C.N., Zalasiewicz J., Summerhayes C., Barnosky A.D., Poirier C., Gałuszka, A., Cearreta, A., Edgeworth M., Ellis E.C., Ellis M., Jeandel C., Leinfelder, R., McNeill, J.R., deB Richter D., Steffen, W., Syvitski J., Vidas D., Wagreich M., Williams M., Zhisheng A., Grinevald J., Odada E., Oreskes N. Wolfe A.P. 2016. The Anthropocene is functionally and stratigraphically distinct from the Holocene. Science, 351(6269): 137-148.