Origins of the Anthropocene: Once upon a Timeline

Today, I want to travel back in time.

Let’s begin by creating a timeline of possible GSSPs…

~13,800 years BP: Smith and Zeder posit that Megafaunal predation and vegetation occurred around this time. Whilst this possible GSSP has a secondary marker of charcoal in lacustrine deposits, Maslin and Lewis argue that it a specific start date cannot be ratified from this GSSP as this change came about diachronously over 40,000 years. However, it did have both regional and global reach. Globally, 4% of all mammalian species were lost. Different continents and regions were affected on various magnitudes; Africa lost 18%, Eurasia 36%, N America 72%, S America 83% and an astonishing 88% was lost in Australia.

~11,000 years BP: Initial domestication of plants and animals through farming. Whilst the primary marker has been identified as fossil pollen or phytoliths, and auxiliary markers have also been identified, it is hard to pinpoint a GSSA using this GSSP. The advent of origins of farming is too diachronous.

~8,000 years BP: Alternatively, the arrival of extensive farming could be used as a primary marker. This caused CO2 levels to hit a trough in, however, the CO2 record lacks a distinct inflection at this point of time, and thus a GSSA cannot be determined.

5,020 years BP: Methane levels from wet rice agriculture (Fuller et al., 2011) - finally, a GSSP that has a potential date! The lowest value recorded of CH4 in the GRIP ice core, was 5,020 years BP.  This had regional impacts in Southeast Asia, where it originated from, though consequences were seen globally. However, of course, there is an issue… the auxiliary markers of stone axes and fossil domesticated ruminant remains, only provide weak correlations to changes in Earth System processes, and alas, according to Maslin and Lewis, this cannot be used. *Sigh*. Not to worry, we still have a few more to consider, I’m sure we’ll amble across something viable.

~2,000 years BP: Smith and Zeder suggest the alteration of the Earth’s surface by human civilisations, seen through anthropogenic soils. However, a GSSA cannot be determined from anthropogenic soils and they are not very well preserved, faltering on the 7^th criterion of GSSPs.

1610 AD: Migration of large populations to different continents (Europeans to the Caribbean) led to opening of trade networks and the ‘New-Old world collision’. The GSSP global marker was the atmospheric low of CO2 in 1610, shown in the Law Dome ice core. Possible auxiliary markers range from cross-ocean range extensions of the fossil record to decreases in atmospheric methane and changes in pollen and oxygen. These markers all have strong correlations with changes in Earth System processes. Maslin and Lewis term this irreversible commencement of exchange between continents as the ‘Orbis Spike’. So, finally we have seen the first GSSP, which meets all 7 criteria… Hallelujah!

1760 AD to 1880 AD: The Industrial Revolution! When Crutzen and Stoermer termed this new age the Anthropocene, they linked these new anthropogenic changes to Earth’s climatic systems and processes to the start of the industrial revolution. The population began to expand exponentially, leading to rapid urbanisation and industrialisation through the exploitation of fossil fuels. They argue that extensive use of fossil fuels have lead to shifts in the Earth’s atmospheric composition. The primary stratigraphic marker in this instance would be fly ash from coal burning. However, there are so many markers that could be used, none of which provide clear GSSP global markers.

1945 AD: The detonation of nuclear weapons, in particular of the surface Atomic bombs, caused a global spread of artificial radionuclides. Distinct levels of peak radioactivity were captured by stratigraphical markers ranging from ice cores and tree rings to lake/salt marsh sediments and speleothems (cave formations). The clearest and hence the most viable of these to use, as a primary marker is the peak of ¹⁴C recorded in tree rings and glacial ice. Although captured in Northwest Europe, the effects had global reach and auxiliary markers, such as changes in plutonium isotopes, also indicated defined changes in Earth Systems. Meeting all 7 criteria of GSSPs, this can also be seen as a potential GSSP (Yay)!

1950 AD to present: Due to the Great Acceleration, we have increasingly seen the manifestation of persistent industrial chemicals in ice cores, tree rings and sediments. Peaks have been observed in compounds such as sulphur hexafluoride. Steffen et al., proposes the beginning of the Great Acceleration, as the GSSA of the Anthropocene. Below are the graphs observed by Steffen et al., who conclude there is an irrefutable correlation between mid twentieth century socio-economic trends and functions of the Earth System. However, there are so many effects of the Great Acceleration, it is hard to pick just one to represent the GSSP of the Anthropocene; some even consider the spread of radionuclides as a possible GSSP. It is not possible to use peaks in industrial gases and compounds, as they are all far too recent and there may be peaks soon to come!

 

…And that concludes the timeline (thankfully)! As you will probably have noticed, the two possible GSSPs, fulfilling all 7 criteria, are in turquoise – the Orbis spike and the radioactivity from the A-bombs.

So the big debate is ‘Stage vs. Epoch’. Is the Anthropocene a new stage within the Holocene Epoch or is it the Epoch following the Holocene? Whilst I probably won’t be the defining party on this matter, I personally think the tenable GSSPs we have just come across have shown a tremendous shift in the functionings of our Earth! If the Anthropocene is not worthy of a new epoch, surely there shouldn’t be stratotypes to suggest otherwise? So that’s my philosophy on the subject, what’s yours?

Next post, I will be looking at Steffen et al.’s socio-economic trends graph in greater depth, to finally start understanding what the Anthropocene implies for the economy!

Gradstein et al.'s Seven Criteria

Last post I argued that the Anthropocene warranted a new epoch, if and only if, both a GSSP and other auxiliary stratigraphical markers were identified. Zalasiewicz et al. state that these boundaries can be defined by a point of time in the Gregorian human calendar, known as a Global Standard Stratigraphic Age (GSSA). Stratotypes have been widely debated, and thus, so has the dating of the origins of the Anthropocene.

This post notes the 7 necessary GSSP characteristics, proposed by Gradstein et al.. These are:

1.     The global stratigraphical marker i.e. a principal correlation 

Accompanied by…

2.     Auxiliary stratotypes i.e. secondary markers

3.     Evidence of different scales of correlation i.e. regional and global

4.     Adequate depth of complete and continuous sedimentation (both above and below the marker)

5.     An exact location i.e. latitude, longitude, depth/height

6.     Accessibility

7.     Ability to be protected and conserved

Next post will look at possible GSSPs, auxiliary markers, the implied GSSAs, and whether or not they adhere to Gradstein et al.’s criteria.

Defining the Anthropocene

I’m sure by now you can’t help but wonder why there is any need to establish a new geological age. Why can’t we just stay in the Holocene? No one likes change that much… However, the Earth is changing due to human actions, and now that we’ve started it, we can’t seem to stop it.  So come, let’s explore; why is the Earth’s state so drastically different today as opposed to approximately 11,700 years ago?

Mark Maslin and Simon Lewis refer to an epoch as a ‘formal geologic unit of time’. They assert defining a new epoch, requires a global and auxiliary stratigraphical markers (e.g. rock, sediment, or glacier ice). Global markers are known as the Global Stratotype Section and Point (GSSP), and are more commonly referred to as global spikes.

Figure 1

11,700 years before present (BP), the Holocene began. Figure 1 (Maslin and Lewis, 2015), shows the factors that may indicate a new age has arrived. In graph (a), at the Pleistocene-Holocene boundary 11,700 years ago, atmospheric CO₂ reached 260 million ppm. In the formal definition and dating of the GSSP for the base of the Holocene, Walker et al., ratify the golden spike of the Holocene as the agreed compilation of  ‘deuterium excess values, accompanied by more gradual changes in ¹⁸O, dust concentration, a range of chemical species, and annual layer thickness’.

Graphs (b), (c) and (d), also show possible indications of a new age. Graph (b) shows Methane levels from the GRIP ice core reaching a trough 5,020 years ago at just above 550 ppb. Graph (c) shows a pronounced dip in atmospheric CO₂ levels, expressed in the Law Dome ice core. Graph (d) suggests the spread of artificial radionuclides produced by the atomic bombs as a golden spike. It can be seen through the analysis of annual black tree rings, which demonstrate a peak in atmospheric radiocarbon.

Now that I’ve briefly covered the stratigraphy of where the Holocene/Anthropocene debate has originated from, I would like to consider how it is characteristically different. How do we physically notice the stratigraphical changes in the world today? Ian Sample begins by helping us understand what the Holocene is.

The Holocene marked the beginning of an interglacial period, and the end of a glacial ice age, the Pleistocene. It largely refers to the onset of warmer and wetter climatic conditions, also encompassing global growth and impacts of Homo sapiens and technology. As the Holocene incorporates the effect of human activity, there is widespread debate as to whether a defined new age is necessary.

The Anthropocene however, focuses more solely on the significance of human impacts. It regards human activity as a force of nature. We now live in a world such that human activity is as natural a process as volcanic eruptions and earthquakes. It is inescapable, indispensible, and intricately critical to our way of living and the economies we depend so heavily on. An article in The Economist asserts that the Anthropocene will produce fossils containing compilations of materials, previously unseen in the geological record. The Anthropocene fossil record will thus show ‘a planetary ecosystem homogenised through domestication’. There will also be some organisms that are no longer seen, as they are now extinct, due to failure to adapt to such a human-dominated world.

I personally think there is a need to define a new age to encompass the extent to which human activity is influencing the natural foundation our world is built upon. Would you agree? Feel free to comment with your opinion!

Next post I will be looking at the disputed origins of the Anthropocene in more detail, focusing on the more human factors, which will (hopefully) provide a firm base to analyse the economic impacts of this new geological epoch. So please, stay tuned… it’s about to get very interesting!

Setting the AnthropoScene

Before delving into the content of this blog, in this first post, I would briefly like to explain what this blog aims to entail and why I think it is a topic worth exploring.

The coining of the term 'Anthropocene' originated from a publication by Paul J. Crutzen and Eugene F. Stoermer. The Oxford Dictionary defines the Anthropocene as ‘relating to or denoting the current geological age, viewed as the period during which human activity has been the dominant influence on the climate and the environment’. The notion of this new epoch is due to be formally ratified by the International Commission on Stratigraphy, with a target date of 2016. Anson Mackay refers to a golden spike, which marks the end of one geological era and the beginning of another. These are most commonly distinct, sharp vicissitudes of biological fossils or sedimentology.

In the following posts, I shall set the scene for my blog by discussing these questions:

1. What is an epoch?
2. What is the Anthropocene?
3. How does it differ from the age of the Holocene?
4. What are the most widely debated golden spikes?

The beginning of the Anthropocene and its effects on Earth are widely debated. Not many understand the implications of a new age. We cannot remain ignorant to the future that is knocking on our door. As an Economic Geographer, my hope is to hone in on the less explored aspect of this new age: the global and local economy.

Here's some food for thought until my next post. Enjoy :) 

Before It’s News   (top left)

Planet Under Pressure   (bottom right)