'era today - gone tomorrow?

What is the Anthropocene, you ask?

A simple Oxford Dictionary definition states:

'relating to or denoting the current geological age, viewed as the period during which human activity has been the dominant influence on climate and the environment'

As mentioned in my earlier post, the term Anthropocene was coined in 2000 by Crutzen and Stoermer, based on the rationale that humans are having major growing and lasting impacts on Earth's global systems. Though currently informal, the concept of the Anthropocene represents a paradigm shift in global environmental change research (Mackay 2015, in press*). From contributing to mass species extinctions and tearing down entire forests, to drastically altering the composition of the atmosphere, the question prevails: are humans a significant force of nature?

The general gist is that we are in a geological epoch characterised by human ability to modify Earth systems. A key consequence of formalising the Anthropocene is that it would bring an end to our current interglacial epoch of the last 11,700 years, the Holocene. It is yet to be decided if the Anthropocene will join official geologic time alongside other periods like the Pleistocene Epoch (no, not plasticine!) and the Jurassic Period.

The first meeting of the Anthropocene Working Group (Source)

So who gets to make this decision?

The choice is down to 37 highly regarded scientific brains. These people make up the Anthropocene Working Group (AWG), part of the International Commission on Stratigraphy (ICS) Subcommission on Quaternary Stratigraphy. The group, chaired by Jan Zalasiewicz, have some pretty daunting issues to tackle regarding the Anthropocene: should it be established? When would it start? What hierarchical level should it gain in geologic time? So far there isn't really a consensus, but the decision is due to be made in 2016. So, watch this space!

When did the Anthropocene start - if at all? 

Let us take a look at some of the dates in history when humans made their mark...

~13,800 BP: Megafaunal predation & vegetation change 
(Doughty et al 2010)

• Human predation of mammoths led to an expansion of Birch trees
• Increase in Birch pollen across Siberia & Beringia
• Land-surface albedo changed
• Regional rise in temperature of 1°C

11,000-9,000 BP: Initial plant & animal domestication 

(Smith and Zeder 2013)

• Anthropocene should be coeval with the Holocene
• Plant and animal domestication formed the basis for agricultural expansion
• Humans as 'ultimate niche constructors' 

8,000-5,000 BP: Early Anthropogenic Hypothesis 

(Ruddiman 2003, 2013; Ruddiman and Thomson 2001)

• Gradual increase in methane from wet rice agriculture and livestock
• Increased CO2 from preindustrial forest clearance for agricultural expansion
• Both gas increases evident in Greenland ice cores
• Ruddiman argues this activity prevented natural glaciation

2,000 BP: Anthropogenic soils

(Certini and Scalenghe 2011)

• Anthropogenic soil horizons as golden spikes
• Soils show the best record of early civilisations' impact on the environment
• Ploughing, fertiliser use, contamination etc

AD 1750-1800: The Industrial Revolution

(Crutzen and Stoermer 2000; Crutzen 2002; Steffen et al 2007)

• Exploitation and combustion of fossil fuels - allowed the transition to a high energy society
• Rapid industrialisation
• Coincides with James Watt's steam engine design in 1784
• Haber-Bosch fertiliser process revolutionised food production
• Mass population growth
• Ice cores show increases in CO2 and CH4

AD 1610: Orbis

(Lewis and Maslin 2015)

• Meeting of the Old and New Worlds
• Dip in atmospheric CO2 (of 7-10ppm) detectable in ice cores
• Deaths of ~50 million indigenous Americans due to arrival of Europeans
• Irreversible exchange of species across continents
• Regrowth of forests over abandoned agricultural land

AD 1945, July 16th: Trinity

(Zalasiewicz et al 2015)

• First (tentative) conclusion from the AWG
• Age-based (GSSA) boundary from the first atomic bomb in Alamogordo, New Mexico
• Globally identifiable signature in the chemostratigraphic record
• Historical turning point

The Trinity Nuclear Bomb, conducted by the US Army in 1945. A turning point for human and Earth history? (Source)

AD 1950s: The Great Acceleration

(Steffen et al 2007, 2011, 2015)

• Major expansion in human population, economic growth, resource use and technological advances
• Rapid increases in greenhouse gas (GHG) emissions
• CFCs causing a hole in the ozone layer (though the Montreal Protocol of 1987 mitigated this)
• Various markers within this time period (plastics, aluminium, fertilisers, radionuclides)

AD 1964: Nuclear Testing Fallout Peak

(Lewis and Maslin 2015)

• Atomic weapons testing of the 1960s
• Partial Test Ban Treaty in 1963
• 1964 spike in radionuclide fallout in sediments across the planet

I hope that over the course of my blogging there will be new ideas for when this time should begin, perhaps even complete dismissal of existing ideas, and eventually a consensus formed by the working group. 

And now you can relax. PHEW. If you've read all the way through to this point, and you're still interested, massive congratulations. I want YOU to take part in this debate I'll be directing about the Anthropocene! Comment, vote on the poll, and share your thoughts! 

A dose of pun-tastic Anthropocene banter (Source)

'till next time, folks. Let the debate commence.

*Though currently in press, I've had a read of the personal copy of Mackay's chapter in this upcoming book and it is definitely worth a read! The full reference is: Mackay, A.W. (2015) Anthropocene Epoch. International Encyclopaedia for Social and Behavioural Sciences, 2^ndEdition.