Rather than dive straight in at the deep end it is best,
when considering how we’re changing the planet, to start at the beginning and
ask ‘What have we done so far?’. To
do this it is becoming increasingly popular to view the period in which humans
have significantly changed the Earth as the Anthropocene.
First proposed in the early 2000s the notion of a new period of geological
time has often been controversial; some such a William Ruddiman have suggested
that humans began altering the Earth over 8,000 years ago (Ruddiman, 2003). A
more commonly held view is that it is since the 1800s that we have, driven by
the march of industrialisation, truly begun to change the Earth. In 2011 the Anthropocene was very well
summarised by Steffen et al in the
Philosopical Transactions of The Royal Society. I will briefly review this
paper in order to sum up the key concepts of the Anthropocene.
The first thing to note is that the concept of humans
altering the planet is not a new one. Steffen et al point out that since the late 1800s the effect of human
actions on the Earth has been documented, in particular the paper cites
Stoppani’s The Earth as Modified by Human
Action of 1864. What is clear though is that it is only much more recently
that the term Anthropocene was coined, Steffen et al attribute the first use of the it to Eugene Stoermer in the
1980s although when the concept of the Anthropocene was first fully defined is
more vague. Some attribute this definition to Paul Cruzten, a co-author of this
paper (The Economist, 2011).
Steffen et al firmly
reject the ‘early-Anthropocene’ hypothesis as suggested by Ruddiman. It is
acknowledged that human activity has effected natural ecosystems as far back as
‘pre-history’, but to quote directly from the paper early humans were ‘never able to fully transform the ecosystems
around them. They certainly could not modify the chemical composition of the
atmosphere or the oceans at the global level; that remarkable development would
have to wait until the advent of the Industrial Revolution a few centuries
ago’. As this quote suggests the idea that even pre-industrial human
activity such as early fossil fuel use, forest clearance 8,000 years ago or the
development of rice cultivation 5,000 years ago, both events at the centre of the
‘early-Anthropocene’ hypothesis (Ruddiman, 2003) had a significant effect on
the Earth on a global scale is also denied by Steffen et al.
Like others Steffen et
al chose to place the Anthropocene as beginning with the Industrial
Revolution, around the year 1800 (although as is noted, there is no definitive
‘start’ but a transition from agricultural to industrial between 1750 and
1850). Driven by the large scale exploitation of fossil fuels and the ability
to synthesise nitrogen for use as a fertiliser humanity ‘shattered the energy bottleneck’ that had previously contained both
population and activity. Fossil fuel use sky rocketed, coupled with land use
changes and massive releases of greenhouse gases into the atmosphere. By 1850
when the industrial revolution was spreading from England to the rest of the
world humans had finally managed to ‘modify
the chemical composition of the atmosphere or the oceans at the global level’.
Steffen et al use a number of
indicators to track anthropogenic changes to the world’s ecosystems from 1800
onwards. CO2 concentrations in the atmosphere are perhaps the most
direct, showing an increase from 277 to 296ppm in the 150 years following 1750.
However other variables such as urban population, biodiversity loss, water use
and fertiliser consumption (among others) can all be used to track the growing
activity of mankind and its consequences. Analysis of this data leads Steffen et al to the conclusion that after the
Second World War there began a period known as the Great Acceleration. The data in the paper shows that, driven by
post-war technological advances and greater global cooperation in matters of
trade and economic recovery (itself driven by the Bretton Woods accord) almost
every indicator of human development rose exponentially, mirrored by a rise in
the level to which the Earth system was effected by human activity.
As is highlighted in section six of the paper, the nature of
the Anthropocene is now changing. The Great
Acceleration is over, although many of the trends that defined it continue.
What is coming next is conjecture. As Steffen et al observe resource constraints upon fossil fuels will almost
certainly start to check economic growth in the years to come, especially in
the burgeoning, oil and coal dependant economies of Asia. Alongside this the
environmental movement that has grown over the last few decades is now a
serious player in global politics, although getting countries to agree on
emissions reductions in order to curb climate change still proves a difficult task. How effective we are in reducing our
emissions of greenhouse gases in the next few years may well define the nature
of the Anthropocene in the future. It could well be that we enter a third stage
of the Anthropocene, defined by massive changes to the environment around us.
The purpose of this review is however not to delve into the
future of the Anthropocene, that will come in later weeks. Steffen et al have in this paper summed up the
trends within the Anthropocene so far very well and I have tried to highlight
the most important of these trends above. While calling the Anthropocene a new
geological time period may be a step too far it is clear from this paper that
in the context of understanding current climate change the concept of the
Anthropocene is key.
(The paper itself can be found here http://biospherology.com/PDF/Phil_Trans_R_Soc_A_2011_Steffen.pdf)
References:
- · Nb. All quotes and figures not references individually in the text above are drawn from The Anthropocene: conceptual and historical perspectives. Will Steffen, Jacques Grinevald, Paul Crutzen and John McNeil. Phil. Trans. R. Soc. 2011 369. 842-867.
- · The anthropogenic greenhouse era began thousands of years ago; Ruddiman. Climatic Change 61: 261–293, 2003.
- · The Economist, May 2011. http://www.economist.com/node/18741749
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