The Anthropocene: a new epoch of geological time? INTRODUCTION

Abstract

Anthropogenic changes to the Earth's climate, land, oceans and biosphere are now so great and so rapid that the concept of a new geological epoch defined by the action of humans, the Anthropocene, is widely and seriously debated. Questions of the scale, magnitude and significance of this environmental change, particularly in the context of the Earth's geological history, provide the basis for this Theme Issue. The Anthropocene, on current evidence, seems to show global change consistent with the suggestion that an epoch-scale boundary has been crossed within the last two centuries.

Full text

doi: 10.1098/rsta.2010.0339 , 835-841369 2011 Phil. Trans. R. Soc. A
Jan Zalasiewicz, Mark Williams, Alan Haywood and Michael Ellis
time?
The Anthropocene: a new epoch of geological
References html#ref-list-1
http://rsta.royalsocietypublishing.org/content/369/1938/835.full.
This article cites 22 articles, 15 of which can be accessed free
Rapid response 1938/835
http://rsta.royalsocietypublishing.org/letters/submit/roypta;369/
Respond to this article
Subject collections
(26 articles)geochemistry  (81 articles)climatology  (30 articles)oceanography 
collections
Articles on similar topics can be found in the following
Email alerting service herein the box at the top right-hand corner of the article or click
Receive free email alerts when new articles cite this article - sign up
http://rsta.royalsocietypublishing.org/subscriptions
go to: Phil. Trans. R. Soc. ATo subscribe to
This journal is © 2011 The Royal Society
on February 2, 2011rsta.royalsocietypublishing.orgDownloaded from

Phil. Trans. R. Soc. A (2011) 369, 835–841
doi:10.1098/rsta.2010.0339
INTRODUCTION
The Anthropocene: a new epoch of
geological time?
BYJAN ZALASIEWICZ1,*, M ARK WILLIAMS1,2 ,ALAN HAYWOOD3
AND MICHAEL ELLIS2
1Department of Geology, University of Leicester, Leicester LE1 7RH, UK
2British Geological Survey, Keyworth, Nottingham NG12 5GG, UK
3School of Earth and Environment, University of Leeds, Leeds LS2 9JT, UK
Anthropogenic changes to the Earth’s climate, land, oceans and biosphere are now so
great and so rapid that the concept of a new geological epoch defined by the action
of humans, the Anthropocene, is widely and seriously debated. Questions of the scale,
magnitude and significance of this environmental change, particularly in the context of
the Earth’s geological history, provide the basis for this Theme Issue. The Anthropocene,
on current evidence, seems to show global change consistent with the suggestion that an
epoch-scale boundary has been crossed within the last two centuries.
Keywords: Anthropocene; environmental change; human influence; geological time
1. Introduction
From the late nineteenth century, scientists were becoming aware of the extent
of human influence on planet Earth. George Perkins Marsh’s influential Man and
Nature [1] is perhaps the first major work to focus on anthropogenic global change,
while the Italian geologist Antonio Stoppani [2] coined the term ‘Anthropozoic’
to denote the time of this transformation. As the nineteenth century drew to
a close, Svante Arrhenius [3] and Thomas Chamberlain [4] were exploring the
relationship between CO2concentrations in the atmosphere and global warming.
Arrhenius suggested that future generations of humans would need to raise
surface temperatures to provide new areas of agricultural land and thus feed a
growing population. In 2002, the Nobel Prize-winning atmospheric chemist Paul
Crutzen [5] resurrected the concept of the Anthropocene to denote the current
interval of time on Earth in which many key processes are dominated by human
influence. The word quickly entered the scientific literature as a vivid expression of
the degree of environmental change on Earth caused by humans, and is currently
under discussion as a potential formal unit of the geological time scale [6,7].
*Author for correspondence (jaz1@le.ac.uk).
One contribution of 13 to a Theme Issue ‘The Anthropocene: a new epoch of geological time?’.
This journal is ©2011 The Royal Society835
on February 2, 2011rsta.royalsocietypublishing.orgDownloaded from

836 J. Zalasiewicz et al.
2. What characterizes the Anthropocene?
The use of tools was once thought to distinguish humans from all other animals,
and among the earliest people who lived at 2 Ma in Africa were Homo habilis,
the ‘handy man’. From that time, people have been modifying the Earth. For
much of that human story, these changes were achieved by muscle and sinew,
supplemented first by primitive tools, largely for hunting, and later by fire.
Traces of humans in the Pleistocene rock record are rare, and stay rare until
the Holocene.
The influence of humans is felt more strongly towards the end of the Pleistocene
epoch, with the demise of much of the ‘megafauna’ that included the sabre-
toothed cats in North America or the woolly mammoths of Siberia. On many
continents, the disappearance of the megafauna appears to coincide with the
arrival of modern humans. Like many events in the geological record, this
extinction is diachronous—that is, happening in different places at different
times. Thus, the megafauna disappeared in Australia 50 000 years ago, but in
the Americas 13 000 years ago. Yet, the megafauna are still living in parts of
Africa and South Asia, albeit under threat nearly everywhere.
From the beginning of the Holocene, about 11 500 years ago, evidence for
human activities becomes more widespread, with the rise of agriculture beginning
first in the ‘fertile crescent’ of the Middle East and gradually extending to
northern Europe by 6000 years ago [8]. This change from hunting to cultivation
leaves a clear fossil record in the pollen preserved in sedimentary successions
through this interval. And, the clearance of forests, associated with the rise of
agriculture, may have begun to elevate CO2levels in the atmosphere long before
the Industrial Revolution [8].
Following the Neolithic revolution of agriculture, humans began to live in
villages and towns, and by the third millennium BC the cities of ancient
Mesopotamia, the Nile Valley and the Indus Basin of Pakistan were well
established and culturally distinctive. Still later, urban cultures spread across
the tropical and temperate zones everywhere, with those in Europe, Central and
South America and China being diverse and advanced by the first millennium
BC. This rate of urbanization has accelerated through time, with the first million-
strong cities possibly appearing in late medieval times. By the nineteenth century,
London and Paris had clearly reached this size. Now, there are many cities with
between 10 and 20 million inhabitants. These are continuing to grow, rapidly.
Urbanization is a direct result of a population explosion. Since 1800, global
population has risen from roughly 1 billion, to 6.5 billion in 2000 and a projected 9
billion by 2050. That population growth is linked with the Industrial Revolution,
which supplied the power and technology to feed those extra mouths. Cities,
and especially megacities like Jakarta, Rio de Janeiro or Shanghai, are now the
most visible expression of human influence on the planet. The growth of cities is
therefore a characteristic feature of the Anthropocene.
In ‘terraforming’ cities and building the dams and agricultural land that water
and feed them, humans have wrought a roughly order of magnitude change
in the long-term rate of erosion and sedimentation [9,10]. Paradoxically, while
deforestation and changes in land use have resulted in more sediment transported
in rivers, many of those rivers are now dammed, preventing the flow of that
sediment to continental shelves [11]. Such changes may be impermanent. If
Phil. Trans. R. Soc. A (2011)
on February 2, 2011rsta.royalsocietypublishing.orgDownloaded from

Introduction. Anthropocene epoch 837
human construction were to stop, for instance, nature would soon take over
these constructions, reducing them to ruins over a matter of centuries. After
a few millennia, perhaps only a patchy layer of concrete and building rubble
would remain.
The biological and chemical signals left by humans—invisible, intangible in our
day-to-day lives—may leave a signal more profound than the physical structures
of the world’s megacities. Thus, dissolution of increased atmospheric CO2into the
oceans is increasing their acidity. A significant drop in oceanic pH has already
occurred, and further decreases are almost certain. The biological response is
complex, but will stress many calcifying organisms such as corals or the marine
plankton that form the base of many food chains. Ocean acidification alone may
substantially change marine ecosystems over the next century, contribute to
global biodiversity decline, and so produce a distinctive event in the future
fossil record.
3. Dealing with geological time
The Earth is over 4.5Gyr old. This vast time span encompasses the formation
of our planet and its oceans and continents, the origin of life and the evolution
of the biosphere to its present complexity. To cope practically with such an
extent of geological time, it is divided into more manageable packages that
range from eons encompassing hundreds of millions—or indeed billions—of years,
through smaller packages of time, such as the eras, typically characterized by a
distinctive fossil record, perhaps most notably the dinosaurs and ammonites for
the Mesozoic era beginning about 250 Ma and terminating some 66 Ma. These
in turn are subdivided into periods of geological time, such as the Cambrian
or Cretaceous, that may include distinctive, extensive rock units, such as the
chalk strata of the latter. Periods are divided further into epochs and ages, and
the record of fossils in rocks that were deposited in these shorter intervals of
time is now so well constrained that we can correlate such units globally and
reconstruct the appearance and conditions of our planet for many hundreds of
different time slices.
The last period of time, the Quaternary, began just 2.6 Ma, and includes two
epochs, the Pleistocene and the Holocene. The latter—by far the shortest in the
geological time scale—began only about 11 500 years ago, witnessed by changes
in climate that manifest in an ice core from Greenland [12]. The Holocene is
really just the last of a series of interglacial climate phases that have punctuated
the severe icehouse climate of the past 2 Myr. We distinguish it as an epoch
for practical purposes, in that many of the surface bodies of sediment on which
we live—the soils, river deposits, deltas, coastal plains and so on—were formed
during this time.
4. Examining the Anthropocene
To the Quaternary period a third epoch might be added, the Anthropocene.
Should it be formalized, and join the Carboniferous, the Jurassic, the Pleistocene
and other such units on the geological time scale? This would be a major change
to perhaps the most fundamental framework—the temporal one—used by Earth
Phil. Trans. R. Soc. A (2011)
on February 2, 2011rsta.royalsocietypublishing.orgDownloaded from

838 J. Zalasiewicz et al.
scientists. Such changes are not carried out lightly, and require wide discussion,
consensus and agreement, under the aegis of the International Commission on
Stratigraphy and the International Union of Geological Sciences. Are the changes
involved in the Anthropocene of sufficient scale to warrant such formalization
and—whether they are or not—is it useful to formalize the term in this way?
Formalization would require precision of definition—and that would certainly
help international and interdisciplinary communication. But excessive formality,
of course, can act as a hindrance to working science. Where is the line to be
drawn here?
This Theme Issue is a contribution to this debate, and was conceived
to examine various aspects of the Anthropocene, and to stimulate debate,
both about the term itself and (more importantly) about the phenomenon it
encompasses: the transformation of the Earth’s surface environments by human
activity. This phenomenon is now arguably the most important question of our
age—scientifically, socially and politically. We cannot think of a greater or more
urgent challenge.
The opening paper of this issue by Steffen et al.[13] (the authorship including
the architect of the term ‘Anthropocene’, Paul Crutzen) provides historical
context to the Anthropocene concept, and examines the rapidly evolving—indeed,
accelerating—trends in many global environmental signals, from resource use
on land to patterns of oceanic and atmospheric chemistry. The authors stress
recent human innovations—for instance, the startling advances in genomics that
may profoundly impact on the future evolution of the biosphere. The effects of
such transformational technologies may come to dwarf those of the smokestack
industries, as regards lasting effects on this planet.
The Anthropocene is here treated as a geological phenomenon, comparable
to some of the great events of the Earth’s deep past. But, the driving force
for the component global changes is firmly centred in human behaviour,
particularly in social, political and economic spheres. The paper by Kellie-
Smith & Cox [14] examines the relations between the financial markets and the
Earth’s environmental life support systems. They suggest that the future course
of this relation may be influenced by a stabilizing negative feedback—thus, as
environmental degradation hinders economic development, adverse affects on the
markets will limit investment, acting as a brake on the likes of resource depletion
and carbon emissions.
The science of Anthropocene change to the oceans is analysed by Tyrrell [15].
The major phenomena here are warming (and sea ice loss at high latitudes), sea-
level rise and acidification, all demonstrably processes that are already initiated;
and changes to ocean circulation, that have yet to be clearly demonstrated.
Tyrrell shows how processes such as carbonate compensation will probably
lead to continuing ocean change for many millennia into the future, even after
anthropogenic CO2emissions cease.
Vidas [16] examines the history of the law of the sea, the framework that
regulates humanity’s exploitation of the vast (but finite) resource of the oceans.
This framework stemmed from the early seventeenth century concept of Mare
Liberum—‘the freedom of the seas’—by Hugo Grotius (originally commissioned
to justify what was, in effect, the life of the privateer). Subsequently shaped
by national, territorial forces, this developed into the modern framework, where
geological concepts (like the extent of the continental shelf) remain central to
Phil. Trans. R. Soc. A (2011)
on February 2, 2011rsta.royalsocietypublishing.orgDownloaded from

Introduction. Anthropocene epoch 839
such matters as national claims to stretches of the sea. Now, Vidas argues, as
the oceans themselves change through anthropogenic pressure, one must envision
new principles that acknowledge those pressures, to underpin future iterations of
the law of the sea. Tickell [17] reflects more widely on the societal economic and
social trends that brought about humanity’s current, pivotal situation—and on
the kind of dynamics and institutional arrangements that may be needed to allow
an Anthropocene epoch in which future generations can thrive.
Haywood et al.[18] analyse some of the ancient climates of Earth. They
conclude that the relevance of studying ancient warm climates is not in
the search for a direct analogue for twenty-first century global warming, but
in the assessment and calculation of the response of global temperatures to
increasing CO2concentrations in the longer term (over multiple centuries), and
in the assessment of the abilities of climate and Earth system models to predict
future climate.
Syvitski & Kettner [19] show that the impact of humans on sediment flux began
some 3000 years ago within the Yellow River basin. This trend accelerated in the
past 1000 years, and the sum of human activity through deforestation, agriculture,
mining, transport, waterway ‘re-plumbing’, coastal trawling and climate change
has produced an effect equivalent to the level of a geological climate event, such
as seen in the transition between the Pleistocene and the Holocene.
Merritts et al.[20] show that conceptual models linking channel condition and
sediment yield exclusively with modern upland land use are incomplete for valleys
impacted by mill dams. With no equivalent in the Holocene or Late Pleistocene
sedimentary record, modern incised stream channel forms in the mid-Atlantic
region of the USA represent a transient response to both base-level forcing and
major changes in land use beginning centuries ago.
Ellis [21] considers the transformation of much of the terrestrial biosphere into
anthropogenic biomes, or anthromes. He analyses the scale of this transformation
by comparing the extent of change through different time slices of the Holocene.
While human influence has been significant for more than 8000 years, it is only the
last century that has seen a majority of the biosphere transformed into intensively
used anthromes, and these are characterized by novel ecological processes, in
increasingly profound manipulations of entire ecosystems.
Zalasiewicz et al.[22] consider contemporary environmental trends in
stratigraphic terms, for instance, translating landscape modification (including
urban growth) as a new lithostratigraphic signal, and biodiversity change as the
fossil record of the future. Factoring in the potential for preservation of modern
anthropogenic phenomena means that some of the most striking contemporary
signals, such as megacity growth, may have low preservation potential, depending
on tectonic setting. Conversely, biodiversity changes (including such novel aspects
as unprecedented levels of global species transfer) have considerable permanence
in determining the future course of biotic development.
The stratigraphic signal left by humans is continued by Price et al.[23], who
discuss the gemorphological impact of humans on Earth. They note that in the
past 200 years, humans in the UK alone have excavated and built up more than
four times the volume of Ben Nevis, Britain’s highest mountain. Vane et al.[24]
continue this theme, identifying a range of pollutants preserved in the sediments
of the River Clyde that provide a stratigraphical record of the rise of Glasgow,
one of the world’s first industrial cities.
Phil. Trans. R. Soc. A (2011)
on February 2, 2011rsta.royalsocietypublishing.orgDownloaded from

840 J. Zalasiewicz et al.
It is clear that much work remains to be undertaken to understand the
Anthropocene, even as its defining processes evolve. Considering the present
in terms of the deep past, and vice versa, is difficult, because the methods of
description and analysis of these two temporal realms are often greatly different.
Nevertheless, it is important to try to put contemporary changes to the Earth,
as clearly as possible, into a deep time context. This Theme Issue is intended
as a step in that direction. The results of the studies herein, in sum, indicate
that anthropogenic influence on Earth, albeit only briefly sustained (to date) on
geological time scales, is likely to have significant and long-lasting consequences.
The Anthropocene, on current evidence, seems to show global change consistent
with the suggestion that an epoch-scale boundary has been crossed within the
last two centuries.
References
1 Marsh, G. P. 1864 Man and nature: or, physical geography as modified by human action. New
York, NY: C. Scribner.
2 Stoppani, A. 1871–1873 Corsa di geologia. Milan, Italy: Bernardoni & Brigola.
3 Arrhenius, S. 1896 On the influence of carbonic acid in the air upon the temperature of the
ground. Lond. Edinb. Dublin Phil. Mag. J. Sci. (fifth series) 41, 237–275.
4 Chamberlin, T. C. 1897 A group of hypotheses bearing on climatic changes. J. Geol. 5, 653–683.
(doi:10.1086/607921)
5 Crutzen, P. J. 2002 Geology of mankind. Nature 415, 23. (doi:10.1038/415023a)
6 Zalasiewicz, J. et al. 2008 Are we now living in the Anthropocene? GSA Today 18, 4–8.
(doi:10.1130/GSAT01802A.1)
7 Zalasiewicz, J., Williams, M., Steffen, W. & Crutzen, P. 2010 The new world of the
Anthropocene. Environ. Sci. Technol. 44, 2228–2231. (doi:10.1021/es903118j)
8 Ruddiman, W. F. 2003 The anthropogenic greenhouse era began thousands of years ago. Clim.
Change 61, 261–293. (doi:10.1023/B:CLIM.0000004577.17928.fa)
9 Hooke, R. LeB. 2000 On the history of humans as geomorphic agents. Geology 28, 843–846.
(doi:10.1130/0091-7613(2000)28<843:OTHOHA>2.0.CO;2)
10 Wilkinson, B. H. 2005 Humans as geologic agents: a deep-time perspective. Geology 33, 161–164.
(doi:10.1130/G21108.1)
11 Syvitski, J. P. M., Vörösmarty, C. J., Kettner, A. J. & Green, P. 2005 Impact of humans on
the flux of terrestrial sediment to the global coastal ocean. Science 308, 376–380. (doi:10.1126/
science.1109454)
12 Walker, M. et al. 2009 Formal definition and dating of the GSSP (Global Stratotype Section
and Point) for the base of the Holocene using the Greenland NGRIP ice core, and selected
auxiliary records. J. Quat. Sci. 24, 3–17. (doi:10.1002/jqs.1227)
13 Steffen, W., Grinevald, J., Crutzen, P. & McNeill, J. 2011 The Anthropocene: conceptual and
historical perspectives. Phil. Trans. R. Soc. A 369, 842–867. (doi:10.1098/rsta.2010.0327)
14 Kellie-Smith, O. & Cox, P. M. 2011 Emergent dynamics of the climate–economy system in the
Anthropocene. Phil. Trans. R. Soc. A 369, 868–886. (doi:10.1098/rsta.2010.0305)
15 Tyrrell, T. 2011 Anthropogenic modification of the oceans. Phil. Trans. R. Soc. A 369, 887–908.
(doi:10.1098/rsta.2010.0334)
16 Vidas, D. 2011 The Anthropocene and the international law of the sea. Phil. Trans. R. Soc. A
369, 909–925. (doi:10.1098/rsta.2010.0326)
17 Tickell, C. 2011 Societal responses to the Anthropocene. Phil. Trans. R. Soc. A 369, 926–932.
(doi:10.1098/rsta.2010.0302)
18 Haywood, A. M., Ridgwell, A., Lunt, D. J., Hill, D. J., Pound, M. J., Dowsett, H. J., Dolan,
A. M., Francis, J. E. & Williams, M. 2011 Are there pre-Quaternary geological analogues for a
future greenhouse warming? Phil. Trans. R. Soc. A 369, 933–956. (doi:10.1098/rsta.2010.0317)
Phil. Trans. R. Soc. A (2011)
on February 2, 2011rsta.royalsocietypublishing.orgDownloaded from

Introduction. Anthropocene epoch 841
19 Syvitski, J. P. M. & Kettner, A. 2011 Sediment flux and the Anthropocene. Phil. Trans. R.
Soc. A 369, 957–975. (doi:10.1098/rsta.2010.0329)
20 Merritts, D. et al. 2011 Anthropocene streams and base-level controls from historic dams
in the unglaciated mid-Atlantic region, USA. Phil. Trans. R. Soc. A 369, 976–1009.
(doi:10.1098/rsta.2010.0335)
21 Ellis, E. C. 2011 Anthropogenic transformation of the terrestrial biosphere. Phil. Trans. R. Soc.
A369, 1010–1035. (doi:10.1098/rsta.2010.0331)
22 Zalasiewicz, J. et al. 2011 Stratigraphy of the Anthropocene. Phil Trans. R. Soc. A 369, 1036–
1055. (doi:10.1098/rsta.2010.0315)
23 Price, S. J., Ford, J. R., Cooper, A. H. & Neal, C. 2011 Humans as ma jor geological and
geomorphological agents in the Anthropocene: the significance of artificial ground in Great
Britain. Phil. Trans. R. Soc. A 369, 1056–1084. (doi:10.1098/rsta.2010.0296)
24 Vane, C. H., Chenery, S. R., Harrison, I., Kim, A. W., Moss-Hayes, V. & Jones, D. G. 2011
Chemical signatures of the Anthropocene in the Clyde estuary, UK. Phil. Trans. R. Soc. A 369,
1085–1111. (doi:10.1098/rsta.2010.0298)
Phil. Trans. R. Soc. A (2011)
on February 2, 2011rsta.royalsocietypublishing.orgDownloaded from