[ENWL-uni] *[Enwl-eng] Feature: Debating the Onset of the Anthropocene

[ENWL.Bellona]

17 May 2010: Analysis

The Anthropocene Debate: Marking Humanity's Impact
Is human activity altering the planet on a
scale comparable to major geological events of
the past? Scientists are now considering whether
to officially designate a new geological epoch to
reflect the changes that homo sapiens have
wrought: the Anthropocene.

by elizabeth kolbert

The Holocene - or "wholly recent" epoch - is what
geologists call the 11,000 years or so since the
end of the last ice age. As epochs go, the
Holocene is barely out of diapers; its immediate
predecessor, the Pleistocene, lasted more than
two million years, while many earlier epochs,
like the Eocene, went on for more than 20 million
years. Still, the Holocene may be done for.
People have become such a driving force on the
planet that many geologists argue a new epoch -
informally dubbed the Anthropocene - has begun.

In a recent paper titled "The New World of the
Anthropocene," which appeared in the journal
Environmental Science and Technology, a group of
geologists listed more than a half dozen
human-driven processes that are likely to leave a
lasting mark on the planet - lasting here
understood to mean likely to leave traces that
will last tens of millions of years. These
include: habitat destruction and the introduction
of invasive species, which are causing widespread
extinctions; ocean acidification, which is
changing the chemical makeup of the seas; and
urbanization, which is vastly increasing rates of
sedimentation and erosion.

Human activity, the group wrote, is altering the
planet "on a scale comparable with some of the
major events of the ancient past. Some of these
changes are now seen as permanent, even on a
geological time-scale."

Prompted by the group's paper, the Independent of
London last month conducted a straw poll of the
members of the International Commission on

Are we living in the Anthropocene? The
answer, the group of geologists concluded, was
probably yes.

Stratigraphy, the official keeper of the
geological time scale. Half the commission
members surveyed said they thought the case for a
new epoch was already strong enough to consider a
formal designation.

"Human activities, particularly since the onset
of the industrial revolution, are clearly having
a major impact on the Earth," Barry Richards of
the Geological Survey of Canada told the
newspaper. "We are leaving a clear and unique
record."

The term "Anthropocene" was coined a decade ago
by Paul Crutzen, one of the three chemists who
shared the 1995 Nobel Prize for discovering the
effects of ozone-depleting compounds. In a paper
published in 2000, Crutzen and Eugene Stoermer, a
professor at the University of Michigan, noted
that many forms of human activity now dwarf their
natural counterparts; for instance, more nitrogen
today is fixed synthetically than is fixed by all
the world's plants, on land and in the ocean.
Considering this, the pair wrote in the
newsletter of the International
Geosphere-Biosphere Programme, "it seems to us
more than appropriate to emphasize the central
role of mankind in geology and ecology by
proposing to use the term 'anthropocene' for the
current geological epoch." Two years later,
Crutzen restated the argument in an article in
Nature titled "Geology of Mankind."

The Anthropocene, Crutzen wrote, "could be said
to have started in the latter part of the
eighteenth century, when analyses of air trapped
in polar ice showed the beginning of growing
global concentrations of carbon dioxide and
methane."

Soon, the term soon began popping up in other
scientific publications. "Riverine quality of the
Anthropocene," was the title of a 2002 paper in
the journal Aquatic Sciences.

"Soils and sediments in the anthropocene," read
the title of a 2004 editorial in the Journal of
Soils and Sediments.

Jan Zalasiewicz, a geologist at the Britain's
University of Leicester, found the spread of the
concept intriguing. "I noticed that Paul
Crutzen's term was

One argument against the idea is that humans
have been changing the planet for a long time.

appearing in the serious literature, in papers in
Science and such like, without inverted commas
and without a sense of irony," he recalled in a
recent interview. At the time, Zalasiewicz was
the head of the stratigraphic commission of the
Geological Society of London. At luncheon meeting
of the society, he asked his fellow
stratigraphers what they thought of the idea.

"We simply discussed it," he said. "And to my
surprise, because these are technical geologists,
a majority of us thought that there was something
to this term."

In 2008, Zalasiewicz and 20 other British
geologists published an article in GSA Today, the
magazine of the Geological Society of America,
that asked: "Are we now living in the
Anthropocene?" The answer, the group concluded,
was probably yes: "Sufficient evidence has
emerged of stratigraphically significant change
(both elapsed and imminent) for recognition of
the Anthropocene... as a new geological epoch to
be considered for formalization." (An epoch, in
geological terms, is a relatively short span of
time; a period, like the Cretaceous, can last for
tens of millions of years, and an era, like the
Mesozoic, for hundreds of millions.) The group
pointed to changes in sedimentation rates, in
ocean chemistry, in the climate, and in the
global distribution of plants and animals as
phenomena that would all leave lasting traces.
Increasing carbon dioxide levels in the
atmosphere, the group wrote, are predicted to
lead to "global temperatures not encountered
since the Tertiary," the period that ended 2.6
million years ago.

Zalasiewicz now heads of the Anthropocene Working
Group of the International Commission on
Stratigraphy, which is looking into whether a new
epoch should be officially designated, and if so,
how. Traditionally, the boundaries between
geological time periods have been established on
the basis of changes in the fossil record - by,
for example, the appearance of

"What's going to happen in the 21st century
could be even more significant," a geologist says.

one type of commonly preserved organism or the
disappearance of another. The process of naming
the various periods and their various subsets is
often quite contentious; for years, geologists
have debated whether the Quaternary - the
geological period that includes both the Holocene
and its predecessor, the Pleistocene - ought to
exist, or if the term ought to be abolished, in
which case the Holocene and Pleistocene would
become epochs of the Neogene, which began some 23
million years ago. (Just last year, the
International Commission on Stratigraphy decided
to keep the Quaternary, but to push back its
boundary by almost a million years.)

In recent decades, the ICS has been trying to
standardize the geological time scale by choosing
a rock sequence in a particular place to serve as
a marker. Thus, for example, the marker for the
Calabrian stage of the Pleistocene can be found
at 39.0385°N 17.1348°E, which is in the toe of
the boot of Italy.

Since there is no rock record yet of the
Anthropocene, its boundary would obviously have
to be marked in a different way. The epoch could
be said simply to have begun at a certain date,
say 1800. Or its onset could be correlated to the
first atomic tests, in the 1940s, which left
behind a permanent record in the form of
radioactive isotopes.

One argument against the idea that a new
human-dominated epoch has recently begun is that
humans have been changing the planet for a long
time already, indeed practically since the start
of the Holocene. People have been farming for
8,000 or 9,000 years, and some scientists - most
notably William Ruddiman, of the University of
Virginia - have proposed that this development
already represents an impact on a geological
scale. Alternatively, it could be argued that the
Anthropocene has not yet arrived because human
impacts on the planet are destined to be even
greater 50 or a hundred years from now.

ABOUT THE AUTHOR
Elizabeth Kolbert, who conducted this interview
for Yale Environment 360, has been a staff writer
for the New Yorker since 1999. Her 2005 New
Yorker series on global warming, "The Climate of
Man," won a National Magazine Award and was
extended into a book, Field Notes from a
Catastrophe, which was published in 2006. Prior
to joining the staff of the New Yorker, she was a
political reporter for the New York Times. In her
most recent article for Yale Environment 360, she
reported on a new study that found the pace of
global warming is outstripping the most recent
projections of the Intergovernmental Panel on
Climate Change.



http://e360.yale.edu/content/feature.msp?id=2274

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Sent: Thursday, May 20, 2010 8:57 PM
Subject: Feature: Debating the Onset of the Anthropocene

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