Australasian Science: Australia's authority on science since 1938

Welcome to the Anthropocene

Credit: Mopic

Credit: Mopic

By Will Steffen

Say goodbye to the Holocene. Later this year a new epoch might be formally recognised.

The Palaeocene, the Oligocene, the Eocene, the Pliocene, the Pleistocene and, most recently, the Holocene are time periods marking significant changes in the evolution of the planet, all the way from its beginning about 4.6 billion years ago to the present. Often these periods mark changes in the biosphere, such as the evolution of multicellular organisms or the extinction of the dinosaurs, or changes in the climate, such as the swings between “icehouse” and “hothouse” conditions.

These changes have been driven by the internal dynamics of the Earth itself, such as plate tectonics and the evolution of life, but also by extraterrestrial factors such as large meteorite strikes or changes in the orbit of the Earth around the Sun. This brings us to the idea that a new epoch has commenced.

The Anthropocene is different because it is being driven by the myriad activities of our increasingly globalised human society. This means that the concept of the Anthropocene is immediately beyond the expertise of natural scientists alone, attracting increasing attention from social scientists and humanities scholars as well as the public at large.

There is nevertheless a strong natural science basis to the Anthropocene, drawing primarily from two broad areas of the sciences – stratigraphy and Earth System science.

Stratigraphers are the timekeepers of planet Earth, so theirs is a very old art. Using a wide variety of tools to interpret the rock strata of the planet, going back to nearly 4 billion years ago, they have devised careful rules to determine whether or not a new time period can be determined. Two of the most important of these rules are that:

  • the rock strata above a proposed boundary are distinctly different from those below; and
  • the distinction is globally synchronous, indicating that the change is global and not merely regional in character.

The Anthropocene is challenging because it is emerging as it is being studied rather than being a sharp distinction in the rock strata of the distant past. Nevertheless, stratigraphers have made remarkable progress in identifying markers characteristic of the Anthropocene in today’s emerging strata. These include plastics, concrete, aluminium, radionuclides and spheroidal carbon particles originating from the burning of fossil fuels. All of these markers are undeniably of human origin and are widespread around the planet.

All of these stratigraphic markers begin to appear in significant amounts around the middle of the 20th century, and they are globally synchronous, appearing everywhere around the planet at approximately the same time. “Significant amounts” might be an understatement; the amounts of these new materials released into the planetary environment are staggering.

The total amount of concrete that humanity has produced, most of it in the post-1950 period, amounts to about 1 kg /m2 across the entire surface of the Earth. The amount of plastic wrap produced since 1950 is enough to cover the entire planet in plastic. Enough aluminium foil has been manufactured to wrap the continent of Australia.

Humans and our domesticated animals, such as cattle, sheep, pigs and chickens, now account for more than 95% of the mass of all vertebrate animals on land, while wild animals account for only 3%. Humans alone account for ten times the mass of all of the wild animals on all continents put together.

The developing deposits resulting from the extraordinary amount of new material produced by humans meet the stratigraphic criteria for a new time period in the Earth’s history. Based on these data, a case for formalising the Anthropocene will be put to the International Commission on Stratigraphy later this year at its conference in South Africa. At present, the Anthropocene, although very widely used, remains an informal term.

The current proposal for a new geological epoch called the Anthropocene arose from the Earth System research community, which has independently been accumulating evidence for the emergence of the Anthropocene for about 15 years. According to the Earth System approach, the Earth is a single complex system that exists in well-defined states with transitions between them.

The most recent geological epoch – the Holocene – is a well-defined state of the Earth System that has followed on from the most recent ice age. The Anthropocene represents a destabilisation of the Holocene state – accelerating change in the climate, rapid loss of biodiversity, massive disruption of nitrogen and phosphorus cycles that is polluting lakes, rivers and the coastal zone, the creation of an ozone hole over Antarctica, and so on.

Put simply, Earth System scientists have amassed an enormous amount data showing that human activities are driving the global environment out of its stable Holocene state.

Not surprisingly, the Earth System data have also shown a dramatic increase in our impact on Earth System functioning since the mid-20th century, a phenomenon that has been dubbed the “Great Acceleration”. This is where the social scientists and humanities scholars come in.

Although it’s tempting to suggest that the Anthropocene started with the beginning of the Industrial Revolution, other changes were at least as important as the technology of the Industrial Revolution itself. These analyses emphasise the importance of two world wars and a great depression in breaking down old feudal institutions, building new institutions based on neo-liberal economic principles, the post-World War II rise of science and technology, and the acceleration of globalisation from the mid-20th century. This sharp discontinuity in socio-economics ultimately triggered the Great Acceleration and ushered in the Anthropocene.

There are other significant socio-economic implications of the Anthropocene. Although natural scientists often lump all humans around the planet into one “humanity-as-a-whole”, this generalisation masks important inequities within and between countries. Focusing on these inequalities, some humanities scholars have asked: “Which humanity is responsible for the Anthropocene?”

The answer to that question is startling. Ultimately, the changes to the global environment that mark the Anthropocene are driven by pressures arising from human consumption of goods and services and the technologies that produce them – the engine room of the post-World War II economy. Splitting “humanity” into only three groups – the wealthy OECD countries, the rapidly emerging countries of China, India, Brazil, Russia and South Africa (BRICS), and the rest, mainly poor, countries unmasks some fascinating trends.

Population growth since the mid-20th century has been dominated by the BRICS and the poor countries (primarily the latter), while the global economy remains dominated by the OECD countries despite the recent economic rise of China. In 2010 the OECD nations accounted for only 18% of the global population but generated 74% of the world’s GDP, and with it accounted for the vast majority of the consumption that is the primary driver of the Anthropocene.

The Anthropocene is only beginning, and its final length and significance isn’t known. So the advent of the Anthropocene raises the ultimate question: where on Earth are we going?

Will Steffen is Emeritus Professor at The Australian National University, and Councillor of the Climate Council of Australia.