n February 2000, a conference of the International Geosphere-Biosphere Programme held in Cuernavaca, Mexico, hosted a heated discussion about the age and intensity of human impacts on the planet. Paul Crutzen, an atmospheric chemist and Nobel Prize winner for his work on the ozone layer, stood up and exclaimed: ‘No! We’re no longer in the Holocene but in the Anthropocene!’ This was the birth of a new word, and above all of a new geological epoch. Two years later, in an article in the scientific periodical Nature
, Crutzen developed his assertion further: the stratigraphic scale had to be supplemented by a new age, to signal that mankind had become a force of telluric amplitude. After the Pleistocene, which opened the Quaternary 2.5 million years back, and the Holocene, which began 11,500 years ago, ‘It seems appropriate to assign the term “Anthropocene” to the present, in many ways human-dominated, geological epoch.’1
The Nobel laureate proposed a starting date for this new era of 1784, the year that James Watt patented the steam engine, symbolic of the start of the industrial revolution and the ‘carbonification’ of our atmosphere by the burning of coal extracted from the lithosphere.
From the ancient Greek words anthropos
meaning ‘human being’ and kainos
meaning ‘recent, new’, the Anthropocene is then
the new epoch of humans. The Anthropocene is characterized by the fact that ‘the human imprint on the global environment has now become so large and active that it rivals some of the great forces of Nature in its impact on the functioning of the Earth system’.2
This is not the first time scientists have attested to or foreseen such human power over the fate of the planet, whether to celebrate it or as a cause for concern. As recently as 1778, in his Epochs of Nature
volume of Histoire naturelle générale et particulière
, Buffon explained that ‘the entire face of the Earth today bears the imprint of human power’. This imprint would be particularly exerted on climate. By judiciously modifying its environment, humanity would be able to ‘modify the influences of the climate it inhabits, and set the temperature to the level that suits it best’.3
Following him, the Italian geologist Antonio Stoppani defined humankind in 1873 as a ‘new telluric power’, and in the 1920s Vladimir I. Vernadsky, who introduced the concept of the biosphere, emphasized the growing human effect on the globe’s biogeochemical cycles.4
Nor was this the first time that scientists succumbed to anthropocentrism in making humanity a geological marker: the start of the Quaternary, in fact, was fixed to coincide with the appearance of the genus Homo
2.5 million years ago in Africa (Homo habilis
), and the Holocene or ‘recent epoch’ was proposed by the geologist Charles Lyell on the basis of the end of the last glaciation but also on the then-believed coincident emergence of humans. The idea of adding the Holocene to the geologic time clock was put forward by Charles Lyell in 1833, but accepted only in 1885. Geologists, accustomed to working on the scale of the Earth’s 4.5-billion-year history, have no reason to hurry in making our entry into the Anthropocene official. Besides, if the history of our planet is reduced to a day of
twenty-four hours, Homo habilis
appeared only in the final minute, the Holocene began in the last quarter of a second, and the industrial revolution only in the two last thousandths of a second. With the Pleistocene counting in millions of years, and the Holocene in thousands, Crutzen’s boldness in proclaiming a new Anthropocene dating back no more than a couple of centuries is readily understandable. His proposal will very likely continue to be debated for a while to come. At the 34th
congress of the International Union of Geological Sciences, held in Brisbane in 2012, it was decided to establish a task group that would submit its report in 2016.
While awaiting official validation by stratigraphers, however, the Anthropocene concept has already become a rallying point for geologists, ecologists, climate and Earth system specialists, historians, philosophers, social scientists, ordinary citizens and ecological movements, as a way of conceiving this age in which humanity has become a major geological force.
What humans are doing to the Earth
hat are the arguments put forward? What imprints do humans make on the planet, albeit in a differentiated way that we shall explore below? For atmospheric chemists such as Paul Crutzen, or climatologists such as the Australian Will Steffen and the Frenchman Claude Lorius, the weapon that put an end to the Holocene is to be found in the air: ‘The air trapped in ice is an abrupt indication that the hand of man, by inventing the steam engine, upset the world machine at the same time.’5
Fingers point to the greenhouse gases emitted by human activity. In relation to 1750, as a result of these emissions, the atmosphere has been ‘enriched’ in methane (CH4
) to the tune of 150 per cent, nitrous oxide (N2
O) by 63 per cent and carbon dioxide (CO2
) by 43 per cent. As far as the last of these is concerned, its concentration has risen from 280 parts per million (ppm) on the eve of the industrial
revolution to 400 ppm in 2013, a level unmatched for 3 million years. New ingredients have also entered the atmosphere since 1945: fluoride gases such as the CFCs and HCFCs particularly emitted by our refrigerators and air conditioners.
All these are ‘greenhouse’ gases inasmuch as they retain the heat that the Earth, warmed by the Sun, emits into space. And the accumulation of these gases in the atmosphere has not taken long to raise the planet’s temperature. Since the mid nineteenth century, the thermometer has already risen by 0.8°C, and the scenarios of the UN Intergovernmental Panel on Climate Change (IPCC) foresee, depending on the political response they find, a total rise by the end of the present century of between 1.2°C and 6°C. A rise of 2°C in relation to the pre-industrial level, considered by the majority of climatologists as a danger threshold, will be very hard not to breach given the current lack of international political will, and, if the present tendency is not radically modified, climate experts predict a rise of 3.7°C to 4.5°C by 2100, with a whole train of meteorological disturbances and human miseries in its wake. The IPCC’s latest report even envisions a rise of 8°C to 12°C by 2300, given a ‘business as usual’ scenario. The Andean ice cover in Peru has disappeared in twenty-five years, and the polar ice has been melting in the last few years much faster than experts had expected. While the climatologists of the 1980s and ’90s conceived the relationship between concentration of greenhouse gases and climate change in a more or less global and linear fashion, systemic approaches and recent advances in modelling show that a small variation in the globe’s average temperature can lead to sudden and disorderly changes.
The generalized degradation of Earth’s living tissue (the biosphere) is the second element attesting to our swing into the Anthropocene. The collapse of biodiversity is bound up with the general movement of simplification (by anthropization through agriculture and urbanization), fragmentation and destruction of the globe’s ecosystems, but it is also accelerated by climate change. An article published in Nature
in June 2012 indicates that, even in an optimistic scenario, by the end of the twenty-first century, climate conditions on between 12 and 39 per cent of the Earth’s surface will be such as present living organisms
have never before faced.6
On top of those extinctions directly caused by climate change, there is the damage to sea life caused by the acidification of the oceans (up 26 per cent in relation to the pre-industrial period), since these absorb a quarter of our CO2
In the last few decades, the rate of extinction of species has been from 100 to 1,000 times greater than the geological norm: biologists speak of a ‘sixth extinction’ since the appearance of life on Earth.8
Since the Convention on Biological Diversity of 1992, the pace of extinction has in no way slowed down, for lack of action on the main forces of degradation, and it is estimated that the 100,000 currently protected areas in the world will save at best 5 per cent of all species. Three-quarters of the world’s fishing zones are at maximum production or over-exploited. The mass of humans (32 per cent), along with that of their domestic animals (65 per cent), now makes up 97 per cent of the total biomass of land vertebrates, leaving only 3 per cent for the remaining 30,000 land-dwelling vertebrate species.9
At the current rate, 20 per cent of the planet’s species will have disappeared by 2030,10
but many essential ‘services’ provided to humanity by the biosphere – pollination, carbon capture, protection from erosion, regulation of water quality and quantity, etc. – have already been greatly reduced.
As well as climate change and the collapse of biodiversity, scientists also note other major transformations that attest to our entry into the Anthropocene. These include in particular the biogeochemical cycles of water, nitrogen and phosphate, each as important as that of carbon, which have also come under human control in the course of the last
two centuries. The modification of the continental water cycle is massive, with the draining of half the planet’s wetlands and the construction of 45,000 dams with heights of more than fifteen metres, together retaining 6,500 cubic kilometres of water, some 15 per cent of the total flow of the world’s rivers.11
These transformations have substantially modified the processes of erosion and sedimentation, without however freeing the greater part of humanity from water insecurity.
The nitrogen cycle has been radically transformed with industrialization (the burning of fossil fuel releasing nitrous oxides) and the Haber-Bosch process (1913) that converts atmospheric nitrogen into nitrogen suitable for fertilizer. These two phenomena represent nitrogen flows twice as great as the ‘natural’ flow through the biosphere, basically bound up with biological fixing by bacterial symbiosis.12
The nitric oxide released by fertilizers accentuates the greenhouse effect, and excess urea and nitrates enter water-tables, rivers and estuaries, causing eutrophication and hypoxia.
The global phosphorous cycle also bears the mark of human domination, with an anthropic flow eight times greater than the natural one. Some 20 million tonnes of phosphorous are extracted each year from phosphate mines in the lithosphere, chiefly to be used for fertilizer. It is estimated that 9 million of these 20 million tonnes end up in the oceans.13
Scientists have shown that an increase in phosphate level of only 20 per cent in relation to the underlying natural flow was in the geological past one of the causes for the collapse of the oxygen level in the oceans, leading to the massive extinction of aquatic life.
Scientists and geographers have also attempted to estimate the extent to which terrestrial ecosystems have been turned into the
artificial ones of pasture, crop-land and cities. It turns out that the human species, having increased from a population of 900 million in 1800 to 7 billion in 2012, takes nearly a third of the production of continental biomass for its own needs (in terms of food, clothing, housing and many less vital things),14
and consumes each year one and a half times what the planet can annually produce on a sustainable basis. This means that ‘we’ – meaning above all the 500 million most well-off inhabitants of the globe – are not only consuming the fruits of the tree on which we sit but also sawing through its branches.15
The Anthropocene is characterized by an unprecedented upsurge in energy mobilizat...