Sunday, January 1, 2012

The Anthropocene: when we humans create geological eras

The year 2011 is over and the year 2012 starts, but the new year could start the day after tomorrow or in three months because, although a year stands for a revolution of our planet around the Sun, the start of the year is taken at random. Or we could use the Islamic calendar and then it would be the year 1433, or the Nepalese calendar and then it would be the year 2068, or any other calendar currently in use. Or it could be the year 3517 if we were using the Roman calendar or the year 256 if we counted from Wolfgang Amadeus Mozart’s birth date –my personal choice. However, it is true that years, regardless of the starting date, are an interesting measurement tool in this endless ocean of time. In order to measure longer periods of time --for instance, the time since the invention of writing--, historians coined the terms Middle Age, Renaissance, Ancient times or Modern times. For times before the evolution of our species, we use such terms as Neolithic or Palaeolithic. But when applying to the history of our planet and our universe, these periods of time are too short and useless. When we want to talk about really long time lapses, we use eons, eras and periods. The Cambrian (from 542 to 488 million years ago) is a period that marked a profound change in life on Earth, the so-called Cambrian explosion: multicellular organisms first appeared. The Permian (251 million years ago) ended with the largest mass extinction in Earth’s history. During the Triassic, Jurassic and Cretaceous (from 250 to 65 million years ago) dinosaurs ruled our planet.
At present, and following these geologic terms, we are living in the Holocene, which started 11,000 years ago, following the last glacial period. During this epoch, humans discovered agriculture and many more things we have done ever since. But not everybody agrees: some years ago Paul Crutzen, awarded with the Nobel Prize in Chemistry, proposed a controversial idea, which is getting lots of supporters. Since the industrial revolution, the Holocene is over and we are living in the Anthropocene, the age of humans. And this has nothing to do with considering humans the centre of the universe. This term was coined to mark the evidence that human activities have had such a global impact on Earth as to affect the rest of living species and the ecosystems.
Figures speak for themselves: just take a look at these charts to understand why this recently-coined term has so many supporters. In just a few years, the impact of human activities on Earth rocketed: population, amount of domesticated land, atmospheric CO2, methane and N2O concentrations, fertilizer consumption, great floods, water use, deforestation, river and lake pollution, consumption of wood, minerals and fossil fuels, and the extinction of species… all these parameters shoot up. These changes are so profound that life on Earth will be affected for thousands of years, even if we are clever enough to stop it and avoid a catastrophe.
Either we do something about it or some intelligent species who will study our planet in the future will define the Anthropocene as the era of the sixth mass extinction, as if we were revisiting the Permian.


  1. List of currently-used calendars:
  2. About the Nobel Prize-winning Paul Crutzen, known for his research on ozone depletion:
  3. Globaïa, a very interesting web site with data about the Anthropocene:
  4. Charts showing the sudden impact of human activities on Earth:
  5. Mass extinctions:


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