THERE is no doubt that human beings are the dominant species on Earth. The seven billion of us account for about one-third of the total body mass of large animals on the planet, with our domestic animals accounting for most of the rest. (Wild animals only amount to 3 to 5 percent.) But are we really central to the scheme of things? That is a different question.

Almost all the scientific discoveries of the past few centuries have moved human beings away from the centre of things towards the periphery. In the 16th century we learned that Earth went around the Sun, not the other way round.

Then we realised that the Sun was just one more yellow star among a hundred billion others “far out in the uncharted backwaters of the unfashionable end of the western spiral arm of the Galaxy,” as Douglas Adams put it. And this is just one galaxy among hundreds of billions.

Then the geologists learned that our planet is four and a half billion years old, whereas we primates have only been around for the past seven million years, and modern human being for a mere 100,000 years. And so on and so forth, until we felt very small and insignificant. But now the story is heading back in the other direction; they’re going to name an entire geological epoch after us. The Anthropocene.

Don’t get too excited: an epoch is not that big a deal in geology. Just as there is an ascending hierarchy of days, weeks, months and years in present time, there is a hierarchy of epochs, periods, eras and aeons in geological time. Until recently, everybody agreed that we live in the Holocene epoch of the Quaternary period, which in turn is part of the 65-million-year old Cenozoic era, the most recent phase of the 540-million-year Phanerozoic aeon.

Holocene means “entirely recent”, and is reckoned to have begun at the end of the last major glaciation less than 12,000 years ago. That’s not a very long time even for a mere epoch – but geologists are now considering the possibility that we have already entered a different epoch, the Anthropocene (from the Greek roots for “man” and “recent”). That is, an epoch defined by the impact of human beings on the entire planetary environment.

Geologists want to see evidence in the rocks before they define an epoch, and it’s early days for that yet, but it’s clear that the fossil records for the present time will show a massive loss of forests, a very high rate of extinctions, and a preponderance of fossils of only a few species: us and our domesticated animals.

The acidification of the oceans is destroying the coral reefs, which will produce a “reef gap” similar to the ones that marked the five great extinctions of the past. The changes in the atmosphere caused by the burning of massive amounts of fossil fuels – coal, oil and gas – will show up in the form of rising sea levels due to warming, and in the decline of carbonate rocks like limestone and chalk in the deep-ocean sediments.

If this is really a new epoch, then geologists (human or otherwise) millions of years from now should be able to work out what happened just from the rocks, without any direct knowledge of the past. However, if the current global civilisation collapses as a result of these changes, they will have only a very thin band of rock to work with.

The idea of declaring the Anthropocene as a new epoch is being taken seriously by geologists: the International Union of Geological Sciences has set up a working group of the International Commission on Stratigraphy to report by 2016 on whether the Holocene must give way to the Anthropocene.

They will also have to decide when the Anthropocene began. In 1950, at the start of the “Great Acceleration” that saw the human population and its greenhouse gas emissions both triple in only six decades? At the start of the Industrial Revolution two-and-a-half centuries ago? Or eight thousand years ago, when the first farmers began to clear forests and emit significant amounts of greenhouse gases? Take your pick, because it doesn’t matter.

The real purpose of declaring the Anthropocene period is to focus human attention on the scale of our impacts on the planetary environment. As biologist E.O. Wilson wrote: “The pattern of human population growth in the twentieth century was more bacterial than primate.” He calculated that human biomass is already a hundred times larger than that of any other large animal species present or past except for our own domesticated animals.

That phase of runaway population growth is over now, but the global rise in living standards is having further environmental impacts of the same order. Climate change is the headline threat, but the loss of biodiversity, ozone depletion, ocean acidification and half a dozen other negative trends are also driven by our numbers and our lifestyle.

Being responsible for keeping so many interlocking systems within their permissible limits may be more than our civilisation can manage, but it’s already too late to reject that job. All we can do now is try to stay within the planetary boundaries (which in some cases requires discovering exactly where they are), and restore as many natural systems as we can. The odds are not in our favour.

(By Gwynne Dyer)