The impact of our species on the conditions and fundamental processes on Earth is unmistakable. From carbon emissions to the cities that dominate skylines to the plastics that swirl around in our seas, the evidence of our existence can be found anywhere. And now, a group of geologists considers our impact so drastic that a new epoch – the Anthropocene – should be declared. Whilst this change has gained support in much of the scientific community, others say that the Anthropocene is more about sensationalism or pop culture than science, as clear evidence for a new geological time is lacking. So whilst much of the scientific community, the general public and the media have already embraced the Anthropocene, the search for hard evidence for the start of a human-dominated age continues.

The Search for the Golden Spike

You may not notice it on a daily basis, but you have been officially living in the Meghalayan age of the Holocene epoch your entire life. Starting at the end of the last ice age, roughly 11,700 years ago, and lasting until present day, the Holocene is characterized by a remarkably stable climate (well, until recently) on a global scale and encompasses everything that is human: the development of civilisation, the advent of religion, and the advancement of technology. However, geologists and other scientists say that we are currently living in a period in which humans have such a severe and decisive influence on the current and future state of our planet that a name change is required. Following suggestions to consider the Anthropocene as a formal epoch, the International Commission on Stratigraphy (ICS) – the committee behind the naming of geologic time scales – established the Anthropocene Working Group (AWG) in 2009 to investigate whether the Anthropocene deserves a place on the geologic time scale.

The evidence of human impact on the planet is overwhelming: the dazzling acceleration of carbon dioxide emissions, the extensive transformation of land associated with urbanization and agriculture, and the mass loss of habitat and species – just to name a few. Many of these changes will persist for thousands of years and alter Earth’s dynamics, some permanently. For these changes to highlight the lower boundary of a new geologic stage – the formal criterium to define a new stage – they need to be reflected in stratigraphic material (e.g., rock, glacier ice or marine sediment) using a GSSP (Global Boundary Stratotype Section and Point), also known as a ‘golden spike’. Generally, geologists use changes in multiple geologic records to delimit major changes in Earth’s physical, chemical and biological processes, and thereby geologic stages, such as the appearance of new species as fossils.

To date, the AWG has preliminarily identified the onset of the Anthropocene and possible stratigraphic markers. They suggest that the clearest and most widespread marker are radionuclides spread worldwide by the first nuclear tests, which would place the beginning of the Anthropocene in the 1950s. Other possible markers are the nitrogen and phosphate traces of artificial fertilizers, plastic pollution and the change in carbon isotopes resulting from carbon emissions.

One of the proposed markers for the start of the Anthropocene is the appearance of radionuclides in the atmosphere (Image Credit: National Oceanic and Atmosphere Association, United States Department of Energy, CC0)

The crucial next step is finding stratigraphic evidence for the primary stratigraphic marker that can be correlated with secondary markers around the globe. The AWG has several candidate locations to find the golden spike, including sediment from a lake in southern Ontario, Canada, an ice core from Antarctica and corals in the Great Barrier Reef. They hope to include a single location in their formal proposal, which is planned to be presented to the ICS by 2021. The approval process that follows is complex and time-consuming, as it needs to pass several organisation levels, including the ICS and its parent organisation, the International Union of Geological Sciences, so it may take years before the Anthropocene is formalized.

Acknowledging our Impact

As with any formalisation that marks a direct link between humans and a global-scale impact, there is controversy around the Anthropocene. Some geologists advocate for keeping the use of the term informal but still acknowledge humanity’s impact on our planet. Others are in favour of formalizing the Anthropocene but disagree about when humans began to leave their mark, and thus when the Anthropocene should start, and how (or whether) that is different from the Holocene. Part of the controversy is related to the Holocene. Over the last 2.8 million years, Earth’s climate has been characterized by a cycle of glacials (colder periods, glacier advances) and interglacials (warmer periods, glacier retreat). A total of 49 interglacials passed, but only the current one, the Holocene, was granted the subdivision ‘epoch’, merely because it is the one we live in.

Controversies aside, formalising when humans became a substantial influence on Earth is not only scientific, it’s also politically and socially powerful. Not to mention crucial in a time of human-caused climate and environmental change. Names have power and it may have far-reaching social, economic and political implications whether we live in Meghalayan age of the Holocene, without mentioning our impact on the environment, or in the Anthropocene, emphasising the significance of our actions. Perhaps formally embracing the Anthropocene might be the final push needed for global recognition that we should put our heads together to change the world for the better.

Title Image Credit: Pxhere, CC0 1.0