Anthropocene: The human imprint on Earth

It is estimated that 4,570 million years have passed since the formation of planet Earth, and during this huge period, the transformation of our world has been impressive. Little or nothing has to do with the natural conditions of those first few thousand years, compared to what we know today. However, even imperceptibly, the Earth is still changing and adapting to the external and internal agents that reside in its system.

1. The illumination of the Earth shows the human footprint on the planet

That is why the International Commission of Stratigraphy uses a geological time scale, permanently revised, in which it is possible to keep track of all the events that have modified our planet, as if it were a biography. And in the last chapter of that biography, which continues to be written, we appear as a human species, becoming active agents capable of transforming the planet, as recognized since 2000, when Nobel Prize chemistry, Paul Crutzen, Popularized the term Anthropocene.

This word was previously coined by the ecologist researcher Eugene F. Stoermer, and is justified by the fact that during the Holocene human activities have gradually grown into a significant geological and morphological force.

Why a new geologic epoch?

According to statements made by experts in different areas, the expansion of the human being has its own footprint in our world, and this record is expected to last for thousands of years. These are some examples:

• Over the past 3 centuries, the human population has increased tenfold to 6 billion, resulting in an increase in livestock (1.4 billion cattle) and urbanized areas.
• In a few generations, we will exhaust the fossil fuels that took hundreds of millions of years to produce.
• The nitrogen cycle is decompensated. The nitrogen that reaches the atmosphere from fossil fuels and the combustion of biomass is greater than nature can assimilate.
• Around 30-50% of the continental land surface has been transformed by human action.
• More than half of the available water is used by humans.
• Anthropic activities have multiplied by 1,000 the rate of extinction of species in the rain-forest.
• Greenhouse gases have increased substantially in the atmosphere: CO² more than 30%, and CH4 (methane) even beyond 100%. In addition, CFCs (chlorofluorocarbons) could have destroyed the Ozone Layer if no international control measures had been taken.
• Fishing activity eliminates more than 25% of ocean production in the upwelling regions and 35% on the continental shelves.
• The biogeochemical cycle of the water has been modified and can be verified in the lacustrine sediments.

2. Evolution of the temperature since the human being exists. Source: IGBP

Considering the magnitude of all these processes and their durability over the next few thousand years, Crutzen and Stoermer proposed to use the term “Anthropocene” to talk about the present geological age. In particular, they establish the last third of the 18th century as the beginning of the epoch, but do not rule out other valuations, among which the Holocene (the last and present epoch of the Quaternary period) could be included. However, they maintain that, over the last two centuries, the overall effects of human activities are evident.

The Anthropocene and historical geology

It is clear that the effects of the human being on the Earth are visible and the different studies assure that its repercussion has modified the biosphere, the geosphere and the atmosphere. However, one of the most uncertain pitfalls to make the Anthropocene official is the National Stratigraphy Commission’s assessment, because strictly speaking, a geological epoch often reflects significant changes in biota (a set of plant, animal, and other organisms) of each period, and has an estimated duration of 13 to 35 million years. The question is: would this new era last long enough to be considered as such?

In this sense, it is practically impossible to estimate whether the effects of the Anthropocene would prevail for a minimum of 13 million years, because until now the geological epochs have been dated a posteriori by fossil and sedimentary records.
The key, it seems, is the appearance of a stratigraphic layer that contains records of the influence of man, just as we can determine other times through their fossils, such as trilobite or dinosaurs, for example (this characteristic mark is called Golden Spike in geology).

3. Geological scale during the Cenozoic. Source: USGS.gov

Another question that should be asked is: where do we establish the beginning of the Anthropocene? We already know the proposal of Crutzen and Stoermer, who mark the Industrial Revolution as the starting point, as shown by the increase in the concentration of greenhouse gases in the records obtained from the ice sheets (mainly CO² and CH⁴ ). Furthermore, said date coincides with the invention of the steam engine.

But there are other points of view. For example, there has been talk of the beginning of agriculture, about 9,000 years ago, as a possible beginning of the Anthropocene, although it is true that this proposal does not have much support, since it is a gradual phenomenon.

The most widely accepted date appears to be in the mid-twentieth century, with the end of World War II and the detonation of the Hiroshima and Nagasaki bombs, along with the Pacific nuclear tests. After these events, it is now possible to find radioactive elements scattered throughout the planet, through atmospheric and oceanic circulation. In addition, since these years, the industrial and technological acceleration have exerted an increasing pressure on the planet, fruit of capitalism and globalization. Thus, these residues will be registered in the terrestrial layers with the passage of years.

The legacy we leave for History

Undoubtedly, we will leave a mark on planet Earth. And if we were to disappear as a species of its face tomorrow, another intelligent species would be able to reconstruct the geological history just as we did, and see the stratigraphic mark we created: our Golden Spike.

This fossil record would be identifiable by harbouring radioactive particles released after accidents, bombs and nuclear tests, but CO² traces and CFC gases, and most likely bony remains of poultry, would also be found as a result of the growing expansion of poultry farms in many places of the world.

In turn, it would be formed by residues such as concrete, ash, aluminum or plastic, elements very widespread from the second half of the twentieth century, when the capacity of human transformation allowed to modify the natural elements practically without limits.

4. Plastiglomerate. Source: Continente Basura

In fact, a new rock is already known as a product of the waste of human activities: the plastiglomerate. Far from being a joke, the truth is that the amount of plastic we throw to nature is worrisome, especially because of its extremely slow degradation. Plastiglomerates have now been found in the Hawaiian Islands as a result of the melting of plastic, which acts as a “paste” that adheres to other rocky, biological, and even other solid wastes.

The Anthropocene, although it ends up being named in this way, will be evident in the geological strata and will leave no doubt about the human presence in history. It is quite likely that those who find this fossil evidence within a few thousand years will come to really critical conclusions about our behavior as an “intelligent” species. The human race could be analyzed as a plague, a planetary disease that consumes the resources of its host, fatally leading to the death of both. That is the future that awaits us if nothing changes.

* In this link you can find more detailed information about the Anthropocene.