Anthropocene: Really? At what point did humans´ impact on earth become geologically significant?

Geologists are in a hot debate about whether to call for the end of the Holocene Epoch of the the Quaternary Period of the Cenozoic Era of the Phanerozoic Eon.  At issue is whether to declare the beginning of the Anthropocene Epoch -i.e. the Epoch of human caused change to the earth.

On the one hand:

«Stanley C. Finney, the secretary general of the International Union of Geological Sciences, fears the Anthropocene has become a way for geologists to make a “political statement.”»

Our current geologic epoch, the Holocene Epoch began 11,700 years ago with the end of the last big ice age.  The Anthropocene Working Group  (AWG) is the panel that has been deliberating since 2009 on the question of whether the scientific evidence is robust enough for the Anthropocene to be formally ratified by the International Union of Geological Sciences (IUGS) as an Epoch within the Geologic time scale.

“In May, 2019, the AWG completed a binding vote determining two major research questions:

1. "Should the Anthropocene be treated as a formal chrono-stratigraphic unit defined by a GSSP?" (the precise geological stratum-Global Stratotype Section and Point – GSSP).
2. "Should the primary guide for the base of the Anthropocene be one of the stratigraphic signals around the mid-twentieth century of the Common Era?"

Both questions received a positive response within the working group with 29 votes in favor, 4 votes against...”

However, in order for the Anthropocene to be established, the proposal must be ratified by 60% of the three other working groups of the «Subcommission on Quaternary Stratigraphy».

That solution would also avoid the issue of naming the geological stratum, i.e. the Global Stratotype Section and Point (GSSP) to mark the beginning of the Anthropocene.

But various other “milestones”, so to speak, might be the geological basis for the naming of a new era, e.g. 1945 by the appearance of radioactivity, though the first nuclear weapon detonation created no discernible stratigraphic location. 

This tidbit is new and interesting to me: Others put the start of the Anthropocene at A.D. 1610 when the New and Old World fauna were introduced to each other, as well as the drop in atmospheric CO2  (as measured in Antarctic ice cores) that is attributed to farming and «vegetation regrowth on abandoned farmlands following  the deaths of 50 million indigenous Americans (mostly from Smallpox brought by Europeans). In addition to the obvious historical importance, there is a school of thought ("school of thought" may be hyperbole - Its main devotee was Sir Patrick Moore who was known for his eccentricities as well as his extreme conservative views regarding immigration, women,  the BBC , etc. "I may be accused of being a dinosaur, but I would remind you that dinosaurs ruled the Earth for a very long time. — Moore responds to those who criticise his right-wing beliefs)  that suggests that zero CO2 emissions might reduce atmospheric CO2 below the level required for plant growth.

"In the Devonian Period (400 million years back) beginning plants evolved to produce lignin, which in combination with cellulose, created wood which in turn for the first time allowed plants to grow tall for sunlight....fortunately for the future of life, white rot fungi evolved to produce the enzymes that can digest lignin and so the coal-making era came to an end. If it had not, CO2, which had already been drawn down for the first time in Earth's history to levels similar to today's, would have continued to decline until CO2 approached the threshold of 150 ppm below which plants begin first to starve, then stop growing altogether, and then die. Not just woody plants but all plants. This would bring about the extinction of most, if not all, terrestrial species, as animals, insects, and other invertebrates starved for lack of food. And that would be that. The human species would never have existed. This was merely the first time that there was a distinct possibility that life would come close to extinguishing itself due to a shortage of CO2."

Somehow, I have no doubt that, if CO2 levels trended toward "dangerously" low levels, we would find a way to add CO2 to the atmosphere.  We are very good at that.  It does strongly suggest, however, that humans do greatly depend on a stable atmospheric composition in order for life, as we know it, to persist.  We should consider that, regardless of the current debate on climate change.

Back to the geologists: Some even suggest using Anthropocene with a small “a”, i.e. “anthropocene” and using it informally. As attractive as that may be, it is not likely to be accepted as a suitable solution because it “is not consistent with geological community norms.” In the end, if the geologists want to start a new epoch based on human activity, they are required to identify the point at which human impact on earth became “geologically significant.”

 So, I would not be a bit surprised if they call the whole thing off. We wait with bated breath.