You say Holocene, I say Anthropocene.
Two AAPG authorities say the renewed buzz for naming a new epoch in earth history seems premature.
A pair of recent papers in international publications call for naming a new epoch – the Anthropocene – acknowledging the wholesale impact humans have had on the planet.
One paper, published in the February issue of GSA Today, suggests the last 200 years of industrialization will provide an undeniable stratigraphic marker for future geologists.
Some of the effects cited include climate change, major changes in soil erosion and deposition patterns, changes to the carbon cycle, ocean acidification, altered flowering times among plants and new animal migration patterns.
The other paper, published in the journal Soil Science, pushes the dawning of the Anthropocene back a few thousand years to the beginnings of agriculture and a resulting decline in soil fertility.
Nobel chemistry laureate Paul Crutzen coined the term Anthropocene in 2000, and the similar Anthrocene was bandied about by scientists as early as the late 1800s, according to an article in the online publication Live Science.
So it’s really not a new idea – unless you’re speaking in geological terms.
Defining the Boundaries
That’s one of the things that concerns Don Owen and Art Donovan, AAPG members on the North American Committee for Stratigraphic Nomenclature.
Massive human intervention on the planet may be undeniable, but “it’s not going to show up on a geological time scale” yet, Owen said.
When the earth’s entire history is presented graphically, as on a timeline, “You can barely see the Holocene,” Donovan said. Measured from the end of the last Ice Age, the Holocene is generally measured at 10,000 years old and encompasses all human activity.
Another problem with declaring the end of the Holocene is that “nobody agrees on the boundaries” for the new epoch, said Owen, chair of the AAPG delegation on the NACSN and a subcommittee member of the International Commission on Stratigraphy, the final arbiter for naming rocks and times.
Donovan agreed that “proponents can’t agree” where to draw the line.
“Even the guys pushing it are all over the place,” he said.
Suggestions include 1874 (marking the invention of the steam engine), 8,000 years ago at the beginning of agricultural activity or perhaps the extinction of some key species linked directly to human activity.
Owen said the beginning of the Cambrian Age is pegged at 542 million years ago, and earlier epochal divisions are less specific, based on broader data or fossil records.
In more recent times, geologists are able to see changes more clearly, he said.
Experts talk of driving a “golden spike” into the rocks where major changes, such as extinctions, are delineated, he said.
“We know the fossils on both sides ... and have good radiometric data,” Owen said.
Donovan said deciding what physical data to use – continental, marine, ice cores – can be a concern.
An unsettled debate regarding the 1.8 million-year-old Quaternary Period, or era, is an example, Donovan said.
“There’s no evidence in the marine record,” he said. “The paleomagicians can’t see anything that ties in.”
Sometimes opinions split along academic vs. industry lines, Donovan said.
A Matter of Scale
The decades-long controversy points at the problem in gaining consensus and shows why some scientists don’t see the urgency in naming a new epoch.
“The problem is scale,” Donovan said. “On an anthropological time scale, it makes sense to acknowledge massive human intervention.”
On a geologic scale, however, “It’s really insignificant,” he added.
Owen said the term “age” might be more acceptable than “epoch” for the young Anthropocene.
“Sometimes things change in rank,” he said, adding that soil infertility “may be one of the best arguments” in favor of naming a new age.
“If you’re talking about anthropology, then you can do something like this,” Owen said.
In the end, the question is whether the term becomes widely accepted by the scientific community,” he said.
“Sometimes informal terms get recognized,” he said. “Just because there’s a difference of opinion doesn’t mean it’s wrong.”