Scientists in the Anthropocene Working Group, a committee of the International Commission on Stratigraphy, recently revealed they had chosen Crawford Lake, a small lake in Ontario, as the official marker for a proposed new epoch: the Anthropocene. The sediments at the bottom of the lake provide a detailed record of human-induced environmental changes over time. One key marker — plutonium isotopes from 1950s nuclear tests.
The choice of Crawford Lake will be put forward in a formal proposal, which will also pinpoint the exact year this epoch started, in the hope of obtaining a final decision in 2024. W&M News discussed the importance of this decision with Nick Balascio, associate professor of geology at William & Mary.
Balascio’s research focuses on paleoclimatology, the study of geologic archives to understand past variations in Earth’s climate. With W&M professors Jim Kaste and Randy Chambers, in 2019 he published a study decoding the sedimentary history of Lake Matoaka, on the western edge of the W&M campus, in the journal Anthropocene.
The interview has been edited for length and clarity.
Q: How does your own work in Lake Matoaka relate to current discussions around the Anthropocene?
A: We can see a direct correlation between our very own Lake Matoaka and the site the AWC is setting up as the type locality for the Anthropocene. The radionuclides we found in Lake Matoaka are very similar to those found in Crawford Lake, allowing the identification of a peak in nuclear weapons testing through presence of fallout from nuclear weapons.
The focus of the research on Crawford Lake is the use of lake sediments as a geologic archive; this is also the focus of my research. I primarily work in the Arctic, where I recover lake sediment cores and study different physical or geochemical properties of those sediments as a natural history book of what has occurred in the environment.
As part of that research, I’ve also done some work locally, including in Lake Matoaka and other lakes in our area here in Williamsburg and the Peninsula. The Lake Matoaka record is somewhat unique for our area, and for Virginia in general, because it’s probably among the oldest mill ponds continuing to be maintained in the state. It was dammed around 1700 and it records the last 323 years of sedimentation and environmental conditions around the lake. Going down 30 centimeters in the sediment of Lake Matoaka, we identified a peak in a radioactive isotope of cesium, which was derived from atmospheric nuclear weapons testing from the 1950s and early 1960s.
Q: Not all geologists agree that Anthropocene should become a formal epoch. Why is this?
A: I think there are different ways to answer this question. What the AWG is proposing is an indicator for when humans started being the dominant force on the environment. Some people would argue that there are other ways or other indicators that might mark this transition throughout human history — such as the rise and expansion of agriculture thousands of years ago, the widespread presence of coal combustion particles in the environment following the start of the Industrial Revolution, or the recent widespread identification of plastics and microplastics in global environmental systems. So, this marker may oversimplify the interval at which people started to be the dominant force on the environment, discounting more of the history of human impact on their environment.
Another important point is that unfortunately we are impacting our environment in myriad ways — and maybe in the near future there will be even more consequential impact on the environment with an even greater global signature.
Q: How are specific years and sites selected to mark geologic boundaries?
A: Geologic boundaries are marked by major geologic transitions, and most often they’re marked by major paleontological transitions — meaning major extinction or speciation events, or the appearance or disappearance of significant life forms in Earth’s history. The magnitude of those differences corresponds to whether they mark a new era or epoch or period.
Then there are typic localities for these boundaries – sites located throughout the world where the boundaries were first identified or are most clearly expressed in a geologic formation, providing a basis for comparison to other locations. Crawford Lake has a very clear signal of radioactive fallout from atmospheric nuclear weapons testing starting in the 1950s that is preserved in annual sediment layers.
Q: If we officially enter the Anthropocene, what will change for us?
A: I expect the way we operate as scientists will not really change whether a new epoch officially starts, or whether this particular site is marked as its beginning.
However, entering the Anthropocene could be a powerful symbolic marker when it comes to issues such as environmental pollution or climate change. Energizing efforts to address these major issues would be a great thing.
Q: “The Anthropocene” has often become synonymous with “climate change” in public discourse. Is this too much of an oversimplification? Is there any pessimism embedded into this vision?
A: I think the association with climate change is undeniable and is part of human impact on our environment. Some may argue that the rise of greenhouse gases during the Industrial Revolution would also be a candidate for the marking of the Anthropocene.
In terms of your point about the pessimism, I think that all discussions around climate change or serious environmental impacts can be viewed through the lens of being pessimistic. I tend to view it more as a call to action.
Q: Do you think these human-made changes are already irreversible?
A: With some of the changes that we’ve caused — in particular, greenhouse gases in the atmosphere — it will take a very long time, in the absence of human activity, to return to a normal state. I think our best options now are to work to minimize and mitigate future impacts to our atmosphere as well as our environment.
In terms of geology of the planet, I don’t think there’s ever a worry that the planet won’t survive or that the geologic processes won’t continue. It’s more about how habitable the planet will be for humans and the impact on societies throughout the world.
Q: From your point of view, can an interdisciplinary approach to the Anthropocene be beneficial?
A: It’s important to have interdisciplinary perspectives on environmental issues, especially those that relate to human activity. A lot of my recent research is looking at prehistoric human-environment interactions, whether it’s humans modifying landscapes or responding to environmental change, either natural or human-imposed. There are interesting lessons to learn from the past about our relationship to the environment throughout time and their social, political, or cultural implications, especially as we grapple with these issues today.
There’s no doubt that having historical, anthropological and sociological perspectives on environmental issues is really important, whether they’ve happened within the last 50, 100 or 1000 years. And I imagine that the same things should be happening in discussing time periods which have specific geologic conditions defining them. Establishing time periods is a matter for geologists, but the far-reaching implications of those markers should be studied through an interdisciplinary lens.
Q: Going back to your Lake Matoaka work — is that research stream continuing?
A: With our Lake Matoaka work, we’ve shown a very local connection to the bigger-picture issue of the Anthropocene; but I don’t want it to overshadow other findings documenting post-1950s and 1960s phenomena.
Lake Matoaka is a really special place because of its history and association with William & Mary, its archive of environmental changes and its correlation to these globally significant events. We have ongoing work that is not only looking at radioactive pollution from the 1960s, but also at other environmental pollutants that have accelerated in recent decades, particularly from runoff and development in Lake Matoaka’s watershed. As many of us use the lake and the surrounding College Woods as a natural laboratory for our students as well as for recreation, I worry about these impacts and the future of Lake Matoaka. We will continue to keep our eye on it and I hope as a campus community we prioritize its health moving forward.
Antonella Di Marzio, Senior Research Writer