Front Burner - Canada: the Anthropocene’s ground zero?

Episode Date: July 17, 2023

It's a well-established scientific fact that humans have had a massive impact on the planet. But has it been big enough to warrant the definition of a new geological epoch? It's an idea that's been hotly debated in the scientific community for years — and now, a group of researchers are arguing that a small lake in rural Ontario provides the best evidence for defining that new epoch. Crawford Lake, about 60 km southwest of Toronto, captures the history of the world in its sediment deposits, calcified like tree rings. Scientists say those layers show dramatic changes starting in the 1950s and that they mark a new geological epoch called the Anthropocene. Canadian Geographic contributing editor Alanna Mitchell explains the latest research, what makes Crawford Lake so special, and why defining the Anthropocene has been causing scientific controversy for more than two decades. For transcripts of this series, please visit: https://www.cbc.ca/radio/frontburner/transcripts

In the Dragon's Den, a simple pitch can lead to a life-changing connection. Watch new episodes of Dragon's Den free on CBC Gem. Brought to you in part by National Angel Capital Organization, empowering Canada's entrepreneurs through angel investment and industry connections. This is a CBC Podcast. Hi, I'm Tamara Kandaker. Tamara Kandaker. There were marine sediment sections in Japan and in the Baltic Sea off the coast of Germany and Scandinavia. There was a lake in California, a lake in China. Francine McCarthy is a geologist at Brock University and a member of the Anthropocene Working Group, an international network of scientists who've spent the last four years

searching the planet for one very specific location. We, the Anthropocene Working Group, since 2018, has been looking for the best place on the planet to characterize what the planet is like now and has been since the mid-20th century compared to what it has been like since the ice sheets melted almost 12,000 years ago. On Tuesday, the group announced that after a global search, they'd found it. Right here in Canada, at Crawford Lake in Milton, Ontario. The word that's usually used, I think, to describe it is unassuming. It's pretty, but it's not spectacular. What Crawford Lake lacks in awe, it makes up for in geological significance.

Or at least, that's what the Anthropocene Working Group believes. They say the sediments at the bottom of the lake hold a record of the Earth's history. And more than that, they hold evidence that we've entered a new geologic chapter, the Anthropocene. A tipping point was reached. The switch was flipped. It's a different system. It will not go back to the way it was, which is why we want to call it by a different name. The discoveries made international headlines, and it sparked debate among scientists. They're divided on whether it really does say we've entered a new epoch. A century ago, it was very much felt that humans really had negligible impact on nature.

Nature was so big, how could we possibly make a big change to this? What we're saying in effect by defining an Anthropocene is to say no actually humans are a major geological force and if anything probably the most significant geological force on the planet. McCarthy and her colleagues argue that recognizing the markers of the Anthropocene at Crawford Lake would send a message that shouldn't be ignored. In all of its 4.6 billion year history, never has the Earth changed so much, so fast. Anyone who has children and grandchildren should recognize that that trajectory, if it's not checked, the world that at least their grandchildren will inherit may not be a hospital world for humans. So today on FrontBurner, what is the significance of the discovery at Crawford Lake? What did the working group find there? Does it mean we're in a new epoch?

And why can't scientists agree on what it all means? Alana Mitchell is here with me. She's a science journalist, author, and contributing editor at Canadian Geographic. Hi, Alana. Thanks so much for doing this. It's my pleasure. So before we get into what the researchers have found, we're going to be using the term Anthropocene a lot. And I wonder, can you just break down for us what it means? Okay. So to a geologist, what it means is a new, potentially a new epoch in the Earth's crustal history. So a marker in the Earth's crust that tells us that we've entered into a whole new timeframe, a whole new chapter of Earth's history.

And this concept of the Anthropocene as a new age defined by human behavior, of the Anthropocene as a new age defined by human behavior. It's been kicking around for years now, but formally defining it as a geological epic has taken some time, right? And why is that? Well, it's been around since the year 2000, when the Nobel Prize-winning chemist, Paul Crutzen, just came up with the term because he said, you know, we're entering into a whole new planetary system and it's being caused by the actions of humans. And so, you know, this phrase, the Anthropocene just sort of emerged into the geological literature and it captured the public imagination, the scientific imagination, the cultural imagination. And so, then the stratigraphers who are this very, I mean, let's face it, an obscure group of scientists who define the age of the planet and the different

stages of its evolution by looking at the crust, typically, they said, well, let's see if we can see the mark of humanity in the crust. And if we can, then we can figure out a whole new nomenclature for the time of the planet's history that we're in. Scientists say the onset of an Anthropocene would mark the end of the Holocene, the current epoch that began almost 12,000 years ago as the last ice age ended. Right. And so what have been the challenges around doing that? Well, one of the challenges around doing that? Well, one of the major challenges is that stratigraphers are very conservative, and they weren't sure that they wanted to be able to capture this or that it was time to capture it.

I mean, these are people who look at, you know, tens of thousands of years off and millions of years. They look at time as it's laid down in the crust of the planet, the 4.6 billion year history of the planet. And so if they look at the effects of humanity on the planet, some of them are saying, yeah, we're not so sure it's really there. They weren't convinced. And so there was this whole, almost a decade, I mean, from 2000 to roughly 2009 of thinking about whether it was appropriate to even really launch the examination. And then in 2009, they set up this thing called the Anthropocene Working Group. This is the international body of stratigraphers who set the geological time scale. They set up a working group and said, OK, look at it and see if you really think there is enough evidence in the crust itself for us to even be thinking about this.

And the Anthropocene working groups said eventually you know it took another decade and they said you know what we think there is enough and so then the quest the global quest began to try to find which piece of the crust you know was the best representative of this time. 12 sites were identified, studied and debated, and now Little Crawford Lake in Ontario has been chosen as the golden spike, the ideal marker showing where one epoch ends and another begins. So what makes the Anthropocene unusual or unique from the previous epochs? Well, this one is, it's not absolutely unique, but it's one of the very, very few that

you can point to in the geological record that is caused by a single species. So you can point to, for example, when cyanobacteria 2 billion years ago, I think it is, changed the composition of the atmosphere. So they started to eat carbon and produce oxygen. And so all of a sudden, of the atmosphere. So they started to eat carbon and produce oxygen. And so all of a sudden, you had a different atmospheric composition. And so different creatures began to evolve. So that was an example of a single type of creature changing the fate of the planet. And that's what geologists are saying is happening now, that our species, a single species, is changing the future of our planet. What this group of stratigraphers is saying is that it started in the mid-1950s, but that's

what they call the boundary of it. So it could go for millions of years, it could go for tens of millions of years, it's just unclear. What they're saying is that something changed irrevocably and that we cannot go back to what we were before. The planet has entered a new phase of its life, that the systems, you could say the operating systems of the planet are different now, and they will never be the same as they were before the 1950s. The last official epoch is the Holocene, which started around 12,000 years ago after the end of the last major ice age. But for the last few decades, there is a group of scientists that's been proposing that we've actually entered a new epoch known as the Anthropocene. And the Anthropocene is defined by humans being the primary drivers of geological change. And so what have scientists been doing to confirm that?

Well, they've been looking for really good examples of how to tell the difference between the Holocene and the Anthropocene. So they've been looking for chunks of the crust, for example, ice in Antarctica. They've been looking at corals. They've been looking at lakes. They've been looking at other different bits and pieces of the earth's crust to see not just if they can find the markers of this new epoch, but also a very, very tightly laid down timeline. So what they wanted, what they actually wanted was a year. They want to be able to point to the summer of 1950 or whatever it is that they're eventually going to point to and say, that was the moment that we passed the point of no return. That was the moment everything changed. And they wanted a global best example of that against which all

other samples of the crust could be tested. So that global best example, that's what's called a golden spike, right? What's a golden spike exactly? It is the exemplar, the absolute global best example of this new epic that they're looking for. And there are golden spikes throughout the stratigraphic chart. So there are dozens and dozens of them that demarcate when one era or one age or one epic or whatever it is that we're looking at, when one began and when one ended. So in the intro, we heard Francine McCarthy describe some of the 12 sites that were up for consideration as the Golden Spike. And they included some coral reefs, a peat bog, an ice sheet.

But what they've landed on is Crawford Lake in Ontario. Just 10 minutes from Canada's busiest highway sits this serene lake, which holds the secrets of human history. It's about 60 kilometers west of Toronto, close to Guelph. It's in Ontario's Niagara Escarpment, which is a conservation area. And I understand it was already on scientists and archaeologists' radar even before the Anthropocene epoch was even being discussed, right? Why is that? Oh, because it's an incredibly unusual lake. In fact, the conservation authority that now owns the lake and the land surrounding it got hold of this thing and I think bought it in 1969, as I understand it. And it was because it was just such a tiny, perfect lake. And then

once they started doing the scientific investigation into Crawford Lake, they realized that it's a meromictic lake, which is a very, very rare type of lake. It means that it's so deep and so small in area at the top that there's a bottom layer that never mixes with the top layer. So what you get is this beautiful, perfect year-by-year record of sediments at the bottom of the lake. And so what is it about Lake Crawford versus the other sites that were up for consideration that scientists believe make it the golden spike? Well, one of the main things is that because it's this meromictic lake that has these beautifully laid down sediments that haven't been disturbed. And because each layer for each year is sort of sealed, they call it laminated, laminated with calcite, which is a type of calcium.

Each single layer, so each single year, in other words, is very, very easy to discern. Beneath its surface, Lake Crawford holds a geological treasure, layered sediment which captures humanity's impact on the planet year after year, including microplastics, fossil fuel burning, and even the plutonium from bomb tests. So you can go back in the record and say,

okay, this was 1952 in the winter, and this was, you know, 1834 in the summer, and, you know, if you think about tree rings, this is the equivalent in the earth's crust of a tree ring. You can really go back and see every single, every single year in exquisite detail. So it has all the markers of the Anthropocene, which are things like, you know, the change in the composition of the atmosphere to reflect the load of carbon. You have, you know, industrial activity. You have change in the composition of the atmosphere to reflect the load of carbon. You

have, you know, industrial activity, you have change in the creatures that are living in the lake, you have all of these changes that represent, that characterize the Anthropocene. I know they were also looking for markers of a period called the Great Acceleration. What is that? And what markers of that did they find? Right. And so there was this whole discussion for a couple of decades really about when would the Anthropocene begin? Was it when somebody fired up the first coal-fired engine? Was that the time, the 1700s? Was it before that? They decided that really, the time that the planet entered this period of no return was what they called the Great Acceleration.

So that was in the middle of the 20th century after the Second World War when human population just exploded, when industrial activity exploded, when plastics came on the scene, when the carbon load in the atmosphere just began to rise very, very dramatically. So life as we know it on the planet changed because of all this activity. So what they were looking for was very profound and very abrupt change. You mentioned the depth of Lake Crawford. And just briefly, how did scientists collect samples from the core there and test them? Oh, well, they have to send a corer down to the very bottom of the lake. And what they did with this one, because if you just put down a sort of a hollow thing and pull up a corer, it just disintegrates because it's all full of gas. Once you get it up to the surface,

it just, you know, it's all sludge. So they wanted these layers to be in perfect, perfect shape. And so what they did was put down a freeze corer. So it's a corer that is filled with dry ice and the dry ice makes the face of this thing very, very cold. And then the sediments adhere to it and they come up in this perfect, perfect spike. It's just amazing to see the pictures on this. And Crawford Lake is a culturally important site for Indigenous people in the area, from what I understand. So how were they involved in the process of collecting these samples? Right. Well, one of the fascinating things about the early research on Crawford Lake is that as they realized it was meromictic and therefore had all these beautiful sediments,

they thought, oh, what will we find in these sediments? And in the 1970s, some of the earliest research on this lake discovered corn, the corn pollen. And that meant that there had to have been a settlement somewhere around Crawford Lake in the 1400s and 1500s. And that was long before colonization, so that had to this very extensive Indigenous settlement on the lake at one time, and that it ended. In order for Dr. McCarthy to get her final core, she sought and received permission from the Indigenous communities to take a core. And she told me that it's probably going to be the very last core that anybody will ever take out of that lake, because to the Indigenous people who are caregivers of the lake,

they consider the lake to have a personality. And it was very painful for them to give permission for this core to be taken. So they are the keepers of the soul of the lake. In the Dragon's Den, a simple pitch can lead to a life-changing connection. Watch new episodes of Dragon's Den free on CBC Gem. Brought to you in part by National Angel Capital Organization, empowering Canada's entrepreneurs through angel investment and industry connections. Hi, it's Ramit Sethi here. You may have seen my money show on Netflix.

I've been talking about money for 20 years. I've talked to millions of people and I have some startling numbers to share with you. Did you know that of the people I speak to, 50% of them do not know their own household income? That's not a typo. So the idea that the Anthropocene is a new epoch, that we've left the Holocene epoch and started a new one, this is controversial among geologists. Why is that? Ah, it's incredibly controversial among geologists. and it's controversial in sort of two different ways. On one hand, you have very conservative stratigraphers who are geologists who look at the sediments in the core. It's a very, very rigid, quite a bureaucratic enterprise.

And they say, some of them are saying, well, you know, we don't have enough evidence that this is irrevocable, that we have actually moved past something that cannot be healed in the in the crust there's not enough evidence there that we've that we've actually passed the point of no return and then there are other people who say wait a sec if you define it as an epoch as opposed to something like an event a geological event which is much more sort of less precise to the crust, but more global and more meaningful and more intense and reaches much further than just the crust, but reaches into the cultural and the social elements of our planet. They say that declaring an epic is too

small an act. So there's some who say it's too big an act, and some who say it's too small. Yeah, I was wondering if I could get your thoughts on something else that Francine McCarthy said, which is related to what you were just saying, which was that having the Anthropocene acknowledged by the International Commission on Stratigraphy as an epoch of its own would be a big deal because it would send a message. We feel that having that very conservative and reluctant body put a line on that timescale would send a very clear signal to the world at large that, yes, indeed, there is no more denying this change. What do you think are some of the broader political implications of accepting the

Anthropocene as a new epoch? Well, I'm not sure about the political implications, but the social and cultural implications are massive. Whether politicians end up listening to that is a whole different question. But what it tells us is that really that we have done as a species inadvertently we have done something that is um that has changed the face and the fate of our planet and we can never go back to a time before we made this change and and i think it's it's kind of humbling you know to me it's kind of uh that we could have done this and had it be so profound that it changed the course of the planet is something that I think we all have to sort of take to heart. I think it's going to make a difference. So the Anthropocene Working Group has chosen Crawford Lake as the golden spike, but it's not official yet, right?

It still has to go through several more rounds of voting by other bodies, regardless of what happens. What kind of impact has this conversation already had on the scientific community? Well, it's required the scientific community to look pretty deep into this frontier of change. So naming a new epoch in this very, very precise way, so a stratigraphic way, is a signal, I guess, to the rest of the scientific community that this is a pretty serious moment. This is not just business as usual. The fact that the Anthropocene is being proposed as an epoch, despite how little time has passed and that we're still living in it. What does that say about the impact humans are having on the planet? Well, it's been a catastrophic impact. We've changed the conditions of life on our planet, and we've changed them irrevocably. And the question then becomes, you know, how does our species adapt to that? How do other species adapt to this new time that the planet has entered? And

you have to look to a lot of the unknowns that this raises. It's one thing if you're a geologist to look back in time and say, you know, what happened as a result of a change like the one that they're describing in today's crust. But it's something else to say, okay, we have already changed things to this degree, and now what happens? And that's something that no scientist anywhere in the world can know for sure. Alana, thank you so much for this conversation. This was really fascinating.

I appreciate it. Pleasure. All right, that's all for today. I'm Tamara Kandaker. Thank you so much for listening to FrontBurner. For more CBC Podcasts, go to cbc.ca slash podcasts.