Digging Up the Anthropocene

29 November 2017

Wednesday


Photograph by Ben Roberts.

A recent paper, The Working Group on the Anthropocene: Summary of evidence and interim recommendations, by Jan Zalasiewicz and twenty-four additional authors, considers the case for the formalization of the Anthropocene as a chronostratigraphic/geochronologic unit, i.e., a periodization of geological time. Since “Anthropocene” was proposed by Paul Crutzen in 2000 as a geological period marked by the impact of human beings upon the Earth, geologists have been attempting to determine if the geological record will someday bear the distinctive traces of human activity and whether (and this an interesting future contingent) geologists might someday be able to reliably locate and identify the Anthropocene boundary in the geological record. The emerging consensus is that there is, “…a clear synchronous signal of the transformative influence of humans on key physical, chemical, and biological processes at the planetary scale.” These synchronous signals are described as follows:

“A range of potential proxy signals emerged as potentially important during the analysis, for instance the spherical carbonaceous particles of fly ash (Rose, 2015; Swindles et al., 2015), plastics (Zalasiewicz et al., 2016), other ‘technofossils’ (Zalasiewicz et al., 2014a, 2016) and artificial radionuclides (Waters et al., 2015), changes to carbon and nitrogen isotope patterns (Waters et al., 2016) and a variety of fossilizable biological remains (Barnosky, 2014; Wilkinson et al., 2014). Many of these signals will leave a permanent record in the Earth’s strata.”

The Working Group on the Anthropocene: Summary of evidence and interim recommendations, by Jan Zalasiewicz, et al., Anthropocene, Volume 19, September 2017, Pages 55-60.

Will paleontologists of the future someday dig up technofossils, and from these technofossils attempt to reconstruct an entire technological infrastructure, much as we today reconstruct an extinct species from a single preserved vertebra or rib, and around the resulting organism we seek to reconstruct the entire vanished ecosystem in which that extinct species made its home?

Recently I was prompted to think about the Anthropocene from a paleontological perspective by a Twitter post by Ben Roberts, which included images of automobiles being degraded by weathering (these photographs are included in this post). In response to these images I wrote that I would like to see what the fossils of these automobiles would look like in ten million years. This caused me to think about the possibility of the artifacts of human civilization that might be preserved over geological scales of time. The signals mentioned above in the paper quoted all constitute microfossils that would begin to appear in the geological record for the first time with the advent of the Anthropocene, but I also wonder if larger artifacts might be preserved in the geological record.

Photograph by Ben Roberts.

The tissues of organisms — sometimes even soft tissues — are preserved in the geological record through several different processes. While it is unlikely that human artifacts would be fossilized by replacement and recrystallization or by adpression, it seems possible that technological fossils could be formed through permineralization or through casts and molds. It is easy to imagine that the hulk of an automobile, a train, or even an entire industrial facility might fill with sediment, and though the steel would rust away, that rust would be preserved in situ more or less in its finished form by the sediment hardening into sedimentary rock around it. A careful paleontologist thus might be able to excavate an entire locomotive by means of rust encased in sedimentary rocks.

Of course, fossils are rare, and most artifacts will be eroded away rather than fossilized. Moreover, technofossils are likely to be even more rare than natural fossils. Given our interest in our own past, and our technological abilities to recover artifacts, human beings will continually recover our own remains from the historical period. The fossil record that remains to be discovered will depend upon whether civilization is merely transient or whether it will prove to be enduring. In the case of civilization being a transient historical phenomenon (note that civilization could endure for another 10, 20, or 30 thousand years or more and still be “transient” from the perspective of paleontology), the process of recovering artifacts that would otherwise be fossilized will come to be end. There likely will be a few cases at least of human artifacts in sedimentary basins that eventually are preserved by some process or another. Human artifacts will ultimately be preserved in ice, in snow, in a glaciers, covered in sand on beaches and deserts, covered by landslides on land, as well as being preserved in the oceans, in deep, cold anoxic waters, as well as underwater covered in mud. There is a good chance that many ancient ships lost at sea have been entirely covered over by sand, mud, and silt, and are not likely to be located within our own historical period, thereby saved for far future paleontologists specializing in the excavation of technofossils.

Photograph by Ben Roberts.

Human beings have been building structures and leaving artifacts for thousands of years, of course — sufficient time for many of these structures to be abandoned, covered over, forgotten, and subsequently revealed once again to the light of day by archaeology. The extensive remains of the Indus Valley civilization were forgotten in this way, only to be rediscovered in the twentieth century, and the knowledge of the Minoan civilization had been reduced to mere legend when its palaces were eventually excavated. These remains have been subject to weathering and degradation, but some are in a remarkable state of preservation, though they have not been buried for millions of years, or subjected to the temperatures and pressures that result from being contained in geological strata. An insufficient time has passed for there to be a fossil record of human civilization, even though there is an archaeological record of human civilization.

Up until the industrial revolution, human industry was mostly carried out on a modest scale and resulted in little impact on the environment. Most materials employed were biodegradable and have disappeared over scales of historical time. I have previously observed that traces of Roman lead production have been preserved in the ice of Antarctica, and I would not be surprised to learn that silver processing at Potosí in the early modern period also left detectable traces. One might understand these examples as very early anticipations of later industrial processes carried out on a far larger scale. With the advent of technologies made possible by the systematic application of science to industry, new and unprecedented materials were invented and employed in industrial-scale applications. Some of these are the materials cited in the paper quoted above as the distinctive signals of the Anthropocene. While the recent paper cited above singled out a spike of artificial radionuclides, an earlier paper specifically mentioned plastics:

“Plastics are already present in sufficient numbers to be considered as one of the most important types of ‘technofossil’ that will form a permanent record of human presence on Earth.”

“The geological cycle of plastics and their use as a stratigraphic indicator of the Anthropocene,” by Jan Zalasiewicz, et al.

Contemporary industrial processes are sufficiently sophisticated to produce distinctively new technogenic materials (like Chernobylite) and on a scale to distribute the products of industry globally, and so to leave a planetary trace of human activity. It remains only for time, heat, and pressure to transform these distinctive traces into technofossils.

Photograph by Ben Roberts.

That the global deposition of a distinctive Anthropocene layer begins in earnest in the twentieth century (and specifically in the mid-twentieth century) is significant. The authors of the paper write:

“This mid-20th century level seems to serve best the prime requirement for a chronostratigraphic base of high-precision global synchroneity… Human activities only came to have an effect that was both large and synchronous, and thus leave a clear (chrono-) stratigraphic signal, in the mid-20th century. A wide range of evidence from this time indicates the rapid increase in scale and extent of global human impact on the planetary environment, also clearly recognizable from a wide range of synchronous stratigraphic indicators.”

The Working Group on the Anthropocene: Summary of evidence and interim recommendations, by Jan Zalasiewicz, et al.

It is interesting to note how this mid-20th century boundary (as geologists would call it; I might call it a “threshold”) corresponds to other boundaries (or thresholds) in human development. For example, in the Before Present (BP) time scale frequently employed in the sciences, the “present” for purposes of radiometric dating has been set as 01 January 1950, as radiometric dating became practical at about this time. A neat mid-century point of reference fit well with the actual date of the availability of the technologies of radiometric dating.

Recently in Radio Technology and Existential Risk I discussed what we may call “Sagan’s Thesis,” viz. that nuclear and radio technology are tightly-coupled, so that the invention of radio technology means both that the inventors of the technology can see and be seen in the cosmos, and that the inventors soon will be able to build nuclear weapons and so be enabled to destroy themselves. Radio, then, is both an existential risk and an existential opportunity, thus marking a threshold of technological maturity in the history of an intelligent species:

“Radio astronomy on Earth is a by-product of the Second World War, when there were strong military pressures for the development of radar. Serious radio astronomy emerged only in the 1950s, major radio telescopes only in the 1960s. If we define an advanced civilization as one able to engage in long-distance radio communication using large radio telescopes, there has been an advanced civilization on our planet for only about ten years. Therefore, any civilization ten years less advanced than we cannot talk to us at all.”

Carl Sagan, The Cosmic Connection: An Extraterrestrial Perspective, Chap. 31

While radio astronomy sensu stricto is not likely to leave any trace in the fossil record (though the wreckage of radio telescopes might be found), it will leave a lasting mark on civilization, and may (under some circumstances) transform a civilization. A changed civilization that endures for geological scales of time will leave a transformed trace of itself in the geological record. And for humanity, this change began near the mid-20th century boundary — about the same time as we began to use nuclear weapons, which is consistent both with Sagan’s Thesis and with a mid-20th century boundary for the Anthropocene.

The consilience of these several factors — planetary-scale anthropogenic impacts, radio technology, and nuclear technology (which includes both nuclear weapons and radiometric dating) — distinctively manifesting themselves on a global scale in the middle of the twentieth century, constitute “synchronous signals” not only for stratigraphy, but also for civilization on historical scales of time. In other words, the Anthropocene marks not only a geological periodization, but also a new stage in the development of civilization.

Train cemetery, Uyuni, Bolivia

In his original 1964 paper that introduced the idea of “types” of civilization, “Transmission of Information by Extraterrestrial Civilizations,” Kardashev defined a Type I civilization as a civilization at, “a technological level close to the level presently attained on the earth.” (Here I ask the reader to set aside imaginative characterizations of Type I civilizations that have been elaborated by individuals who have never bothered to read Kardashev’s paper.) As this paper was written in 1964, a mid-20th century boundary for the Anthropocene corresponds nicely with the level of technological development close to that attained by civilization at this time. We could, then, identify a Type I civilization with a civilization that produces an Anthropocene-like boundary on its homeworld (i.e., the equivalent of the Anthropocene for some other intelligent species but defined in an non-anthropocentric way).

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How to Live on a Planet

27 September 2017

Wednesday


Humanity is learning, slowly, how to live on a planet. What does it mean to live on a planet? Why is this significant? How has our way of living on a planet changed over time? How exactly does an intelligent species capable of niche-construction on a planetary scale go about revising its approach to niche construction to make this process consistent with the natural history and biospheric evolution of its homeworld?

Once upon a time the Earth was unlimited and inexhaustible for human beings for all practical purposes. Obviously, Earth was was not actually unlimited and inexhaustible, but for a few tens of thousands or hundreds of thousands of hunter-gatherers distributed across the planet in small bands, this was an ecosystem that they could not have exhausted even if they had sought to do so. Human influence over the planet at this time was imperceptible; our ancestors were simply one species among many species in the terrestrial biosphere. Even before civilization this began to change, as our ancestors have been implicated in the extinction of ice age megafauna. The evidence for this is still debated, but human populations had become sufficiently large and sufficiently organized by the upper Paleolithic that their hunting could plausibly have driven anthropogenic extinctions.

In this earliest (and longest) period of human history, we did not know that we lived on a planet. We did not know what a planet was, the relation of a planet to a star, and the place of stars in the galaxy. The Earth for us at this time was not a planet, but a world, and the world was effectively endless. Only with the advent of civilization and written language were we able to accumulate knowledge trans-generationally, slowly working out that we lived on a planet orbiting a star. This process required several thousand years, and for most of these thousands of years the size of our homeworld was so great that human efforts seemed to not even make a dent in the biosphere. It seemed the the forests could not be exhausted of trees or the oceans exhausted of fish. But all that has changed.

In the past few hundred years, the scope and scale of human activity, together with the size of the human population, has grown until we have found ourselves at the limits of Earth’s resources. We actively manage and limit the use of resources, because if we did not, the seven billion and growing human population would strip the planet clean and leave nothing. This process had already started in the Middle Ages, when many economies were forced to manage strategic resources like timber for shipbuilding, but the process has come to maturity in our time, as we are able to describe and explain scientifically the impact of the human population on our homeworld. We have, today, the conceptual framework necessary to understand that we live on a planet, so that we understand the limitations on our use of resources theoretically as well as practically. When earlier human activities resulted in localized extinctions and shortages, we could not put this in the context of the big picture; now we can.

Today we know what a planet is; we know what we are; we know the limitations dictated by a planet for the organisms constituting its ecosystems. This knowledge changes our relationship to our homeworld. Many definitions have been given for the Anthropocene. One way in which we could define the anthropocene in this context is that it is that period in terrestrial history when human beings learn to live on Earth as a planet. Generalized beyond this anthropocentric formulation, this becomes the period in the history of a life-bearing planet in which the dominant intelligent species (if there is one) learns to live on its planet as a planet.

In several posts I have written about the transition of the terrestrial energy grid from fossil fuels to renewable resources (cf. The Human Future in Space, The Conversion of the Terrestrial Power Grid, and Planetary Constraints 9). This process has already started, and it can be expected to play out over a period of time at least equal to the period of time we have been exploiting fossil fuels.

I recently happened upon the article How to Run the Economy on the Weather by Kris De Decker, which discusses in detail how economies and technologies prior to the industrial revolution were adapted to the intermittency of wind and water, and the adaptability of such habits to contemporary technologies. And I recall some years ago when I was in Greece, specially the island of Rhodes, every house had solar water heaters on the roof (and, of course, sunshine is plentiful in Greece), and everyone seemed to accept as a matter of course that you must shower while the sun is out. A combination of very basic behavioral changes supplemented by contemporary technology could facilitate the transition of the terrestrial power grid with little or no decline in standards of living. This is part of what it means to learn to live on a planet.

As we come to better understand biology, astrobiology, ecology, geology, and cosmology, and we thus come to better understand our homeworld and ourselves, we will learn more about how to live on a planet. But the expansion of our knowledge of exoplanets and astrobiology will be predicated upon our ability to travel to other worlds in order to study them, and if we are fortunate enough to endure for such a time and to achieve such things, then we will have to learn how to live in a universe.

The visible universe is finite. Though the visible universe may be part of an infinitistic cosmology (or even an infinitistic multiverse), the expansion of the universe has created a cosmological horizon beyond which we cannot see. I have previously quoted a passage from Leonard Susskind to this effect:

“In every direction that we look, galaxies are passing the point at which they are moving away from us faster than light can travel. Each of us is surrounded by a cosmic horizon — a sphere where things are receding with the speed of light — and no signal can reach us from beyond that horizon. When a star passes the point of no return, it is gone forever. Far out, at about fifteen billion light years, our cosmic horizon is swallowing galaxies, stars, and probably even life. It is as if we all live in our own private inside-out black hole.”

Leonard Susskind, The Black Hole War: My Battle with Stephen Hawking to make the World Safe for Quantum Mechanics, New York, Boston, and London: Little, Brown and Company, 2008, pp. 437-438

We know, then, scientifically, that the universe is effectively finite as our homeworld is finite, but the universe is so large in comparison to the scale of human activity, indeed, so large even in comparison to the aspirational scale of human activity, that the universe is endless for all practical purposes. Though we are already learning how to live on a planet, in relation to the universe at large we are like our hunter-gather ancestors dwarfed by a world that was, for them, effectively endless.

Only at the greatest reach of the scale of supercivilizations will we — if we last that long and achieve that scale of development — run into the limits of our home galaxy, and then into the limits of the universe, at which time we will have to learn how to live in a universe. I implied as much in an illustration that I created for my Centauri Dreams post, Stagnant Supercivilizations and Interstellar Travel (reproduced below), in which I showed a schematic representation of the carrying capacity of the universe. At this scale of activity we would be engaging in cosmological niche construction in order to make a home for ourselves in the universe, as we are now engaging in planetary-scale niche construction as we learn how to live on a planet.

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