This interview series brings together Dave Murphy, an energy transition scholar, and physicist Tom Murphy, both founders of the Planetary Limits Academic Network (PLAN).
Across this series of discussions conducted by fellow founder Ben McCall, they explore a range of themes on the converging crises reshaping our world, including the polycrisis, ecological overshoot and the strengths and limits of modernity. Read Part One and Part Two.
Ben McCall: Dave, what do you think we can confidently assert about what a “sustainable” civilization would look like on the ~1000-year timescale? Are you inclined to agree with Tom’s perspective?
Dave Murphy: The population of the Earth was roughly 300 million in 1000 AD. One thousand years later, it is 26 times greater, at 7,800 million. I doubt that the planet’s population will be 26 times greater in 1000 years, reaching 202,800 million. That is about all I can confidently assert. I don’t think future societies will be anything like the past. I agree that we are now in a precarious position with a society built on stocks that are running low, but we are also transitioning to inexhaustible flows. The system we are moving towards is also much more efficient. What we disagree about seems less about whether the future will be different and more about what we know and don’t know about the future, and what we are to do about it now. So I see possibilities, but how those possibilities unfold is unknown.
I strangely think of the hawkish former Secretary of State and friend to few scientists, Donald Rumsfeld, whose musings about such prognostications are without parallel:
Reports that say that something hasn’t happened are always interesting to me, because as we know, there are known knowns; there are things we know we know. We also know there are known unknowns; that is to say, we know there are some things we do not know. But there are also unknown unknowns—the ones we don’t know we don’t know. And if one looks throughout the history of our country and other free countries, it is the latter category that tends to be the difficult ones.
Borrowing this analytical framework, I might suggest the following:
- Known-Knowns: There are planetary limits.
- Known-Unknowns: The scale and duration at which modernity can continue in the future based upon renewable energy.
- Unknown-Unknowns: I feel as though there is much that is unknown about the future, and we should be humble in our approach (e.g., nobody foresaw with any accuracy the timing and scale of the war in Gaza, or the rate of adoption of solar power). But I get the impression that the doomer’s perspective leaves less doubt. There is little room for anything unknown when the fate of modernity is “basically guaranteed.”
This conversation also reminds me of something I heard at a Peak Oil conference years ago. An investor was asked, “How do you think about long-term investing?” The investor’s reply was “I tend to think about getting the short-term right, and, over time, that means I get the long-term right as well.”
I bring this up simply to say that we need to think about civilization today and in the future, and hold them both equally. Just because it is hard to predict what might happen in the “messy decades-scale” view, doesn’t mean we should abandon hope for people today. Aren’t decisions made today civilization-relevant as well?
Ben: The picture Dave has implicitly painted here, of the possibility of a “neomodern” civilization that can persist for thousands of years relying on inexhaustible flows rather than depleting stocks, is certainly an appealing one! Dave has suggested that “the scale and duration at which modernity can continue in the future based upon renewable energy” is a known-unknown. Tom, I sense that you would disagree with that suggestion, or at least say there are known-known constraints on that scale/duration.
Tom Murphy: Right—I think we can say more about what is likely to succeed or fail. By definition, unsustainable systems (like modernity, I would say) are guaranteed to fail. Even centuries ago, when the scale of human activity was orders of magnitude lower, we were already ecologically unsustainable, as accumulating declines became apparent. The trends are now alarmingly steep: decidedly unsustainable and thus marching unambiguously toward failure.
I wish I could share optimism for inexhaustible flows and continued efficiency improvements—to great personal relief! But many factors intercede, for me. Energy—while very important to modernity—is only one part of the story. If any element critical to modernity is exhaustible, then it won’t matter if another is inexhaustible. For instance, even tireless energy flows like sunlight, wind, and the hydrological cycle are diffuse and require an enormous amount of “stuff” in the form of non-renewable materials to capture, convert, and store the energy. Ecologically harmful mining would therefore need to continue indefinitely (incompatible with planetary limits), to replace worn devices. Recycling is not an everlasting answer: it might extend the clock a few more centuries, but it can’t change the end result. Meanwhile, efficiencies already tend to be within a factor of two of theoretical limits, so not much gain remains in that quarter.
Beyond the confines of energy, modernity relies upon rapidly declining stocks and overtaxed flows in the form of aquifers, soils, materials, forests, and fish (to name a few)—sadly resulting in permanent, accelerating species loss. Meanwhile, enormous waste and pollution streams (beyond CO2) overwhelm the assimilative capacity of the ecosphere. Not only does the chimera of inexhaustible energy fail to address these dimensions, but it is also precisely the availability of large amounts of energy that drives these destructive trends. Powering modernity by alternate means could easily end up hurting more than helping, where it counts.
It is true that biology has figured out how to make indefinite use of inexhaustible flows, using a bare minimum of common minerals. But artificial systems are nowhere close to achieving such a feat in energy or any other domain. I don’t see us getting there, and certainly not soon enough to matter. To illustrate the gap, we are utterly incapable of running a controlled artificial ecosystem that can support human life, even for months, let alone indefinitely. Relatedly, the space station routinely replenishes its oxygen via costly rocket delivery from the surface so that inhabitants can breathe (aggressive recycling can’t keep up).
Humans are a powerful species, clearly capable of planetary exhaustion. It seems the only way we can live sustainably is by putting ecological health first and—through this lens—either rethink or abandon every human (cultural) construct. I doubt the result is something we would still call modernity.
As for feeling our way forward, I would prefer to avoid likely dead-end paths that could simply dig the hole deeper. My hope lies not in technological provision of the very energy that destroys environments, but in deciding that other goals are more important for humanity.
Ben: Dave, what do you see as the flaws in Tom’s argument here?
Dave: I am sorry to disappoint, Ben, but Tom’s perspective leaves little room for agreement.
First, energy and technology are neutral. The statement “precisely the availability of large amounts of energy that drives these destructive trends” is incorrect. The existence of donuts doesn’t drive weight gain; the decision to consume them does. The availability of large amounts of energy may enable destructive trends, but it does not drive them. Humans are steering the modernity spaceship. We are the ones choosing overexploitation of nature and trading that for short-term growth in GDP. We created these mental constructs, and we can create new ones that are more harmonious with nature.
Second, the statement “If any element critical to modernity is exhaustible, then it won’t matter if another is inexhaustible,” is clever trickery. The statement is true when taken in the abstract, but apply that as a hypothesis to the past 250 years, and it fails miserably.
For example, let’s propose this hypothesis:
H1: Horses are the most powerful tool in agricultural production.
If we tested this hypothesis in 1650 A.D., we would probably support it, but testing it today would clearly result in rejection.
Or, for another example, take this:
H2: Whale oil is critical for modernity.
Well, if this hypothesis were posed in 1850 A.D., then H2 would similarly be supported. Today? Not so much.
The point is this: the economy is evolutionary and adaptive; an element that is critical today might not be critical in 30 years. This ability to shift resources has been shown time and time again over the past centuries. Why do people keep ignoring the ability of the economy and human society to adapt to constraints? And before I get cast aside as a techno-utopian, let me state my views on this. I do not think that technology can solve humanity’s biggest challenges, but I don’t see them as limiting them either. I simultaneously hold the views that technology can alleviate many (if not most) of our resource and technical barriers to sustainability, while also holding that the biggest challenges we face are not solved by technology. They are not mutually exclusive views. Can these technologies provide a sustainable future? Yes – they can. Will we get there via technological invention alone? No.
We are avoiding the heart of the matter, which is summed, I think, in the following two questions:
First, what does it mean to be sustainable from Tom’s perspective? Inferring what I can from his comments, it seems that any human perturbation to natural ecosystems is unsustainable, or perhaps another way, any interruption to the natural energy flows through a natural ecosystem is inherently unsustainable. Modernity was unsustainable before the industrial revolution, according to his perspective, and now it is even more so. Not only is there no space in this view for what is described herein as modernity, but there also isn’t space for humans or any type of human society. Until we have a clear picture of what sustainability means, we will simply talk in circles.
Second, do we have an ethical obligation to other members of that Spaceship, i.e. society? Does each of us have an obligation to “love thy neighbor?” If so, what does it mean to love thy neighbor in this context?
The ultimate question, which brings us back to the beginning of this conversation, is whether we, as a species and society, can adapt in the future to become more sustainable, and perhaps, at some point, just plain old “sustainable.” Tom and I agree on one point: getting there will require cultural change. It is the “how” and the “what” that cause discord. That is, how human society will shift to a sustainable version of itself and what that sustainable version looks like. I disagree that we need to rethink or abandon all human cultural heritage. I think the solutions will come from building on that accumulated cultural knowledge, particularly from, for example, Indigenous communities that lived in harmony with nature for millennia. What do we humans gain from abandoning human culture, which is perhaps the defining characteristic of our species?
This interview has been edited and condensed for length. This interview is part of a series that features conversations between Dave Murphy and Tom Murphy on the polycrisis and planetary limits.
