This interview 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 the whole series: Part One | Part Two | Part Three | Part Four | Part Five
Ben McCall: Dave, you’ve often expressed optimism about humanity’s future despite the planetary limits we face. What makes you optimistic?
Dave Murphy: First, I would frame the issue differently. As written, it posits an optimistic outlook for the future vs. some “scientific” issue of planetary limits. These two should not be viewed in this way. There are indeed planetary limits. The second issue is the outlook I choose to take for the future, which is based on nothing scientific at all. I guess my point is that these two things are not mutually exclusive; one can understand planetary limits and be optimistic.
Second, why am I optimistic? I would say that a tremendous amount can be accomplished in the middle ground between techno-utopian and doomer. This middle space can simultaneously acknowledge planetary limits and the dangers associated with deforestation, species decline, climate change, etc., and advocate for positive change in our energy systems. It has also been my experience that despair and doomerism are ineffective change-agents. No politician is elected on a slogan “It’s all over.” But the real reason I am optimistic is probably pretty simple: I have kids, and I can’t tell them the world is over before they even grow up.
Ben: Tom, what degree of optimism do you have about humanity’s future? How does your perspective contrast with the one Dave has expressed here?
Tom Murphy:I make a distinction here between humanity’s future and modernity’s future. Many people conflate the two. As I see it, the brief flash of modernity is incompatible with planetary limits and will necessarily terminate one way or another. For this reason, I no longer focus on energy systems, since keeping modernity powered does not seem to be an appropriate goal—essentially kicking the can down the road. Access to a large amount of exosomatic energyis exactly what has enabled modernity to carry out its atrocities against the more-than-human world via deforestation, habitat fragmentation, extermination, and extinction—and to swell human populations to precarious heights via industrial agriculture. Technological innovations, such as renewable energy, tend to enhance—or at least sustain—our destructive practices, irrespective of CO2 levels. Unless we change something deeper, we can expect more of the same behaviors and outcomes.
So, where is the optimism in all that? It’s simply that humans do not have to operate this way on the planet, as many amazing people have demonstrated over almost the entire duration of human habitation on Earth. Our biological hardware is fine, and indeed rather remarkable. However, the operating system we currently run in our brains, called modernity, has fundamental flaws that will self-terminate the enterprise via disregard for ecological and planetary limits. Humans are incredibly plastic and adaptable. A newborn does not yet have this operating system installed, meaning that enormous changes are possible under different material and cultural conditions.
I am not saying that a reversion to hunter-gatherer lifestyles comes next, even though we know that mode is well tested. We can try something new that might have elements of hunter-gatherer ways and modernity, while perhaps being unrecognizable to either. In any case, I am “doomerish” about modernity as a misguided enterprise and think we will need to face letting go of it. Recovering from overshoot is unlikely to be fun. My optimism lies in knowing that—after the dust settles—humans are capable of forming meaningful, respectful, and sustainable relationships within the community of life—founded on humility rather than hubris—as a part of nature, not apart from it.
Ben: Dave, I’m curious to what extent you agree with Tom’s assessment of modernity’s future, as a distinctive concept from humanity’s future?
Dave: What is modernity? We need to define further what we are discussing. Is insulin production part of modernity? Cancer medication? Vaccinations? Food production systems? Probably not the high-powered fossil-fuel variety of food systems, but what about agro-ecological food production systems that are organic but probably use some fuel in tractors, etc.? Are all technology and energy applications, aside from primitive tools, etc., out in this vision of the future?
If we are saying that all the advances of modern medicine and society that require, for example, plastic or energy must be abandoned after the “dust settles,” well then, I am not sure what to say. I feel as though it goes against human nature—not to mention unethical—to advocate for a future society that knowingly rejects the basic medicines and technology that are required for the survival of so many people.
Assuming we are not discussing that type of future, the question then becomes one of line-drawing. What is considered part of the “modernity” that must be rejected, and what is part of “modernity” that we will keep? Insulin production is a great example. Millions of people around the world require insulin to stay alive, and that insulin is (I assume, because I have not researched this) produced in fairly advanced facilities using a lot of new technology and energy resources. If we want to maintain insulin production in the future, we must maintain the supply systems for producing that insulin, which will also entail the requisite extraction of materials from Earth and energy consumption.
The production of insulin becomes one of minimizing impacts rather than eliminating them. The energy transition is the best way to minimize the impacts associated with energy production systems, so I advocate for it, acknowledging that there will still be impacts. The energy transition doesn’t “save the world,” but it has the potential to provide essential and non-essential goods and services with much lower impact. Why spurn that opportunity if we know we will need to continue to produce goods and services in the future?
Conspicuous consumption and much of our fossil-fuel-powered growth must change if we are going to have some sort of harmony with Mother Earth, but I think collapse is neither the best nor the only way to get there. Recent research shows that electrification alone, as part of the energy transition, will lead to a 40% decrease in global final energy demand due to more efficient end-use. That is a massive decrease in final energy demand, which translates to an even larger decrease in primary energy demand. And, as Amory Lovins wrote about this topic 40 years ago, people often overestimate the impact of the Jevons Paradox. People don’t do more laundry because they have purchased a more efficient washing machine. For sure, they may drive a bit more if their fuel costs go down due to a more efficient engine, but people who buy electric vehicles are not driving so much more that it actually increases energy consumption. I think it is a mistake to assume that the trends we see at the very beginning of the energy transition—i.e. that renewable energy has largely added to, rather than substituted for, other energy consumption—will continue in the future.
Ben: Tom, I wonder if you could offer a definition of modernity and say a little bit about what elements of modernity we might expect to retain in the long run?
Tom: Modernity is the dazzling and manifestly temporary fireworks show that we find ourselves living within, and to which we are wholly inured, so that we lack perspective on what might possibly be viable in the long term. Modernity, via rapid and grossly unsustainable expenditure of a one-time inheritance, puts humans so completely out of context as to render meaningless any artificial attempts to draw lines regarding what may or may not be part of the future. We only fool ourselves into thinking that we can play such a game, or that our ethical preferences have a say over what’s possible. We have far less agency than the recent windfall has led us to believe. The menu is not for us to decide, as we are embedded passengers within—rather than creators or masters of—the natural world, upon which we are utterly dependent. We have some agency, in that we could—in principle—decide to prioritize ecological concerns over modern expectations and live conservatively within the perceived limits.
Pursuing this further, we don’t arbitrate what is or is not sustainable, any more than we decide how strong gravity ought to be today. Since our true context is as an evolved biological species operating within a larger and exceedingly interdependent community of life, we must assume that the health of that broader community is vital to our long-term success—including the vitality of unknown species with which we share co-dependencies we will likely never understand. The present cocktail of ecological ignorance and destruction is akin to sawing off the branch on which we stand, enamoured of our power and technology to carry out such an operation.
Since 1970, the average decline in vertebrate species is about 70%. Wild land mammals—now comprising 2% of total terrestrial mammal mass compared to 96% in the form of humans and domesticated animals—have been eliminated to the point that only 2.5 kg of wild land mammal mass remains for each human on the planet. This was 80 kg per person in 1800, and 50,000 kg before civilization sprang up. They’re almost gone. A major disruption in global food supply—perhaps instigated by fossil fuel shortages—could essentially finish the job.
To reinforce an earlier point, these declines—similar in birds, amphibians, and insects—are not primarily due to CO2, but trace to the much longer pattern of modernity’s expansion and heavy use of energy and nature’s provisions.
In light of this, the prospect of maintaining insulin for human health is in doubt, as doing so requires some threshold in technology, mining, resource extraction, energy, pollution/waste, etc., that may be well over the line of what the community of life can accommodate in the fullness of time. Can we justify prioritizing insulin over ecological health, and is it even a valid choice in the end? If one nation had a long history of expansion, overrunning and displacing technologically inferior and peaceful nations to the point that complete elimination/dominance was in sight, is it justifiable to prioritize the healthcare of that nation’s citizens before trying to end the war against innocents? The question is even more poignant when the expanding race cannot itself survive if indeed managing to eliminate the “competition,” although few seem to be aware of this built-in peril of “success.”
So, I don’t think it’s within our power to decide how many of modernity’s perks we can keep. Ecological context comes first, which we ignore to our ultimate peril. We have zero evidence demonstrating long-term sustainability while enjoying modern conveniences like insulin, but ample evidence that the current system is woefully far over the line, by perhaps orders of magnitude. Any number of tweaks to a grossly unsustainable system—changing the energy source that drives the machine, for instance—are unlikely to alter its fundamental character or aims. It seems like too much to ask that modernity’s forward march will inexplicably, luckily, reverse course on ecological harm without its becoming the overriding, non-negotiable priority, based on the track record thus far.
Therefore, I would again guess that modernity, in its fundamental structure, is incompatible with planetary limits, and thus has no path to unsustainable continuance (an oxymoron, in any event). How much we must abandon is very hard to say, but I would be prepared to believe: most of it.
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.
Read the whole series: Part One | Part Two | Part Three | Part Four | Part Five






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This is an important discussion as it addresses how we should live now. If David’s approach is the one to follow (identify what aspects of modernity we wish to keep as we simplify), or Tom’s (understand and respect the biophysical limits we have no choice to operate within if we wish to survive), determines how we should live as a species.
Both approaches have merit and could be integrated. First identify what the biophysical limits are we need to operate within, then peal away those aspects of modernity that do not meet universal basic human needs (both physical and social). I suggest universal basic human needs as a basic goal for survival that we can enjoy. Additional “nice to haves” could be added if, but only if, those universal basic needs are first met for everyone. And there is reasonable doubt to think such “nice to haves” are feasible (but that’s another discussion).
Quantifying biophysical limits is critical, as is ensuring we keep an eye on measuring the cumulative human impact/drawdown of natural systems. The issue of population size cannot be ignored, as it’s a major contributor to total impact.
As Tom points out, we are in an advanced state of ecological overshoot, and the time line of approaching irreversible ecological tipping points is not encouraging. Simplifying how we live to focus on universal basic needs fast enough may not be possible. Without quantifying our limits we wont appreciate how urgent this task is. Even if our best possibly realistic outcome is some small bands of humans surviving “post growth”, that seems a worthy goal.
When Dave says "I feel as though it goes against human nature—not to mention unethical—to advocate for a future society that knowingly rejects the basic medicines and technology that are required for the survival of so many people" I don't think he has grasped the basic issue, which is that we don't get to decide those things. "Reality" will make those decisions for us – as it always has.
To Tom, with thanks. Thinking out loud….
https://www.researchgate.net/publication/401445532_An_Abundance_Trap_The_Perverse_Logic_of_Global_Collapse
This is almost too short to be useful; hopefully the Murphys continued from this opening statement context.
On saying it's unethical not to figure out how to keep providing insulin–I'm afraid such questions require a telescopic view. If you know someone with diabetes, that seems imperative. But in the long run, it simply will not be possible to maintain the highly complex systems that manufacture insulin, and CPAC machines and oxygen etc. We have to ask where we direct what surplus remains. Surely it would be unethical to abandon insulin production while continuing to fuel private jets. But it would also be unethical to prioritize it over helping healthy people move from places like the Middle East, that can't support them, to places that maybe can. Likely 8 billion is unsustainable, in which case the first to go could quite sensibly those whose survival depends on complex technology that isn't long for this world.
Diabetes comes in two varieties. Type II diabetes, formerly known as adult onset diabetes, will disappear all on its own once the lifestyle that causes it, a diet of junk food and a sedentary lifestyle, becomes impossible. The continuing concern would be type I which is genetic–and I think reality is that with this and other genetic defects, we need to return to the old-fashioned mechanism in which defects incompatible with survival were eliminated from the gene pool by death, or inability to procreate. Some of these are carried on many generations by being recessive and having carriers–and here is a place where modernity could be helpful. If you know there is one of these diseases in your family line, you could use IVF to have lab workers select embryos that are not affected and not carriers to be implanted in the mother, thus allowing your line to continue with the defect excised.
In the short to medium term, things will be painful, but in the long term we can have a healthy, flourishing humanity living in harmony within the web of life. How possible that is depends a lot on how long we insist on maintaining modernity with its destructive impacts on ecosystems.
I may have more to say after I read the rest of the article, but I disagree with Dave Murphy about washing machines. I'm certain that we do way way way more laundry than our great grandmothers did (in those days, men didn't do laundry). I'm sure that every shirt did not land in the hamper the minute it came off one's body. Men wore detachable collars so that the collar could be washed without washing the rest of the shirt. That's the origin of ties. People used to spot clean. I still do, but I think most people wash the whole garment.
It's true that there's a limit to how much laundry an individual might generate, but Jevons paradox extends beyond the specific activity that became more efficient. With the time NOT spent doing laundry (because the machine does it for us), we do all sorts of other things, most of which consume exergy.
I agree with Tom Murphy that we won't go directly to pure foraging. Not only do we not know how, we've so badly degraded the ecosystem that it won't support even as many foragers as it might have in the past. If collapse is extensive and sudden, that will mean death on an unbelievable scale, that we cannot prepare for. The best we can prepare for is some sort of middle ground that moves society in a lower energy direction, if we can do so without autocracy, conflict, and slavery. And that's a big IF.
The piece missing from this discussion is one of time frame. Over the long haul, T. M. is correct, that we humans don't get to decide. When a resource ceases to be humanly accessible, it exits the human economy, no matter how much we liked having it. Over the short to medium term, we still have options, which D. M. counts on.
We don't know how resource depletion on a planetary scale will play out, or whether enough humans will exhibit improbable bursts of wisdom to find ways to cushion the consumption descent. I like the way Nate Hagens frames the future as sets of plausible scenarios, where each scenario is composed of elements on axes that have varying degrees of interdependence. For example, an ecological space of degradation or regeneration has some dependence on a biophysical economic space of extraction and depletion, thus grouping certain ranges within each space into one scenario, but also have enough independence to be worth considering in their separate data spaces.
Using the scenario approach, modernity could crash off a single Seneca cliff, glide down a softer Hubbert slope, rachet down a series of Seneca cliffs, or behave something like a labyrinth. In a labyrinth, you sometimes have to move in what appears to be the wrong direction in order to get to a place where you can move more directly towards the target, which happens repeatedly. The same happens in my neighborhood, trying to get to the northbound freeway entrance, where I must go south, west, south, and east through local streets to get there.
For example, in the sustainability issue, I think ultimately we will create the equivalent of paleo trash pits for composting, where we may be able to harvest some amount of local biogas for cooking, to conserve forest. My local government has started a kitchen-scrap composting collection service, which some people who already compost object to because of the diesel consumption of the truck. But if this service gets people who wouldn't otherwise consider composting to segregate their compostables for pick-up, that may move us closer to a universal composting mindset that will eventually obviate the need for the diesel truck. This strikes me as a means of softening the consumption descent, using means that are still available to us, by traversing a labyrinth of switchbacks rather than crashing off a cliff.