The crowd gathers outside the shining glass towers, watching another ribbon-cutting ceremony for a new “smart city” development.
Solar panels glisten on the rooftops, electric buses hum along dedicated lanes, and politicians speak breathlessly about sustainable urbanisation.
The mayor unveils plans for another million residents by 2050.
Everyone applauds the vision.
Everyone except the mindful sceptic, who knows something about fossil fuel subsidies and the mathematics of feeding cities.
Core Idea
For the last 200 years, cities have grown exponentially on the simple premise that rural areas can be made to produce surplus food with minimal labour through fossil fuel subsidies.
Tractors, fertilisers, pesticides, processing plants, and refrigerated transport will all be powered by cheap energy, a subsidy to allow fewer farmers to feed more city dwellers on an unprecedented scale.
And it worked.
The UN projects that by 2050, 68% of humanity will live in cities. That’s 6.7 billion people fed by 1.8 billion rural residents, which is 300 million fewer than today’s rural population.
The arithmetic is staggering… fewer people on the land must produce 25% more food to feed urban populations that will grow by nearly 50%.
This projection makes one huge assumption. It implies that the exogenous energy from the fossil fuel pulse that makes intensive agriculture possible will continue indefinitely.
It won’t.
Counterpoint
The dominant narrative treats urbanisation as natural law.
Rural life is hard labour for little reward. And while technology makes farming more efficient, cities are where opportunities happen.
And, of course, smart cities will solve sustainability challenges.
This is progress, and progress is irreversible.
But urbanisation is not progress—it’s dependency. Every city dweller relies on an invisible army of fossil fuel slaves working the fields.
A single barrel of oil delivers power equivalent to 2,500 hours of human labour. Remove that subsidy, and the mathematics change completely.
The energy return on investment (EROI) for industrial agriculture is negative. More energy in than out. It takes roughly eight units of energy input to deliver one unit of food energy to urban consumers.
This works only as long as energy is abundant and cheap. When fossil fuels become expensive or unavailable, the system breaks.
What happens when the subsidy fails?
Cities cannot feed themselves. The alternative food production systems will necessarily be more labour-intensive, local, and circular. More people will need to grow food. Not by choice, but by necessity.
History offers a preview.
Before the fossil fuel pulse, over 90% of humans lived on the land. After fossil fuels peak or are phased out for climate reasons, the percentages will shift back. Not to medieval levels, but significantly more than the UN’s projections assume.
Even the smart city vision collapses when you follow the energy flows.
Vertical farms require 30 times more energy than field agriculture. Urban food forests cannot feed millions. Supply chains spanning continents depend on cheap transport fuels that may no longer be cheap.
I think you get the idea.
Thought Challenge
Take your city’s sustainability plan and trace the food sources... Calculate the land area required to feed the population locally. Then ask yourself what would happen if diesel cost $10 per litre?
Map your own food dependency... For one week, note where everything you eat comes from. Calculate the transport distances and energy inputs. Then ask yourself, what would I eat if nothing travelled more than 100 kilometres to reach me?
Closing Reflection
The mindful sceptic sees through the urbanisation orthodoxy to its hidden assumptions.
Cities are not sustainable; they are subsidised. The subsidy is ending, whether through resource depletion, climate action, or economic collapse. When it does, the great urban experiment will reverse, not by ideology but by thermodynamics.
This is not catastrophism but accounting.
People will return to the land not because it’s romantic but because it’s necessary. The only question is whether this transition happens by design or disaster.
Smart cities are not the future. They are the last gasp of an energy-abundant age. The real intelligence lies in preparing for what comes after.
And should the techno-optimists come at you with the ‘what about fusion’ argument, tell them that kicking cans down the street is noisy and hurts your feet.
Evidence Support
Ayres, R. U. (1998). Eco-thermodynamics: economics and the second law. Ecological Economics, 26(2), 189-209.
TL;DR… how thermodynamic laws, especially the second law, constrain material and energy use and impose limits on economic systems. The paper argues that conventional economic models neglect these constraints, leading to unsustainable resource use.
Relevance to insight… foundational in connecting physical limits of energy and matter with unsustainable development, directly supporting the insight that sustainability is fundamentally constrained by thermodynamics and ecological realities.
Georgescu-Roegen, N. (1971). The Entropy Law and the Economic Process. Harvard University Press.
TL;DR… economic processes inevitably increase entropy, making indefinite material growth impossible. His analysis demonstrates that all resource use leads to unavoidable degradation and decline in environmental quality.
Relevance to insight… clear theoretical reasoning for why economic development cannot be truly sustainable in a finite system, matching the insight’s premise.
Hall, C. A. S., & Klitgaard, K. A. (2012). Energy and the Wealth of Nations: Understanding the Biophysical Economy. Springer.
TL;DR… economic growth relies on energy availability and how declining energy return on investment (EROI) leads to systemic vulnerability. Their empirical research shows that modern economies are exceptionally fragile as they breach energy and material limits.
Relevance to insight… theoretical and data-driven evidence that sustainable development claims must be reconciled with the declining supply of net usable energy, supporting the thermodynamics constraint highlighted in the insight.
Daly, H. E., & Farley, J. (2003). Ecological Economics: Principles and Applications. Island Press.
TL;DR… how economic and environmental processes are intertwined and subjected to biophysical boundaries. The authors reveal that economic activity exceeding ecological carrying capacity causes irreversible damage and system collapse.
Relevance to insight… sustainability in economic systems is not a matter of efficiency or technology alone but is limited by critical ecological and thermodynamic thresholds.