One of the looming subjects when it comes to the question of “feeding the world without destroying the planet” is population. It’s definitely among the most uncomfortable aspects of the discussion, as there are some tremendous examples of bad answers, and few good ones. “We have too many people” on earth is the typical perspective, tho most recently there is strong concern about massively dropping birthrates around the globe. Either way, when we look at the numbers it’s quite staggering. The rate of population growth peaked in the 1960s globally, but we’ve still gone from 2 billion people in 1927 to 8.2 billion 100 years later—a full quadrupling of population in a couple generations. Every single person needs some 2500 calories a day. A century ago we needed baseline supply of 5 trillion calories a day, and now it’s at 20 trillion.
What does this mean practically?
First, our population affects every single ecosystem, in ways we never have previously (I wrote about major ecosystem change by the first peoples of every continent in my last article on global carrying capacity). This fact alone makes us a keystone species, as our collective behavior affects the function and habitat of every other species on the planet. Shipping, packaging, manufacturing, energy production plays a massive role in this impact—for instance there is plastic trash at the top of mount Everest and in the Mariana Trench. That being said, nothing affects land, water, and biodiversity as much as our food systems do.
Second, there is no wilderness anymore. It has been centuries since maps left out entire parts of the globe with “here be dragons” as a warning against human encroachment (and that doesn’t count all the indigenous folks who didn’t make maps in the conventional way we think of them). Today, satellite data can track individual trees from space; within one generation we will be nature’s panopticon.
Third, there is no “away” anymore. We cannot discard anything en masse without affecting both people and planet. With a smaller population, externalities were less acute, and their impacts were easier to ignore.
Fourth, there are two frontiers left: The ocean, and space.
The demographer’s of our time anticipate that human population will level off at between 10 and 12 billion humans in the coming two generations, though there is some concern about demographic winters on one end, and overpopulation leading to collapse on the other (which is usually described as overconsumption rather than overpopulation).
This brings us back to the rabbits & foxes graph, which i used in discussing cycles of degradation in a previous post. Although, we could also consider it the Deer & Denudation graph—substitute any predator and prey, or any herbivore and groundcover for the red and blue lines in the graph below. It’s not hard to zoom in and make it match the graph above, and this is what many folks think — we’re hitting the steep part of the graph, consuming that which we depend on, which will lead to a precipitous drop. That’s Malthusianism in a nutshell, but it’s also too simplified, even if it’s based in science. What we really need to understand when talking about demography is density dependence.

Density dependence in population ecology refers to how population growth rates change as population density increases or decreases. When a population is density-dependent, vital rates like birth, death, and migration are influenced by how crowded the population is. Humans are density dependent in some really key ways:
Disease transmission increases and happens more rapidly in crowded conditions, from historical plagues in dense cities to modern COVID-19 outbreaks. Higher population density increases contact rates and transmission pathways.
Resource competition becomes more intense with density. While we are amazing at increasing resource production, local competition for resources like housing and services intensifies in dense areas. This in turns affects birth rates, as people delay reproduction due to higher competition and higher inequality.
Social stress and mental health often worsen with overcrowding. High-density living can increase psychological stress, violence, and social pathologies, potentially affecting both mortality and reproductive decisions. This manifests in multiple ways, but as a general rule, crime is higher in dense urban locations than in sparse ones.
Infrastructure strain in dense populations can overwhelm sanitation, healthcare, and food distribution systems, leading to higher mortality rates during crises.
BUT humans are also density independent:
Technological innovation allows us to increase carrying capacity (at least temporarily). Agricultural advances, medicine, and engineering help populations grow—and this runs the gamut from women being able to freeze eggs and hire a surrogate, functionally extending the possibility of childbirth into menopause—to genetically modifying agricultural crops to increase food production — to medical advances extending lifetimes.
Global trade networks mean local populations aren't constrained by local resources. Dense urban areas can import food, water, and materials from vast distances.
Cultural adaptation enables humans to modify behavior and social structures to handle density changes, from urban planning to social institutions.
Medical advances have largely decoupled human mortality from many density-dependent factors that historically limited populations.
This mixed pattern makes human population dynamics uniquely complex - we show characteristics of both density dependence and density independence. This complexity is magnified by the fact that we have no predators, which are nature’s preferred method of population control and equilibrium. Nature’s other favorite method is disease or blight, which we actively combat through technology and medical advances.
A recent article in the Atlantic, written by Marc Novicoff, suggests that “ humanity is shrinking several decades ahead of schedule” and that our overall population will start declining within my lifetime (if I live to 90 i’m only halfway done), and that this presents enormous challenges from a socio-economic-political perspective:
Falling birth rates create cascading effects across multiple dimensions of society, fundamentally reshaping economic structures, political dynamics, and social contracts that have defined modern civilization.
Economic Implications of falling populations
Labor Market TransformationL Shrinking workforces lead to labor shortages in key sectors, particularly healthcare, education, and skilled trades. This creates wage inflation as employers compete for fewer workers, while simultaneously reducing overall economic productivity. Countries like Japan and South Korea are already experiencing severe labor constraints that limit economic growth potential, while putting enormous pressure on the young.
Fiscal Crisis and Debt Sustainability The mathematics of pay-as-you-go pension systems become unsustainable when fewer workers support each retiree. Germany's ratio of workers to retirees has dropped from 6:1 in 1960 to roughly 2:1 today. This demographic inversion forces governments to choose among raising taxes on a shrinking workforce, cutting benefits, or accumulating unsustainable debt levels. Healthcare costs compound this problem as aging populations require more intensive medical care. There are more draconian options suggested in all kinds of science-fiction or dystopian novels, none of which are palatable in free societies.
GDP and Economic Growth Economic growth traditionally depends on expanding labor forces and productivity gains. With declining birth rates, countries face "secular stagnation" - persistently low growth rates despite monetary stimulus. Consumer markets shrink as populations age, reducing demand for housing, education, and consumer goods while increasing demand for healthcare and eldercare services.
From an ecological perspective, all these dynamics may have a silver lining to the clouds, in the sense that pressures on planetary limits are reduced as populations go down, but I’m not convinced that’s actually the case. As countries increase in debt, increase in a need to care for elderly, and cannot rely on sufficient numbers of workers to make ends meet nationally, I anticipate that the temptation to exchange ecological capital for short-term financial gain would actually increase, though whether or not this would be balanced by a reduction in aggregate demand is an open question.
Social and Care Infrastructure
Eldercare Crisis The "sandwich generation" phenomenon intensifies as smaller cohorts of working-age adults must support both their children and aging parents. Traditional family-based eldercare systems break down, forcing expensive institutional solutions. Rural communities face particular challenges as young people migrate to cities, leaving elderly populations with limited support networks. For example, the one child policy of China created a dynamic in which one child becomes responsible for caring for two parents, and 4 grandparents, putting enormous pressure on the young, and putting significant economic hardship on prospects for raising children.
Healthcare System Strain Aging populations require more frequent and intensive medical interventions, creating bottlenecks in healthcare delivery. The ratio of healthcare workers to patients deteriorates, while training new medical professionals takes years. This creates a feedback loop where healthcare becomes more expensive and less accessible.
Political and Security Implications
Democratic Representation Aging populations tend to vote more conservatively and prioritize different policy issues than younger cohorts. This can create political gridlock around necessary reforms, particularly those requiring short-term sacrifices for long-term benefits. Intergenerational conflict emerges as younger voters feel their interests are systematically underrepresented.
Military and National Security Smaller populations mean fewer potential military recruits, forcing nations to rely more heavily on technology, professional military forces, or alliances. Countries like Russia and China face particular challenges maintaining large military forces while their working-age populations decline. This can alter regional power balances and security arrangements.
Immigration and Cultural Dynamics
Immigration as Economic Necessity Countries with below-replacement fertility rates increasingly depend on immigration to maintain economic growth and support aging populations. This creates tension between economic necessity and cultural identity concerns. Even traditionally homogeneous societies like Japan are reconsidering immigration policies out of demographic desperation.
Cultural Integration Challenges Rapid demographic change through immigration can create social friction, particularly in communities unprepared for cultural diversity. Political movements exploiting these tensions have gained influence across Europe and North America. The success of integration depends heavily on economic opportunities, institutional capacity, and social cohesion.
Urban-Rural Divides Immigration often concentrates in urban areas while rural regions continue aging and depopulating. This geographic sorting reinforces political polarization and can undermine national unity. Rural areas may become increasingly dependent on urban economic centers while feeling culturally alienated from them.
Is population a catch-22?
The question of population may seem to put us in a Catch-22. Sharply falling birthrates present enormous challenges to societies, even though they may reduce pressure on ecological boundaries for human society. Population growth, on the other hand, follows the same pattern we’ve seen historically, where eventually we hit ecological limits through the consumption of soil and water. The largest factor in growth rates falling below replacement levels appears to be the education of women and girls, which in every other aspect is a massively positive development over the last couple centuries.
Technology has a huge role to play in the adaptation to these — advances in robotics and AI are already starting to replace labor in all kinds of situations where traditionally the elderly have depended on the young.
Policy adaptations that glowing the rate of population decline may be the difference between demographically pumping the brakes and slamming into a wall, though it’s questionable what policies work at doing that. There’s a limit to the extent that policies create incentives and incentives drive behavior — yes we definitely respond to incentives, but we also respond to status signals and societal changes(which policy takes a longer time to affect).
Here’s the thing tho, regardless of what population does, it does not affect what our objectives on the supply-side of ecological capital should be. If population is the main driver of demand for aggregate consumption of nature, that deserves its own set of policies and actions we take, but how we manage land and natural capital is the demand-side.
So here’s what I suggest:
On population we should pursue policies, incentives, and actions that avoid following the typical predator-prey pattern as much as possible. This is a well-established pattern that’s been observed in all kinds of populations in nature, and it’s quite terrifying. That precipitous drop illustrates the functional equivalent of driving a car into a wall at full-speed. If we can manage a population decline at slower rates, it will alleviate the severity of the challenges discussed above, and we should use whatever tools at our disposal to demographically pump the brakes rather than slam into the wall. At some stage we will hit a new equilibrium, until technology and resource use and policies and culture affects us enough to change course. Doing that without resorting to draconian or authoritarian policies is paramount, as we can see that the authoritarian and draconian attempts at population control to date have been disastrous on both individual and societal levels.
But what about on the demand side, as it relates to natural limits, resource use, soil, water, and biodiversity? On that, our goal should be the same, regardless of what population does: Maximize the carrying capacity of earth. In my last post I noted the importance of concepts like Rockstrom’s planetary limits and Raworth’s donut economics, and noted that these narratives haven’t emphasized that earth’s carrying capacity is actually determined by our aggregate decisions in how we manage land, water, soil, and biodiversity.
To reiterate, the fundamental meaning behind humans as a keystone species is that every other species and all ecosystems are affected by the decisions we make. We, homo sapiens, are what determine the ultimate carrying capacity of earth, and we can shrink or magnify earth’s carrying capacity, depending on how we manage it, within the parameters of macropatterns that maintain earth’s natural systems.
Thus, on the supply side of demand for nature, we have population dynamics, with their assorted challenges whether we are growing or shrinking as a population, but on the supply side, regardless of what population is doing, our objective should be to maximize the carrying capacity of earth. That ultimately will determine what stabilizes our population, and will put us in a position to limit the amount of degradation we impose on our home’s life-support systems.
Excellent analysis, Neal. You mention AI replacing labor, and I'd be curious to see your complex system analysis extended to further include this dynamic. Especially the massive and rapidly growing depletion of ecological capital in the form of mineral mining, energy consumption, and water use and contamination caused by AI and data centers. Included in this added complexity would be something like Jevon's paradox, where cost savings involved in AI replacement of labor seems to mean that the technosphere will expand ever more rapidly. Economic costs decreasing leading to increasing ecological and hydrological costs. Thanks again for sharing your insights. I much appreciate how you apply your mind and communication to systems in dire need of it. Cheers.
A good analysis, but one place I'd disagree with you is the inherent assumption that the number of productive people required to care for each non-productive person is constant. Increased automation - especially AI - will shed jobs, at the same time as we need more people in the care professions - so we'll see a shift in the kinds of employment towards the things humans do better than machines.
The area this breaks down is the "economic" side of caring - this fails if all the wealth from reduced requirements for labor ends up in the hands of oligarchs rather than being distributed. This, of course, is part of the doughnut economics way of looking at things.