22 | Joe Walston on Conservation, Urbanization, and the Way We Live on Earth
What this covers
Sean Carroll speaks with Joe Walston, a wildlife conservationist with fifteen years of field experience across Africa and Southeast Asia, about an unexpected path toward stabilizing human population and enabling nature's recovery. The conversation centers on urbanization as a paradoxical force: rather than a symptom of ecological collapse, cities drive the demographic transition that lowers fertility rates, raises female empowerment, and reduces per-capita resource consumption. Walston argues that the critical window lies in the next fifty years—a developmental bottleneck in which the fate of key species and forests will determine whether nature can recover or decline irreversibly.
The discussion moves through the mechanics of how urbanization works as a conservation engine. Walston traces the demographic transition not primarily to healthcare or education, but to urbanization itself, which bundles access to opportunity, lower child mortality, and social mobility. He examines marginal consumption of nature, showing how most resource extraction occurs during the escape from extreme poverty, not as wealth continues to climb. A critical claim: the urban middle class has historically been the sole driver of environmental advocacy, from nineteenth-century London to contemporary India. He contrasts this against the scale of human spatial footprint—cities occupy roughly five percent of Earth's land surface even as population reaches eight billion, leaving potential space for both human settlement and nature's renewal.
The conversation addresses contentious terrain: whether restricting immigration might increase global population pressures, how the brown-to-green transition from anti-pollution movements to nature protection unfolds in developing economies, and whether the foundations for actual nature recovery are truly being laid. Walston presents data on extreme poverty reduction, resource use density in cities, and the historical record of species recovery where it has succeeded, while acknowledging that catastrophic loss—like the passenger pigeon—remains possible.
Walston argues that urbanization, rather than being an emblem of uncontrolled human expansion, is the single greatest driver toward stabilizing the world's population and lifting people out of poverty, and that getting nature through a 50-year 'bottleneck' now could enable not just slowing decline but an actual recovery of nature.
- Urbanization drives the demographic transition that lowers fertility, raises female empowerment, and reduces per-capita resource consumption
- Cities generate the urban middle classes who become the advocates for nature, as historically happened in London and New York
- The next 50 years are a decisive 'bottleneck' in which conserving key species and forests determines whether a renaissance of nature is possible
Urbanization is the single greatest driver of fertility decline and population stabilization worldwide.
- Population growth is not a smooth compound-interest story; for most of history births only slightly exceeded deaths, and the modern population spike resulted because social and medical change (penicillin, germ theory) drove the death rate down long before the fertility rate fell, opening a gap that produced the spike.
“The change that happened in society drove the death rate down long before it drove the fertility rate down. And that's what led to this absolute spike in the population growth rate.”
- When governments give people both the choice to move and the ability to take advantage of that choice, people consistently urbanize; this was demonstrated when Deng Xiaoping's post-Tiananmen reforms freed Chinese mobility and people flocked to coastal cities, and when forcibly displaced populations elsewhere move once restrictions are relaxed.
“it's actually just looking across what happens when people, A, have the choice and B, most importantly, or as importantly, have the ability to take advantage of that choice. It's all very well to have a choice, but if you can't afford to move, or if there are other things keeping you there, then it's worthless.”
- Contrary to the common perception that cities are the exemplar of an uncontrolled human population, cities are actually the greatest drivers of bringing about stabilization of the world's population.
“people need to be really aware that cities are the greatest drivers of bringing about a stabilization of the world's population... often people see almost cities as the exemplar of an uncontrolled human population, and that's actually the reverse.”
- The demographic transition proceeds in stages: first, high mortality and high birth rates roughly balance; second, basic interventions (disease control, fresh water, sanitation) drop mortality while fertility stays high (10-12 children), causing populations to spike; third, fertility falls as people choose to invest more in fewer children once they have confidence those children will survive.
“The mortality rate goes down, the fertility rate stays the same, and therefore populations start to go through the roof. And then of course, the third phase, which is that those same communities, those same societies then respond, and the natural fertility rate comes down.”
- Although many attribute falling fertility to healthcare, education, or general wealth, the most underestimated and near-ubiquitous driver is urbanization itself: cities provide greater access to education, sanitation, lower child mortality, and social mobility, and many factors people treat as causes of lower fertility are actually consequences of urbanization.
“whilst some attempts were very culturally specific... what the overriding influence, or a huge influence, underestimated influence, is purely the nature of urbanization.”
- The romantic image of bucolic countryside versus filthy slums inverts reality: on metrics from child mortality to abuse to women's rights, conditions are much worse for the poor and for women in rural areas than even in low-income urban slums, which is why people choose to move to cities.
“the stats on everything from child mortality, to abuse, to women's rights, they're much worse in in these areas than cities, even sometimes these low income slum areas.”
- Despite widespread panic over China's one-child policy and its revocation, the policy's demographic effect has been utterly overwhelmed by the far larger forces of urbanization and wealth creation.
“everyone panicked about the one-child policy and the revocation of that in China. It's been utterly overwhelmed... by the process of urbanization and wealth creation.”
Urban middle classes are the decisive force for environmental protection and positive social change globally.
- The urban middle classes are almost invariably the single greatest drivers of positive social change worldwide, and crucially the environmental movement has never been a rural movement but has consistently emerged from wealthy and middle-class urbanites in big cities.
“The urban middle classes are almost invariably across the world the single greatest drivers for good, for social change in countries... ultimately where the environmental movement comes from, we should always never forget, they're not rural movements.”
- Environmental movements emerge through a predictable transition: people move to cities and create wealth but suffer from pollution (the 'brown' environment); those who benefited then advocate against that pollution, and as the movement grows it spreads 'up into the green,' demanding nature protection.
“All the environmental movements came actually from the brown... What we call a brown environment, which is pollution... And then those same people that benefited are now suffering from that, started advocating for better environmental conditions. And as that grew out, so it spread up into the green and demanding nature”
- In a world where people are educated, urbanized, and connected, they will make far better environmental decisions and be far better conservationists than in the past, whether they live in downtown Manhattan or on a mountain in Montana; urban people are much more likely to vote with environmental issues in mind and to found sustainability movements.
“in a world where people are educated, urbanized, connected and in that, they are going to be making far better decisions and far better decisions on the consumption and the nature of impacts of this world”
- Returning to Bangalore 20 years after finding only depressing remnant pockets of wildlife surrounded by poverty, Walston found the city had become one of the largest markets for Nikon zoom lenses because the new urban middle class now visit, pay for, advocate for, and vote for nature, forcing conservationists to double their tiger-population ambitions.
“Nikon, one of the largest markets for Nikon Zoom lenses had become Bangalore. Why? Because these wealthy middle class... were now taking these cameras and going back out to these places where I had been 25 years ago and now they were the ones that are paying for, advocating for, voting for nature.”
- The idea that valuing and protecting nature is merely a Western luxury has been demonstrably disproven, as culture after culture now values its own nature and citizens of developing nations are increasingly demanding and acting to protect their own wildlife, such as Rwandans wanting their mountain gorillas.
“the idea that somehow these were just Western luxuries of us now has been proven demonstrably wrong, as culture after culture is starting now to value its own nature, appreciate it, and for the first time to be able, in many ways, to be able to put their hand up and say, 'No, I want,' whether it be Rwandans, 'I want my mountain gorillas in Rwanda.'”
- The greatest draw-down on nature comes not from the middle classes moving to upper classes but from people moving out of extreme poverty, because a person in extreme poverty spends almost an entire additional dollar on natural resources (food), whereas a wealthier person spends a far smaller proportion of an additional dollar on natural resources.
“when is the greatest draw-down on nature? Is it by me, in the middle classes moving up to the upper classes? No. It's obviously, actually, it's a movement of people out of extreme poverty”
Extreme poverty has declined dramatically and nearly universally across regions, lifting billions out of destitution.
- While inequality concerns are valid and the capture of wealth by the top 0.1% has been unprecedented, the worst case—people getting richer and poorer simultaneously—is not happening; in absolute terms the poor are getting less poor, with hundreds of millions to billions lifted out of extreme poverty, primarily in China and East/Southeast Asia.
“If one looks at inequality as literally how many people... The worst case surely would be people getting richer and people getting poorer at the same time... And that's not happening. That's really not happening.”
- However one measures extreme poverty (at $1, $1.50, or $2 a day), the global drop-off is extreme and ubiquitous across regions, and what was once considered a joke—eradicating extreme poverty—is now a revised, attainable Sustainable Development Goal after the prior goal of halving poverty was achieved.
“just look how incredibly steep that drop-off is, however you measure it... However you measure it, the drop-off is extreme and how ubiquitous it is.”
- Contrary to popular awareness, poverty levels in Sub-Saharan Africa are going down considerably and are predicted to continue falling even as the population continues to rise, as the region approaches the second phase of its demographic transition.
“The poverty levels in Sub-Saharan Africa, against many people's awareness, are actually going down quite considerably and fantastically, and they're gonna continue to go down, even though the population is going to go up.”
- China has been responsible for the greatest number of people moving out of poverty in human history over the last 30 years, an achievement that would have been very hard to imagine in an agrarian society; the government's key smart decision was not detailed planning but allowing people greater volition to move.
“China, which has been the sole responsibility for the greatest number of people moving out of poverty in the history of mankind, in the last 30 years. It is very hard to imagine how that could have possibly been done in an agrarian society.”
Development necessarily depletes natural capital, but this toll can be managed, sped, or lessened through policy.
- There is no society that has driven itself out of poverty without converting natural capital to economic capital, so there is an unavoidable toll on nature in development, though the impact can be ameliorated, sped up, or lessened.
“There isn't a society out there that hasn't through some form converted natural capital to economic capital in driving their economy out of a position of poverty.”
- How much of a country's natural estate survives its development depends partly on the speed of the urbanization-and-wealth transition and on having people who care enough to hold onto land; England developed slowly and destroyed most of its nature, the US developed faster but preserved large chunks, and China is developing fastest of all.
“what America managed to do is get much more of its natural estate through that bottleneck process... and it came out of the other end with large chunks of nature left into it. And that's partly, yes, you're a big country, but also the speed of that process happened”
- Nature is declining at terrifying rates and there is no inevitability to recovery; countries like Nigeria could pass through their developmental bottleneck over coming generations and emerge with no nature left, so conservation is a race to get as much nature through the bottleneck before destruction completes.
“there is no inevitability about what I've described... there is quite the possibility that countries like Nigeria, who go through its developmental bottleneck, as we describe it in the paper, over the next generations and come out with no nature at the end of it.”
- Conserving the world's remaining large intact forests is a prerequisite for meeting global climate change targets; if the Congo Basin is lost as it goes through its demographic shift, that affects every person in the world and the global ability to address climate change, regardless of technological strategies.
“if we lose the rest of the large intact forests of the world over the next 50 years, there ain't no way we're gonna hit our global climate change target... conserving these forests are the prerequisite to all the other strategies working in these areas.”
Nature recovery is achievable and beginning now, contingent on species and forests surviving the developmental bottleneck.
- For the entire history of the modern environmental movement, nature has been in steady decline and conservation has only ever managed to slow that decline; but just as we approach the crux of decisions on nature's future, we are beginning to establish the foundations for a real recovery of nature that is within our grasp in our lifetime or our children's, though it is not inevitable and could still be missed.
“all of conservation has been designed around merely slowing declines and we really haven't seen any sort of indication of anything but that continuation. But just as we are really getting towards the real crux on the future of nature... we're starting actually to see the ground work for establishing the foundations for a real recovery of nature.”
- Rather than human population growing exponentially until human biomass exceeds the mass of the Earth, we may be undergoing a phase transition to a new equilibrium with far more people but concentrated in urban environments, allowing a great deal of nature to be sustained and even recover.
“I think it's about 5%. I think it's likely to get up to 7% maybe in the next few years”
- The defining moment for nature is the next 50 years—not the 1800s or 1950s—because countries like India are now past the point of losing their iconic species (Walston guarantees India will not lose the tiger), a guarantee that would have been impossible 50 years ago.
“we have this terrifyingly exciting time over the next 50 years of actually this is the defining moment for nature. This 50 years, not 1800s, not even 1950. It's now.”
- If we succeed in getting iconic species and key forests through the developmental bottleneck, they will not merely survive in 100 years but become the source sites for a renaissance of nature, funded and advocated for by the peoples of those countries—just as the American bison recovered from a few hundred to hundreds of thousands while the passenger pigeon was lost forever.
“If we are successful at getting these areas and species through this bottleneck, they are then not only gonna be just there in 100 years time, they're gonna start coming back... they're gonna be the source site for a renaissance of nature”
Cities concentrate population on small land area, enabling both resource efficiency and vast land for nature recovery.
- Urban environments currently cover roughly 5% of the Earth's land surface, likely rising to about 7% in coming years, so even a future where 10-20% of land hosts most of the population could be a stable equilibrium leaving 80% for nature recovery and agriculture.
“I think it's about 5%. I think it's likely to get up to 7% maybe in the next few years”
- For equal wealth, people in dense urban environments use far fewer resources than suburban dwellers; the average New Yorker uses 74% less water, 35% less electricity, and 45% less municipal solid waste per capita than the average American—not because they are morally superior but because of how density works.
“for the average New Yorker per capita versus the average American, the New Yorker uses 74% less water consumption, they use 35% less electricity, they use 45% less municipal solid waste, I.e, garbage, per person per week.”
Humans are fundamentally alike and behave similarly under similar conditions across all regions and cultures.
- Contrary to the common belief that each culture is uniquely different, demographic and developmental trends are strikingly similar across China, Sub-Saharan Africa, and Latin America, demonstrating that humans are far more alike than different and behave similarly under similar conditions.
“wherever you are in the world, the commonality between these trends. What's happening in China, what's happening in Sub-Saharan Africa, what's happening in Latin America, are incredibly similar, and actually we are a lot more similar than we are different.”
- Rwanda, despite monumental setbacks and lacking the natural resources of Botswana or South Africa, has restructured and moved ahead of the curve through the demographic transition with a highly dense population, refuting the argument that there are circumstances making Africa fundamentally different.
“Rwanda really is a fantastic example of a country that has faced monumental challenges and setbacks and yet with a highly dense human population, it has managed to restructure and work itself through this transition.”
- For most of human history humans lived in relative population stability constrained by very high death rates, and the human distribution across all habitats and parts of the world has been a more impressive movement than the actual population increase, which is novel only very recently.
“for me, the distribution across all habitats and parts of the world has been a more impressive movement of people than has the actual population increase.”
- The Anthropocene is a valid description of a planet that is no longer defined primarily by geological or climate features but is singly defined by the human population and its impact on the Earth.
“Anthropocene is the word, which I think has merit and holds up as a description of a planet, which is defined no longer necessarily by purely geological or even climate features, but actually is singly defined by the population of humans and their impact on the earth.”
City-states and subnational entities now address global issues independently, replacing federal governments as primary influence.
- Because major cities are wealthier and more influential than most nations, linking them (e.g., New York to Lagos) to help with transport, water, municipal supplies, and waste would make poorer cities more livable and have enormous broader influence, exemplified by Bloomberg's C40 cities climate initiative.
“these cities, which are wealthier than most nations, which are certainly more influential than most nations, can link up. Imagine what we can do linking New York to Lagos or one of these areas. And literally, help with the things... With transport, with water, with municipal supplies, with waste and garbage”
- City-states, which disappeared after Renaissance Italy, are reappearing as cities and subnational entities like California, New York City, and Shanghai take up global issues such as climate change—sometimes disregarding national-level positions—making cities the way of the future in terms of influence rather than federal governments.
“we start to see cities, city-states reappear. Now, they disappeared in Renaissance Italy, they're reappearing now, with California as a state starting to make global climate change decisions. We're seeing New York City taking up and disregarding, really, what is happening at the larger, national level.”
- If the world could make African cities function the way New York, Shanghai, or Kigali do, it would have an enormous positive impact across a whole range of factors, requiring everything from basic municipal infrastructure (water, sanitation, transport, housing) up to a demanding, voting civil society.
“if you could make African cities work and function in the way that my adopted city New York or Shanghai or many of the other cities or some positive African city examples already can do, in places like Kigali... that will have an enormous impact on a whole range of factors.”
- Humans' defining ability is to store and share information, and cities are extraordinary engines of 'ideation'—the sharing and generation of ideas—which is central to the pace of human development; the internet and increased global connectivity are blurring with cities to extend this same idea-sharing function more globally.
“we call it ideation. The ability to share, it is a fundamental feature of humans. The reason why we have either made so much progress... is because we learnt how both to store information and to be able to share information”
Conservationists should expand options for rural populations including migration assistance rather than imposing paternalistic development models.
- Rural-to-urban migration is predominantly driven by youth seeking jobs and social mobility, leaving aging, dwindling remnant populations in rural areas, as observed in the depopulating Russia-China border region where tigers are conserved.
“the youth are moving away and you've got these rather, and frankly, rather sad populations up here of just remnant... People who are... They're just going to age out of the population. But youth move for, obviously, access to jobs, the ability for social mobility”
- Conservation organizations have traditionally helped poor rural people improve their immediate circumstances in place (e.g., chicken or fish farming), but it is no longer clear this is the best help; instead, organizations should give people more options—potentially including help to move—and trust that people know what is best for themselves rather than imposing an institutional imperative.
“Our tradition has always been to immediately help them with their circumstances, there and then... It's no longer clear that's the best thing to actually help people with. And we have to really rethink this as a conservation organization.”
- Developing regions can leapfrog whole generations of obsolete technology, as Africa did when cellphones jumped over fixed-line systems, and Africa remains at the forefront of using technologies in social ways from which others can learn.
“they have the chance, many ways to leapfrog whole generations of things that are no longer useful. When I was living in Africa, cellphones came and completely jumped fixed line systems in many parts.”
- The future world we should explicitly aim for rests on three foundations: a stabilized human population (the absolute number mattering less than that it stabilizes), the elimination of poverty (both a moral and a livability imperative), and a connected world that preserves cultural diversity while enabling shared values and global decision-making on shared issues.
“having a stable human population really is a goal that we should be looking for... let's face it, we should have no poverty... And then the third one... We need this connected world.”
- It is entirely possible to stabilize the world at 12 billion people, urbanized, connected, and out of extreme poverty, and yet still destroy nature, so achieving population and poverty goals does not guarantee preservation of nature.
“There's no reason why we can't stabilize the world at 12 billion people, have people probably urbanized, have people connected, out of extreme poverty, and yet there's very, very little of nature left.”
- Climate change is the biggest issue facing the planet today and an immediate, imminent worry, not merely a long-term one.
“climate change is the biggest issue facing our planet today.”
- Mathematics training was interesting but it is easy to overstate how much it truly helps in conservation work.
“It's easy to overstate how much it actually does truly help me in this. But occasionally, it's useful to say so.”
Meat consumption rises sharply at poverty transition, then plateaus; wealthier populations increasingly choose less meat.
- For individuals facing large global issues like climate change, eating less meat (not necessarily full vegetarianism) is a phenomenally high-leverage action because it simultaneously serves ethical, health, and environmental goals, with quantifiable impacts on water consumption and forest preservation.
“If you wanna really make an impact, just eat less meat... a wonderful confluence of, by taking a few common actions which aren't actually that big, one can have impacts on all three of those.”
- The biggest driver of Amazon deforestation is not palm oil but, by an order of magnitude, feeding the beef industry (including soy grown for cattle feed and dairy), and nothing comes close to beef on an order of magnitude for water consumption and forest loss.
“the biggest driver of deforestation in the Amazon is not palm oil; by an order of magnitude it is feeding the beef industry.”
- Meat consumption rises sharply at the transition out of poverty (when people can finally afford meat) rather than scaling with continued wealth increases; beyond reaching the middle class, additional wealth has less and less impact on meat quantity, and the wealthiest are increasingly choosing to consume less meat.
“the big consumption of meat comes at the change, so that big change in meat, comes when you go from very poor... to effectively some set over the middle classes... beyond that, the increase in wealth level has less and less impact on the quantity of meat you eat.”
Female education, especially in Sub-Saharan Africa, could shift global population trajectory by roughly a billion people.
- Female empowerment, especially the education of Sub-Saharan African girls over the next 30 years, could swing the world's eventual population by roughly a billion people, making it one of the most consequential interventions available.
“The world's population is going to be influenced by a billion people, according to whether or not we educate Sub-Saharan African girls over the next 30 years. And that, to me, is an astounding fact.”
- At a delicate moment when society is exploring the dark side of social media and misinformation, the more frightening risk is that fear about negative ideas leads us to slow down the spread of positive ideas, since the positives of connectivity massively outweigh the negatives.
“far more scary at the moment is, is being able to slow down those positive ideas for the fear about the negative ideas.”
Population restriction and immigration barriers counterintuitively increase global population by preventing equilibration and enabling stress-driven fertility.
- Restricting immigration not only has the social downsides being debated but will actually continue to drive up the world's population, because immigration helps equilibrium by letting people move where they can be supported, and because people under war and stress have more children (creating post-conflict baby booms), so reducing conflict and enabling movement are among the most significant ways to stabilize world population.
“if we shut up short now, if we put up walls, if we prevent immigration now... essentially it will continue to drive up the world's human population.”
- The rate of human population increase peaked around 1962 at about 2.2% and has declined substantially since, contrary to most people's intuition that growth is fastest now.
“it was around about 1962 the world's... The rate has come down of increasing around since then.”