As population geographers, we focus on the spatial aspects of populations, or specific groups of people. Like where people are located, why they’re located there, and how the location and number of people impact a place.

Like in India we’re losing habitat in the region that is the genetic hearth, or birthplace, of many varieties of banana. [Gasp of horror?] So we might look at how the banana diffused as people travelled and then migrated along the Silk Roads over many centuries. Then we’d look at when the habitat started to decline and make note of who was using the land and how they were using it.

Maybe the density, or number of people per square kilometer, had changed, or the economic or political practices, or both. As the land use changes, we’d look for how humans have driven that change.

In fact, while worrying about natural resources and the impact of population feels like a very 21st century-climate-crisis-thing, scholars have been talking about overpopulation for a couple hundred years now.

Back in 1798 British economist Thomas Malthus first proposed what we now call the “Malthusian Prediction.” Based on what he was seeing in Britain where agricultural production was increasing linearly but the population seemed to be increasing exponentially, he concluded that the world would soon be overrun by people who would use up all the available resources. Malthus also argued that poverty causes population growth, and that adding more people to the planet would doom us all.

Today there are about 7 billion more people on the planet than in 1798, so Malthus hasn’t been right yet. But while many of Malthus’s ideas were disproven, the idea that poverty and population growth are linked stuck around. In fact, between the 1940s and 1960s it resurfaced as part of growing environmental awareness. This Neo-Malthusian movement pointed back to Malthus’s arguments, sounding an alarm that there were too many people on the planet, and soon there wouldn’t be enough resources for everyone.

Malthusian ideas -- like that we should be wary of outstripping our resources and that poverty is to blame -- led to global movements to encourage poor countries to achieve lower birth rates, but not everyone agreed with the rather convenient – for wealthy countries – argument that global environmental disaster was the fault of poor people. Like Danish economist Ester Boserup who in 1965 published what’s sometimes called the Boserup Theory or agricultural intensification. Unlike Malthus, Boserup argued that people innovate, and in particular, the agriculture sector only innovates when there’s pressure from having more mouths to feed. So poor people weren’t going to use up all the resources like Malthus thought, and disaster wasn’t imminent.

What Malthus and Boserup both were getting at were ideas of carrying capacity, which in human geography means how many people a given environment can support. Rather than blame over or underpopulation, today when population sizes increase or decrease, a population geographer will ask questions to figure out what’s happening in that place and how humans are putting pressure on the environment.

We also use the tools of demography, or the study of population, to study how populations change over space and time.

Demography often includes lots of statistics, like birth rate, which we’ve already mentioned and death rate, or the mortality rate. One tool demographers use is the demographic transition model which tries to approximate how different birth and death rates lead to population change and how that ties to the economy. In fact, it was originally created to model how population size might respond to changes in the economy -- like within or between agricultural, manufacturing, or even service-based economies.

Like any mathematical model, the Demographic Transition Model isn’t perfect because predicting the future is hard! In particular the Demographic Transition Model was developed based on population patterns in Western Europe and North America, and doesn’t always capture patterns in lower income or non-white populations.

And while we read the stages from left to right, when using the model it’s important to remember that economic development and population changes aren’t strictly sequential. It’s possible for dramatic events like a war or an environmental disaster to create conditions that cause populations and economies to skip back and forth between stages. But we’ll still talk through them from left to right.

In the Demographic Transition Model, Stage 1 populations have high birth and high death rates which end up balancing each other out more or less, so the population size is roughly small but steady. Before the industrial revolution every country would’ve been considered a Stage 1 country, but today none exist.

A Stage 2 population is one that is growing rapidly -- like the population of Western. Europe when Malthus was writing in the 18th century. Lots of people are being born, but fewer and fewer people are dying. Better healthcare and nutrition mean that people are living longer. In 2020, there were only a few countries considered Stage 2, like Yemen.

And to see what a high birth rate and low death rate means for the overall population and trends over time, we can use another demography tool called a population pyramid. A population pyramid allows us to see historic impacts on population, and also predict future growth and decline which helps governments allocate resources. From this pyramid, we can see that in 2020, there was a steady decline in population after 10 years old, and a sharper decline after 44 years old.

So this is a time as population geographers we can ask questions to see what’s happening in Yemen. Turns out, there’s been conflict and war in the region going back to at least 2011, and that dip represents some of the people who have died in the conflicts. But overall, a triangular pattern like this tends to indicate that the population will continue to increase.

While there aren’t many countries in the stage 2 category, in 2020, a large number of the world’s countries fit in Stage 3. This stage is where both death rates and eventually birth rates start to decrease. So our population growth rate starts to slow down.

In fact, the world’s population growth rate, or the rate of natural increase which only considers births and deaths and ignores migration, was actually at its highest in 1963. But in 2021, there’s still a lot of population momentum -- the birth rate might be getting smaller, but bigger and bigger groups of people are getting old enough to have kids. So the world population will still increase for a few more generations until the number of people who aren’t old enough to have kids is smaller than the number who are.

Which brings us to the final stage we’ll discuss: Stage 4 where countries have slow to declining population growth. Across Eastern Europe there’s been an economic stagnation after the wars and economic decline of the 1990s. And instead of leading to high birth rates like might happen with a Stage 1 or 2 country, the lack of economic opportunity leads to voluntary migration -- kind of a double population whammy.

As people leave, there are fewer people to support the economy and take care of the aging population. So stage 4 countries, like Japan or Germany, or even some Stage 3 countries like Estonia, are trying to create incentives for people to both stay in the country and have more children.

What we can learn from demographic tools like the Demographic Transition Model or by studying population pyramids is that the interplay between birth rates, death rates, and migration requires a lot of context. But we can use this information to better understand the relationship between people, their economic security, and their impact on the resources they use.

Globally there’ve been drastic efforts to reduce population sizes in the name of saving the environment or resources -- like restrictions on the number of children a family can have, or even forced sterilization programs. But by looking at more than just population size, we can notice that most places where the birth rate comes down have a few things in common, especially economic security and the role of women in society.

In societies where economic security is shaky, or where children rarely make it to adulthood, or where there is no guaranteed retirement income, there’s often a high birth rate. And countries have found that if they want to encourage a decrease in birth rate, one of the fastest ways to help that happen is to empower women. Many different studies show each year of education a woman has decreases the birth rate by 5 to 10%.
And education combined with access to good paying jobs is a major factor in the total fertility rate or the average number of children a person is expected to give birth to over the course of their reproductive years.

A population geographer uses all of these tools to assemble the population trends into a picture that helps us understand the role they play in economic and environmental issues. Societies can then use this picture for decision-making. Like to understand the current population trends and predict the future trajectory to better plan for workforce and resource needs, or to implement policies to educate women and encourage them to participate in the workforce to try to decrease future population pressure.

So, is the world overpopulated or underpopulated? It seems to be both.  It just depends on where you’re located. The global population is increasing, but some countries like Estonia, Japan or to some extent the US face an aging crisis -- a huge chunk of their population is getting older without enough younger people to care for them. Other high density places like Bangladesh, India, and South Korea have implemented a wide range of programs, or have economies that give people economic options that make it more possible to have smaller family sizes.

If we want to understand how to address some of our largest ecological and social tensions, we need to understand more than just how populations grow. We have to understand what makes people feel economically secure, but keep in mind that economic success uses up a lot of resources.

So rather than go “Ah! There are almost 8 billion people on the planet!” it’s more helpful if we remember we’re talking about people with complex lives and dreams, living in particular economic situations, not just numbers, and look at multiple factors to understand the problems related to population size.

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