Between 2 and 26 billion? Study projects human population up to 2300

Population models generally don’t extend beyond 2100 because high uncertainty makes it very difficult to project demographic trends far into the future. An interesting recent study, however, uses sophisticated models to provide a rough idea of what our far-future population might look like.

Extending the UN’s probabilistic population models, the paper, published in the International Journal of Forecasting, found that our population size in 2300 will likely be between 2 and 26 billion people, with a median projection of 7.5 billion.

Why look so far into the future?

It may seem silly to forecast population all the way to 2300, given that within such a large time frame, pretty much anything could happen. To put things into perspective, imagine a newborn in 2300, and assume one generation is 30 years – this future baby’s great, great, great, great, great, great, great grandparents haven’t even been born yet. The large population size range for 2300 reflects the high degree of uncertainty relating to the many variables that go into population models, including fertility, longevity, mortality and migration patterns, and demonstrates how small changes in some of these variables can result in vast differences in future population sizes.

The authors argue that far-future projections could also be valuable for climate modeling. Population trends are a key input into the Intergovernmental Panel on Climate Change (IPCC) models, which lay out potential warming scenarios. Having a better idea of possible population trajectories also helps calculate the “social cost of carbon,” which quantifies the societal damages from carbon emissions and informs policy decisions.

Possible scenarios

The most recent UN projections published in 2022 show our population will likely reach 9.7 billion in 2050, up from 8 billion today. After this date, uncertainty increases dramatically, explain the study’s authors, as by the end of this century, the majority of the population will be made up of people who haven’t yet been born.

In the International Journal of Forecasting study’s median scenario, the global population is 11.1 billion in 2100, 10.4 billion in 2200 and 7.5 billion in 2300. The global fertility rate (the average number of births per woman), currently at 2.3, is expected to decline steadily until 2250, after which the model predicts it will stabilize at country-specific levels below the replacement level of 2.1.

The populations of Asia, Europe, and Latin America are projected to peak well before the end of this century and then decline substantially, while the populations of Africa and Northern America are projected to peak much later, in the 22nd century. In Africa, this is due to currently high fertility as well as population momentum (a high proportion of the population currently in reproductive ages). In the case of Northern America, it is largely due to the authors predicting high immigration compared to other regions, modest population momentum, as well as fertility that is closer to replacement level than on other continents. Nevertheless, the median forecast for Africa in 2300 is 3.9 billion compared to only 301,000 for Northern America.

Assumptions and limitations

The study, while published this year, uses the UN projections from 2019 instead of the newer 2022 data set. Importantly, the 2022 data showed for the first time that global population will likely peak this century, at 10.4 billion in the 2080s, and then remain at that level until the 22^nd century.

The paper also assumed that China’s population would not peak for another decade, but as was revealed last month, this has, in fact, likely already happened. Hence, the study’s projections would likely have been slightly lower had they incorporated the most recent population data.

The authors note that other attempts to model far-future population trends have projected ranges comparable to their 95% confidence interval of 2.3 to 25.8 billion in 2300. They argue that their models provide a more refined picture, as in addition to extending the sophisticated UN methodology, the resulting projections were reviewed by a panel of demographers, and then further modified based on the panel’s feedback.

For example, for the 95% interval, the models initially yielded a total global fertility rate of between 1.66 and 2.23 births per woman by 2300. However, the expert panel argued the lower bound was too high, as there are many countries that currently have a fertility rate below 1.66. South Korea is the most extreme example, with a fertility rate of only 0.8.

The authors also assumed that the global fertility rate would not drop below 1.2 births per woman, and that it would not stay at this low level for long. Their reasoning is that a global fertility rate of 1.2 from 2250 onward would lead to a population reduction of about 40% per generation, and a 98% drop over two centuries.

The authors note,

“The human species would then be on a path to extinction. It seems at least plausible that humanity would act collectively or individually well before that point to avoid such an outcome.”

Another assumption was that, by 2300, life expectancy in most countries will have reached the high 90s, and that with populations aging, international migration will decrease in the long term, as this is mostly undertaken by younger people aged between 15 and 35.

Perhaps the study’s biggest limitation is that it doesn’t include potential impacts of climate change and related environmental disasters. The authors acknowledge this, claiming that there is not yet sufficient scientific consensus about the likely extent of global impacts of the climate crisis.

Utopia or dystopia?

Given that it is highly unlikely that people and nature could thrive in a world of 26 billion, we should clearly strive towards the lower end of the projected range. Removing barriers to family planning, education and women’s rights is critical to achieving a more sustainable, happier, healthier population.

All population projections for hundreds of years from now should be taken with a large pinch of salt, but they nevertheless provide an interesting thought experiment and reinforce the need to act now for a better future.

What do you think our population will look like in 2300? Will we live in a sci-fi dystopia or will we finally be living in harmony with the natural world? Will we have experienced terrible mortality events, or will we have gradually and gracefully shrunk our human footprint through choice? Will humanity even still exist? I’d love to hear your thoughts! Feel free to email me with your predictions or wishes for the distant future at onater@populationconnection.org.