Scholars have struggled with population concerns since ancient times. Plato expressed worries about overpopulation in Athens and advocated for strict population control measures managed by the state. He proposed limiting the ideal city to 5,040 citizens and emphasized the importance of moderating consumption.

Thomas Malthus, an English economist, continued this discourse in 1798 with his work “An Essay on the Principle of Population.” Malthus highlighted the inevitable clash between human population growth and the planet’s finite resources. His negative perspective emphasized the pressing need for addressing population growth and its impact on resource sustainability.

Controlling the size of the population, known as population engineering, is a deeply divisive area. Today, any policies involving quotas or targets to increase or decrease the human population are almost universally condemned. The risk of these incentives leading to pressure or other violence is seen as too great. However, there is little agreement beyond this.

At one end of the spectrum lie those who see lower fertility rates in some areas as a crisis. One demographer is so concerned about the localized drop in the birth rate in the U.K. that he has suggested taxing the childless. As of 2019, there were 1.65 children born in the country per woman on average. This is below the replacement level, the number of births required to maintain the same population size, of 2.075.

The opposing view is that slowing and eventually halting global population growth is not only eminently manageable and desirable but also achievable via entirely voluntary means, such as simply helping women avoid getting pregnant and providing education. In this way, proponents of this position believe we could not only benefit the planet but also improve the quality of life experienced by the poorest citizens worldwide.

On the other hand, many advocate for shifting the focus to our activities and consumption habits. Supporters argue that the quantity of resources each person uses up has greater influence, and they point out that consumption is significantly higher in wealthier countries with lower birth rates. Reducing our individual demands on the planet could lower humanity’s footprint without hindering growth in poorer countries.

Amid all the controversy and uncertainty, it can be hard to know what to think. There are several ways in which the number of people on the planet might affect a few key aspects of our lives in the future—the environment, economy, and our collective well-being.

As more humans inhabited the Earth, they began to adapt the land for their use. According to the UN Food and Agriculture Organization, 38% of the planet’s land surface is currently used to grow food and other products for humans or their livestock. Today we are the dominant species on land.

As our dominance increases, many environmental changes have been occurring in parallel. A growing number of women are joining the movement to have fewer or no children. The trend was fueled by research from 2017, which calculated that, in the developed world, simply having one fewer child could reduce a person’s annual carbon emissions by 58.6 tons, more than 24 times the savings from not having a car. In contrast, many environmentalists now believe that the problems we are currently facing are largely due to consumption rather than overpopulation, which shifts the blame away from poorer countries and toward wealthier, high-consumption nations. Many developed countries are already densely populated, and this is partly how they achieved their wealth. Denying developing countries this opportunity is seen as unfair. Some argue that the idea of an impending “population bomb” coming to destroy the planet is outdated. They point out that in the past, population trends grew rapidly, but today there are fewer than 10 countries with fertility rates over 5.

Demographics influence more than just the environment and economy. They are also a powerful hidden force in shaping the quality of people’s lives worldwide.

According to one study, a country’s prospects are determined by the rate of population growth or decline, not by the absolute number of people in the country. Therefore, what matters most is not the size of the population but whether or not the government has the resources to improve its infrastructure in order to maintain the correct level of access to those services for its citizens. In light of this study, the longer it takes for a country to reach a certain population, the greater the likelihood that its government will be able to establish the right structures in the system that will support that population. Governments in countries with high population growth should therefore set up policies to slow down the rate of growth.

One factor with a well-documented role in slowing down this rate of growth is the education of women. As women get access to education, they begin to work outside the family, which competes with childbearing. However, we need to emphasize the merits of education independent of its impact on population size. This gets to the heart of one modern view on population engineering—policies should be implemented for the benefit of society, and if they happen to lead to beneficial demographic changes, that’s just a bonus.

We should make the necessary investments to get to the rate of growth that is consistent with where countries want to go. That is the magnitude of the opportunity that exists. The decisions made by governments across the globe over the coming decades will be greatly influential in determining how many people there are on the planet.

The United Nations Population Fund (UNFPA) released a report warning against government policies targeting fertility rates, emphasizing the potential erosion of reproductive and human rights. The report, titled The State of World Population report 2023, highlights the danger of such policies undermining rights in various regions. It argues that human reproduction is neither the root cause nor the solution to major global challenges like climate change, pandemics, conflicts, and economic uncertainty. Instead, the report advocates for public investments to ensure equitable access to education, employment, healthcare, and social protection. It stresses the importance of not treating the bodies of women and girls as instruments to enforce population goals. The report also reveals that only 56 percent of women have control over their sexual and reproductive health and rights.

The UNFPA’s report includes data showing there is substantial anxiety in the general public about the population after surveying 7,797 people across eight countries (Brazil, Egypt, France, Hungary, India, Japan, Nigeria, and the United States). The most common view was that the world’s population was too large and the fertility rate too high. It also found that the more exposure people had to the media and conversations about population, the more likely they were to be concerned about population numbers, the fertility rate, and immigration.

“The question isn’t whether the human population is too large or too small,” Natalia Kanem, the executive director of the United Nations Population Fund, said. “The question is: Can everyone exercise their fundamental human right to choose the number and spacing of their children? Sadly, the answer is a clear no.”

The report cites cases in which population targets set by governments are pushing people toward reproductive choices they may not otherwise make.

In Uzbekistan, for example, doctors have spoken to the international media about pressure to use sterilization to reduce the population rate, with the government arguing that poorer patients can’t afford more children. In Russia, “mother heroines” with large families receive financial incentives. Other countries, like Romania and the United States, have faced abortion restrictions. India proposed a two-child policy with sterilization incentives and penalties for exceeding family size limits. South Korea, which has the world’s lowest birth rate, is now offering families payments and other benefits to anyone who gives birth to a child. United Nations experts say these policies generally don’t work in the long term.

“Such measures will not help in any meaningful way to reverse fertility trends,” said Michael Herrmann, senior adviser of economics and demography to the UNFPA. He told the press briefing that demographic changes might cause some of the challenges the world faces, but “manipulating population numbers” isn’t the solution, as these measures often only encourage people to have children earlier, not more of them.

Kanem said women in less-developed countries are often blamed for having too many children, while women in developed countries are blamed for having too few.

“This fallacy holds the wrong people to account,” she said.

“The countries with the highest fertility contribute the least to global warming and suffer most from its impacts.” According to Kanem, focusing only on fertility rates distracts from solutions such as reducing carbon emissions and consumption in wealthy countries.

The report also said most experts today agree that “population changes are normal, and population sizes are neither good nor bad; what is needed are resilient systems that can respond to the needs of a population, no matter what its size.” That includes advancing gender equality overall. In high-fertility countries, the report said, “empowerment through education and family planning” will lead to economic growth. Conversely, in aging, low-fertility countries that are concerned about labor shortages, gender parity in the workforce is considered the most effective way to improve productivity and income growth.

In Canada, where the fertility rate is low, some experts say the solutions that best tackle economic concerns are through supportive government policies.

“Some of the responsibility of taking care of children needs to be taken off women’s shoulders,” said Marina Adshade, an economics professor at the University of British Columbia in Vancouver. Adshade said policies that require or encourage more men to take parental leave, more flexibility for both women and men at work, and affordable child care would all make a big difference. “It’s just simply not going to work if you’re just repeatedly telling women that they have to make sacrifices for the greater good,” she said.

For a generation of young people, the choice not to have children is rooted in a lack of policies that support future generations. In 2019, Emma Lim, a fourth-year student at McGill University in Montreal, launched a movement called #NoFutureNoChildren—a pledge not to have children until the Canadian government takes serious steps to fight climate change. So far, she’s sticking to it, saying her reluctance isn’t limited to climate change policies.

“We have a cost-of-housing crisis. We don’t have a very strong financial future. When you add climate change ... it just doesn’t look like a promising world,” Lim said.

This echoes the UNFPA report, which states that family planning without “improving the low status of women and girls around the world will likely have only a limited impact on broader economic and social development.”