Hans Rosling has always been an innovator when it comes to bringing big ideas to big audiences. The Norwegian doctor, statistician, and co-founder of the Gapminder Foundation has become known – to the kind of people who watch TED Talks anyway – for lively presentations aimed at demystifying common ideas about global development and demography. On Gapminder.org, he literally stands chest-high in water appealing for your donation to help him “cross the river of myths.”

Gapminder’s newest videos still have their trademark animated statistics and Rosling’s narration, but the aesthetic is simpler and they’re just over a minute long each. Taken together, they’re a great introduction to how we got to 7 billion people today and where we might be going next.

For most of human history, world population increased slowly. It took nearly 10,000 years to grow from 10 million people at the dawn of agriculture to 1 billion in 1800. But since then, thanks to advances in food production and health care, human population growth has been exponential, taking on a distinctive hockey stick-like trajectory to the present day (sound familiar?).

During this period of overall growth, however, the total fertility rate, or average number of babies per woman over her reproductive lifetime, was actually declining. Again, improved health care, which made it more likely children would survive to adulthood and easier for couples to control conception, played a role. But just as important were suffrage movements, which began the long process of releasing women “from lives previously dominated by childbirth and childcare,” as the London School of Economics’ Tim Dyson puts it.

Total fertility rates declined first in Europe, followed by the Americas and Asia. Africa’s fertility declined later and more slowly, and its future trajectory is the source of much debate.

How Accurate Have Projections Been?

What this means is that the rapid growth in global population over the last 200 years is slowing down and likely to taper off at some point in the next 100 years. As each successive generation has fewer children, the growth rate has declined, even as the total number of people continues to increase, given the sheer number of people of childbearing age.

Most countries are now at or near replacement-level fertility – just over two children per woman. The UN Population Division, which has long been the standard for demographic projections, predicts there’s an 80 percent chance that global population will increase to between 10 and 12 billion by 2100, then level off and eventually decline.

Rosling points out that the UN’s track record on these projections has been very good. The data that goes into demographic projections – local fertility trends and the number of people in different generations entering their childbearing years – is fairly accurate for most countries.

But because growth is now more concentrated, future projections are now almost entirely dependent on a much smaller sub-set of countries, namely those in sub-Saharan Africa and parts of the Middle East and South Asia. Fertility rates are already low in most of the rest of the world, and no country has ever rebounded from low fertility rates back to high once they’ve declined. This has created debate among demographers about to what extent these remaining regions with high fertility rates are outliers and whether they will follow a similar path as elsewhere. How quickly (or if) fertility rates decline in countries like Nigeria, Tanzania, Iraq, and Pakistan will determine where global population ends up peaking.

Empowering Women, Building a Virtuous Cycle

A good addendum to these presentations by Gapminder comes from the Sierra Club. The trajectory of future global population – the dotted lines in Rosling’s presentations – is in part dependent on expanding access to reproductive health care and empowering women to use it. More than 222 million women in the developing world have an unmet need for family planning. Reaching them as quickly as possible could not only help bend future growth toward lower estimates but also bring other benefits.

Women and girls who are able to stay in school and choose the number and spacing of their children tend to have smaller, healthier families, and are often more resilient to disruptions in their life, like the impacts of climate change, which can be devastating to the very poor or those dependent on subsistence agriculture.

Most of the world’s women with an unmet need for family planning live in developing countries, where carbon emissions per capita are currently just a fraction of more developed countries. But experts don’t expect wealth and consumption levels to remain so low forever (what’s the point of development, if so?). The Sierra Club points out that meeting the reproductive health needs of women to slow population growth could have the same effect on carbon emissions in the coming decades as eliminating deforestation, replacing every coal-fired power plant with solar, or doubling the fuel economy of every car on the planet.

This virtuous circle between women’s health, population dynamics, and the environment is why the Sierra Club is taking such an interest. “We can do the right thing for families while putting less pressure on our planet’s natural resources,” the video says. They’re not the only conservation organization focused on this nexus. WWF, Conservation International, and others have taken note of the connections between health, gender, and the environment, and there has been a push to include reproductive health and population dynamics in the Sustainable Development Goals, which are set to replace the Millennium Development Goals next year.

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So that’s how we got to today. Global population is not on track to grow forever – far from it in most parts of the world – but in some key countries it is still increasing rapidly, which has important implications for societies, the environment, and global development.