A fertiliser process helped humanity grow from 1.6 to 7.7 billion
In 1800 about 1 billion people lived on Earth; by 2025 there were 8.2 billion. A key reason was the Haber process, which let farmers make nitrogen fertiliser from the air and has been called the detonator of the population explosion. Yet one influential scientist argued the real driver was simply better food, not medicine.
Human numbers have climbed steadily since the Black Death ended around 1350. Growth quickened in the West during the Industrial Revolution and surged after the 1950s thanks to medical advances and more productive farming. Fritz Haber's method of fixing nitrogen transformed food production, and world population, 1.6 billion in 1900, had reached 7.7 billion by November 2019. Today the planet adds roughly 70 million people a year, about 0.85 percent.
That pace is well below the peak of 2.2 percent a year reached in 1963. Many wealthy countries have passed through the demographic transition, in which higher living standards bring much slower growth, while poorer regions are still growing fast. The United Nations, in its 2024 projections, expects the global total to top out in the mid-2080s at around 10.3 billion, a figure it has repeatedly cut as birth rates tumble, though some researchers argue recent forecasts underestimate future growth.
Why did the population boom begin? The British health scientist Thomas McKeown, who lived from 1912 to 1988, argued that nineteenth-century Western growth came less from more births than from fewer deaths, especially among children and infants. He credited rising living standards, above all better nutrition, and doubted that sanitary reform, vaccination, quarantine or curative medicine did much until well into the twentieth century. The McKeown thesis has been fiercely disputed, yet newer studies have supported parts of it, and he shaped the thinking of the Nobel economists Robert Fogel and Angus Deaton, who called him the founder of social medicine.
Growth also carries costs. Combined with rising consumption, a larger population drives biodiversity loss and climate change through overuse of natural resources. Reducing population is sometimes proposed as a sustainability tool, though its scope is limited by respect for personal choice. International policy mostly works through the Sustainable Development Goals, aiming to raise living standards while shrinking humanity's environmental footprint.
Source: Population growth
