Currently, our planet’s population is doing something once thought nearly impossible: it’s expected to peak much sooner than many predicted, potentially topping 10 billion by the 2060s before beginning to fall. In wealthier countries this trend is already visible. For example, Japan’s population is shrinking by about 100 residents every hour. Meanwhile, birth rates have plunged across Europe, the United States, and East Asia, and the decline is likely to spread to many middle- and low-income countries.
A university team led by demographer Andrew Taylor and climate-and-health researcher Supriya Matthew has been studying this shift. They recall that just a decade ago demographers projected the global population could reach 12.3 billion—far above today’s 8 billion. For decades some ecologists tried to protect the environment through population-control strategies. Now we face a very different reality: population growth is slowing without deliberate policy, and populations in wealthy countries are already declining.
What does this global population decline (depopulation) mean for the environment?
Depopulation is already underway. For much of Europe, North America, and parts of northern Asia, populations have been falling for decades. Birth rates in those places have been dropping for roughly 70 years and remain low. At the same time, longer life expectancy has doubled the number of very elderly people (those over 80) in the last 25 years. Until recently China was the world’s largest country by population, making up about one-sixth of Earth’s people. Now China’s population is shrinking rapidly, and Science Alert reports that decline is expected to speed up. Expert forecasts suggest that by the end of the century only about one-third of China’s current 1.4 billion people will remain.
Japan, once among the world’s most populous countries, may see its population halved by the end of the century. This is part of the demographic transition: as countries move from agrarian economies to industrial and service-based ones, birth rates fall sharply. When low birth rates coincide with low mortality, the overall population shrinks. A big factor is that more women pursue education and careers; they are having children later and fewer children on average.
Population decline creates real economic challenges. The working-age population is shrinking while the number of elderly people who need support is growing. By 2100, researchers predict only six countries will have birth rates above death rates: Samoa, Somalia, Tonga, Niger, Chad, and Tajikistan. In contrast, birth rates in about 97 percent of countries are expected to fall below the replacement level (2.1 children per woman).
Will nature get a break when the population decreases? Not necessarily. The picture is more complicated. For example, people consume the most energy between ages 35 and 55. After that consumption falls, then rises again after about age 70—partly because many older adults live alone or stay at home in larger houses. The dramatic rise in the elderly population this century could offset the drop in consumption you might expect from fewer people. It’s also crucial to consider the huge differences in resource use and carbon footprints between countries: wealthier nations use far more. So as more countries become wealthier and healthier but have fewer children, a larger share of the global population could still drive higher emissions.
Expect more liberal immigration policies that could boost the working-age population. Migration levels have already exceeded projections for 2050. When people move to developed countries, it can be economically beneficial for both migrants and the destination countries. But from an ecological perspective, that can mean higher per-capita emissions and greater human impacts on ecosystems, since income and emissions are closely linked.
As the world warms, forced migration—when people must leave their homes to escape war, drought, or other climate disasters—is projected to push as many as 216 million people to move over the next 25 years. Where those people end up could change emission patterns. If you ignore all these interacting factors, fewer people should, in theory, ease pressure on nature. But unless we cut emissions and shift consumption patterns, especially in developed countries, a smaller population alone won’t guarantee environmental relief.
