Elon Musk steps onto the stage at a conference in Italy. In three decades, the world's population will be "one tenth of its current size", he tells the audience. The birth rate, he adds, "is maybe half the replacement rateThe rate of births needed for babies to replace their parents. ".

In fact, the global birth rate is above the replacement rate and the global population is set to rise over the next few decades. Across Europe, America and Eastern Asia though, fertility rates are falling.

The fertility rate is the average number of babies born to each woman. In England and Wales that number has reached 1.44 - the lowest rate since 1938.²

For a population to remain the same, the fertility rate needs 2.1 babies per woman. However, in Japan the rate is 1.21, in Taiwan 0.865 and in South Korea just 0.72.³

EconomistsExperts in economics, the branch of knowledge concerned with the production, consumption and transfer of wealth. disagree about whether this is a problem. Some argue that, if the population declines, the number of people paying taxes will also shrink. This means governments will struggle to pay for basic services.

One solution is immigration, which keeps the population growing. But, as journalist Annabel Denham warns, the levels of immigration that may be needed in the future could cause "social unrestA state of general dissatisfaction expressed in unconventional and sometimes violent ways.".⁴

According to UN projections, the global population is likely to peak at 10.3 billion in the next 60 years. Population growth in Africa, Central Asia and Southern Asia will offset any decline in Europe and America.⁵

Even if these figures are wrong, a decline in the global population might have long-term benefits. By reducing the demand for food and energy, it will slow the pace of global warming and environmental destruction.

A shrinking population also brings opportunities. Not having a family gives people - especially women - more freedom to pursue their own lives. Meanwhile, AI, automation and bringing older people back into employment could make up for a smaller workforce.

So Elon Musk is wrong to say that "it should be considered a national emergency to have kids".⁶ Yet, even if the Earth is not running out of humans, declining populations also mean the loss of languages, cultures and communities. When couples have children, it suggests they are hopeful about the future. Right now, too many people feel the opposite.

Is Planet Earth running out of humans?

Yes: Fertility rates are falling across America, Europe and Eastern Asia. Most government interventions do nothing to slow the trend. Musk is right to warn about the coming crisis.

No: Globally, the population is growing and expected to peak in the second half of the century. Immigration, AI and automation can solve shortages in the workforce.

Or... The global population may be growing, but declining birth rates in many developed countries suggest that people no longer feel the security, stability or hope needed to start a family.