- For most of my life, experts have been warning us about the dangers of exploding population growth.

And that makes a lot of sense, right?

It took 300,000 years for the global population to reach 1 billion, but only about 200 years to go from 1 billion to 8 billion.

But all that growth is slowing down, and based on current birth rates, it will eventually stop.

The United Nations projects that the global population will peak at 10.4 billion before the end of the century, and then decline.

Other projections say it will happen even earlier, and peak at 9.7 billion by 2064.

This is one of the most fundamental demographic shifts in human history and economists, policy experts, and tech billionaires are freaking out about it, calling population decline an existential threat.

So is the population exploding or collapsing?

And what does it mean for the future?

I'm Sinead Bovell, and this is "Far Out."

[upbeat music] In 1950, women on average gave birth to five children.

Today that number, also known as the total fertility rate, has halved to 2.3.

Access to contraception, education, and jobs has led to more women delaying childbirth and having fewer children.

Today, two thirds of the global population live in a country where the fertility rate is below the replacement rate, at 2.1, which is the number of children needed to keep the population stable.

So if the current fertility rate stays the same, then by the end of the century, South Korea's population will contract by 62%, Poland and Japan will shrink by half, and Italy and Thailand will be down by about 44%.

Oh, and then there's China.

The most populous country on the planet for centuries reported its first population decline in six decades in 2023.

By the end of the century, it will shrink by half.

This decline isn't happening at the same rate all over the world.

In the US, while the fertility rate is well below the replacement rate at 1.7, the population is still expected to increase modestly by 2050 because of migration.

And birth rates are still high in some countries.

For instance, more than half of the globe's population growth in the next 30 years will come from countries in Sub-Saharan Africa, especially these four countries.

But demographers expect that eventually, fertility rates in Africa will follow the trend of the rest of the population.

- And I think we're at this moment in human history where we are trying to figure out if low fertility rates are an aberration or the new normal.

I say they're the new normal, particularly for the next couple of decades.

And the way population works is math.

So if it's low for a couple of decades, that means fewer babies right now who will then age into their reproductive years as smaller cohorts.

So even if their fertility rates go up a little bit, it's a momentum towards smaller.

- Demographers like Jennifer Sciubba have been tracking this momentum towards smaller for decades.

At first glance, a shrinking world might seem like a relief, especially as we hurdle towards a future with more climate disasters and less biodiversity.

But here's the problem, this demographic shift isn't happening fast enough to matter in terms of climate change.

Experts have been saying for years that we need a global transition to clean energy now if we want to get closer to our target of net zero emissions by 2050, a goal that most of the world isn't on track to reach.

And focusing too much on population decline, especially in poor countries where fertility rates remain high, also obscures the fact that it's high income countries that contribute the most to the problem of climate change.

- And my fear is that we will pedal the line, oh, good, the environment will be fine because our population is shrinking.

And that will be an excuse for inaction, because really it's about how much we consume.

- Here's the other problem with pinning our hopes on a shrinking world.

Even though fertility rates are shrinking, we're still adding roughly 130 million people to the planet every year.

That's because the number of women in the reproductive age bracket has tripled since 1950.

That means the number of births will stay high for a few decades, even as women are having fewer children, because there's simply more women that are the right age to have children.

Life expectancy is also twice as long as it was a few generations ago.

So if we're still adding millions of people to the planet every year, why are people worried about population collapse?

In places where birth rates have been low for decades, the demographic chart looks like this.

More older people than younger people, that means fewer future consumers and taxpayers.

Mix that with an aging population, straining social programs, and you might have an economic crisis on your hands.

- The reason so many private and public sector leaders are worried about population shrinking is because they see consumption as the driving force of the economy.

And they will do everything they can to make sure that consumption stays high.

Well, that may be antithetical to our environmental goals.

- A growing number of countries now have policies that try to raise birth rates, but we know from history that trying to coerce birth rates can sometimes lead to human rights violations.

For lowering birth rates, that can look like forced sterilization and abortions.

And for raising birth rates, there are subtle, but still dangerous, policies, like propaganda designed to pressure women to stay home and have more children.

Research shows that even benign policies like cash payments lead to only temporary bumps in the fertility rate.

Experts say that rather than reaching for an ideal population size, we should support women and families to have the number of children they actually want to have.

This trend of low birth rates can't be fixed with a simple on/off switch.

The future is already written.

Most people who will be alive in 2050 have already been born.

And population decline is largely a story of success, longer, healthier lives, and crucially, more freedom and opportunity for women.

There's also a saying that experts keep repeating, demography is not destiny.

In the 1960s when the world population was less than half the size it is now, the bestselling book, "The Population Bomb" predicted mass planet-wide food shortages and chaos.

But that didn't happen.

Instead, we invented new agricultural techniques, like improved seeds, high intensity fertilizer, and drip irrigation.

We can still prepare for the future, it just might include adapting to a smaller and older world.

[upbeat music]