Pope Francis is no stranger to controversy. But his latest statement saw jaws drop around the world, especially coming from a man who once declared that pets had an afterlifeIn 2014, Francis claimed that dogs can join their owners in heaven, a view that contrasts with conventional Christian teaching..

Speaking to the public, the soft-spoken pontiff blasted those who keep pets but refuse to have multiple children. He called this practice a "form of selfishness" that "takes away our humanity." 

This is the latest salvoShooting multiple weapons at once, often with the aim of bringing down a target in a single blow. in his battle to promote the traditional family. But Francis' concerns also reflect a global issue. Although the world population is rising as a whole, birth rates are declining in many countries. DemographersAcademics who specialist in demography, the study of human population growth and decline. believe that this downward turn will eventually infect the globe.

These changes hit close to home for the Bishop of RomeYet another title of the Pope, who has direct control over the 711 churches in Rome and its surroundings. . By 2100, Italy's population is expected to shrink from 61 to 28 million. By 2050, the Italian death rate will be twice its birth rate. Similar levels of decline are expected in 22 other countries, including Japan, Spain and Thailand.

The Pope's comments connect in particular to the falling global fertility rateThe average number of children born to women of a certain age. . Between 1950 and 2020, this sank from 4.7 to 2.4; it is expected to plummet to 1.7 by 2100. In the same timeframe, life expectancy has increased from 45.7 to 72.6 years. Fewer people are being born but those alive are living longer.

Many agree with Francis that these two trends threaten a crisis. As the elderly population grows, the working minority will have to give up more time and income to care for them. Economic growth and innovation will grind to a halt.

Some say this is already happening. As writer and researcher Robert Colvile puts it: "Britain is turning into an elderly care system with a state attached." The young might even become the servants of the old.

Yet equally loud voices claim that this view is too short-sighted. Improvements in healthcare might allow elderly people to remain active for longer. A smaller population could make everyone richer as work becomes more valued. Between 2009 and 2017, Japan's population declined while the wealth of each individual increased.

According to demographer Sarah Harper: "Falling fertility is good. It's good for the planet, it's good for communities and it's good for work." David AttenboroughAn English broadcaster and natural historian known for his wildlife documentaries. , Miley CyrusCyrus had slated that she will not have children until a solution for climate change has been found. and Prince Harry have all argued that restricting further growth will help preserve the planet and our diminishing natural resources. 

Others claim that we should actively try to reduce the world population. The Earth has already reached capacity, and any growth will make our lives worse.

Improvements have often come alongside a growing population. Between 2010 and 2021, the number of people in the world increased from 6.9 billion to 7.9 billion. In the same time period, the proportion of people living in poverty decreased from 16% to 9%.

As a whole, the human population has always grown. An overall decline is a new frontier. Whatever the consequences, they will be huge.

Yes: From the Industrial Revolution to the baby boom, population growth has walked in step with an improved quality of life. A population decline might lead to the opposite.

No: A smaller population will give each person more space and access to resources. It might even give the Earth itself more room to breathe, as emissions decline.

Or...? Population decline might be a crisis but not a catastrophe. It will force humanity to make many changes - but whether they are for the good or the bad is up to us.