Australian study suggests there is no stopping population growth, leading to less sustainability by 2100 unless nations implement effective strategies

A planet-wide conflict that claimed as many lives as the first two world wars combined would hardly make any difference to the world’s exploding population, according to a study.

Population growth is so out of control that even stringent restrictions on childbirth, disastrous pandemics or a third world war would not make it manageable by the turn of the next century, researchers claim.

Rather than reducing the number of people on the planet, cutting the consumption of natural resources and enhanced recycling would have a better chance of achieving effective sustainability gains in the next 85 years, they said.

Barry Brook, who co-led the study at the University of Adelaide, Australia, said: “We were surprised that a five-year World War III scenario, mimicking the same proportion of people killed in the first and second world wars combined, barely registered a blip on the human population trajectory this century.”

World War II claimed between 50 million and 85 million military and civilian lives, according to different estimates, making it the most lethal conflict by absolute numbers of dead in human history. More than 37 million people are thought to have died in World War I.

The scientists used a computer model based on demographic data from the World Health Organisation and US Census Bureau to investigate different population reduction scenarios.

They found that under current conditions of fertility, mortality and mother’s average age at first childbirth, global population was likely to grow from seven billion in 2013 to 10.4 billion by 2100.

A family takes a selfie next to a boy in front of a giant basket of flowers on display at Tiananmen Square in Beijing. The study suggests that even a worldwide one-child policy like China’s implemented over the coming century would still likely result in around 10 billion people by 2100. Photo: Jason Lee/Reuters

Climate change, war, reduced mortality and fertility, and increased maternal age altered this prediction only slightly.

A devastating global pandemic that killed two billion people was only projected to reduce population size to 8.4 billion, while six billion deaths brought it down to 5.1 billion.

The findings are published in the journal Proceedings of the National Academy of Sciences.

Under current conditions of fertility, mortality and a mother's average age at first childbirth, global population is likely to grow from seven billion in 2013 to 10.4 billion by 2100

Co-author Corey Bradshaw, also from the University of Adelaide, said: “Global population has risen so fast over the past century that roughly 14 per cent of all the human beings that have ever existed are still alive today. That’s a sobering statistic.

“This is considered unsustainable for a range of reasons, not least being able to feed everyone as well as the impact on the climate and environment.

“We examined various scenarios for global human population change to the year 2100 by adjusting fertility and mortality rates to determine the plausible range of population sizes at the end of this century.

“Even a worldwide one-child policy like China’s, implemented over the coming century, or catastrophic mortality events like global conflict or a disease pandemic, would still likely result in five to 10 billion people by 2100.”

Nine different scenarios were constructed, ranging from “business as usual” population growth to highly unlikely disasters resulting in billions of deaths.

Brook, now at the University of Tasmania, said: “As our models show clearly, while there needs to be more policy discussion on this issue, the current inexorable momentum of the global human population precludes any demographic ‘quick fixes’ to our sustainability problems.

“Our work reveals that effective family planning and reproduction education worldwide have great potential to constrain the size of the human population and alleviate pressure on resource availability over the longer term.

“Our great-great-great-great grand-children might ultimately benefit from such planning, but people alive today will not.”

Bradshaw added: “The corollary of these findings is that society’s efforts towards sustainability would be directed more productively towards reducing our impact as much as possible through technological and social innovation.”