Scientists say the world's population needs to be halved to save the planet, according to a new proposal published in the journal Sustainable Development.
Over the last 100 years, the global population has grown from less than two billion to 8.3 billion people. The researchers argue this growth cannot continue and that the population should be eased down to four billion by 2200.
Unlike the instant destruction depicted in the film Avengers: Infinity War, the researchers say the reduction would be a gradual decline. They believe most of the change could come from providing women in low income countries with family planning services.
"Easing to a smaller and sustainable population would not deprive additional billions of life but instead ensure that when they do arrive conditions will be good," the researchers write in the paper.
An impossible problem
The researchers say humanity's total impact on the planet equals each person's individual impact multiplied by the number of people on Earth. Because per capita resource consumption and waste production show no signs of falling, they argue the only way to reduce humanity's impact is to lower the population.
The team analysed the link between population and sustainability indicators. They found that over the past 50 years, during which the population doubled, CO2 emissions more than doubled, global biodiversity more than halved, and energy use tripled. Mineral extraction and pesticide use more than quadrupled over the same period.
"Our collective impact upon the planet's ecosystems has become overwhelming and unsustainable," the scientists write.
Conservative estimates suggest the population could reach 11.4 billion by 2100, which the researchers say would create a world with nearly double current CO2 emissions, energy and pesticide use, and quadrupled plastic waste. Separate research from Flinders University suggests the population could hit 12.4 billion by the late 2070s.
No coercion, researchers say
The researchers say the reduction could be achieved without force, unlike China's one child policy. "Gently ending and reversing population growth and moderating per capita impacts is a pro-nature and pro-human strategy," they write. "It will ease pressure on natural resources, lessen poverty in high fertility regions by way of smaller family sizes, reduce pollution, reduce resource and immigration conflicts, and improve quality of life in densely populated areas."
Instead of coercion, the researchers argue that empowering women to choose how many children to have will bring fertility rates down toward or below the replacement rate. "When women are free to decide how many children to have, fertility rates tend to fall toward replacement level or below, often rapidly," they write.
The researchers point to real world examples. In Iran, the introduction of family planning services caused the number of children per woman to fall from 4.08 in 1992 to 1.94 in 2001, below the replacement rate of 2.1. In South Korea, the fertility rate fell from 4.07 to 1.92 within 12 years of family planning services being introduced in 1972.
Around 200 million women currently do not have access to any family planning services, according to the researchers, contributing to exceptionally high fertility rates that they say could be lowered with targeted intervention.
Economic trade-offs
Even without coercion, the researchers acknowledge the approach would be controversial, since economic growth is closely tied to the availability of a young, working age population. In South Korea, people aged 65 or older already make up 20.7 per cent of the population.
According to the International Monetary Fund, further ageing could shrink the labour force by more than a quarter by 2050, leading to an average annual decline of 0.67 percentage points in potential economic growth.
Still, the researchers say this may be a price worth paying. "Ever-growing wealth and consumption are not ecologically sustainable, and the sooner our societies grapple with this inconvenient truth, the better," they write.
