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Dr Catherine Conlon Are there too many humans?

Falling fertility rates challenge the global economy but continued population growth is unsustainable, writes the public health expert.

THREE OUT OF every four nations are projected to have fertility rates below population replacement birth rates by 2050, according to a new study.

Plummeting fertility rates in most countries over the next quarter century will leave growth concentrated in a minority of low-income states in sub-Saharan Africa and Asia that will have far-reaching social and economic impacts, the research published in the Lancet, warns.

“The implications are immense,’ said Natalia Bhattacharjee, co-lead author of the study and lead research scientist at the Institute for Health Metrics and Evaluation. ‘These future trends in fertility rates and live births will completely reconfigure the global economy and the international balance of power – and will necessitate reorganising societies.”

Global births

The study of 204 countries and territories forecasts three quarters (76%) will dip below population replacement rates by 2050 and almost all (97%) will reach that point by 2100. Sub-Saharan countries are forecast to account for half of global births by 2100.

It focuses on the potentially transformative impacts of falling fertility rates on world order and economic growth. Conversely, scant attention is given to the reality that continued exponential global population growth on a planet with finite resources is unsustainable and far more catastrophic.

The UN forecasts the global population could grow from the current figure of about 8 billion to 9.7 billion in 2050 and peak at nearly 10.4 in the mid-2080s.

Ireland’s total fertility rate has almost halved (1.76 in 2021) compared to 1950 (3.18), when there were three children born to every woman capable of giving birth. It is predicted to continue falling to 1.54 by 2050 and 1.40 by 2100.

Researchers here point out there is no ‘silver bullet’ to mitigate the trends being seen, although social policies like enhanced parental leave and free childcare could provide a ‘small boost’ to fertility rates.

The paper focuses on the societal and economic headaches falling fertility rates will cause in developed countries; in terms of how economies will fund pensions and survive the loss of taxation resulting from so many workers leaving the workforce at the same time. The dependency ratio – the number of adults and children in the economy depending on tax revenue from a diminishing pool of workers is seen as the key problem.

There are three solutions – to raise fertility, reduce mortality or increase migration – with only the latter likely to have a significant impact. The reality is that, at a time of heightened migration in recent years aggravated by war, climate change and poverty, migration is viewed in most developed nations as an unsustainable hindrance to economic prosperity.

Too many humans?

The real question that needs to be asked is whether there are already too many humans on the planet and whether falling fertility rates, globally and in developed countries, is a singular opportunity for the planet to realign itself within planetary boundaries and address wealth inequality.

Earth’s biosphere is spectacularly abundant, capable of supporting billions of humans and species. But that wonderful psychedelic menagerie is under threat.

That biosphere supports the planet by providing food, water, oxygen, waste removal, a stable and temperate climate and protection from harmful solar radiation. These systems do not exist in isolation but are powerfully interconnected. You can’t grow food without water and the distribution of water across the globe is dependent on a stable climate.

When the human population grows to a point that puts these life supporting systems under pressure, it has exceeded carrying capacity.

In ‘Being the Change’ (2017), climate scientist Peter Kalmus questions whether we can sustain the amount of food we grow indefinitely into the future.

“It seems likely that global food production will be increasingly challenged by aquifer depletion, drought, heat waves, extreme weather and soil degradation. Our technology allows us to capitalise Earth’s ecological services more easily but it’s not a substitute for those services.”

Kalmus suggests that the loss of biodiversity also means that human impact has already exceeded Earth’s carrying capacity.

“Humans and livestock account for over 97% of land vertebrate mass, whereas wild animals account for less than 3%. We have essentially replaced the Earth’s wild places with agriculture, the Earth’s nonhumans with humans.

“Nonhuman animals are quite literally under relentless systematic attack from a mechanised and militarised global economy of nearly 8 billion humans; but ultimately the only way to avoid the sixth mass extinction is to address the underlying causes.”

If eight billion humans (living and eating as we’re actually living and eating today) is beyond carrying capacity, what is the sustainable limit?

Kalmus proposes that for a lower limit, it’s likely greater than one billion. At the start of the Industrial Revolution 200 years ago, when all the oil, coal and gas deposits were still underground, the human population was just under one billion. Agriculture functioned on soil, water and manure. Humans had not yet changed the atmospheric conditions, fish were still plentiful in the oceans, and extinction had not yet started its exponential rise.

A planet under pressure

This puts the Earth’s carrying capacity at more than 1 and less than 8 billion. Some evidence suggests the carrying capacity is about 4 billion. This estimate is based on the average area of land required to support one globally average person, including ecosystem services. A paper in Population and Environment (1994) suggests that the 1994 global population of 5.5 billion ‘clearly exceeded the capacity of the Earth to sustain it.’

If everyone on the planet was vegetarian, Kalmus suggests we could likely double the number of humans that could sustainably live on the planet. Because about a third of food is wasted, limiting this waste could potentially increase carrying capacity by another quarter — about one or two billion people depending on whether we are meat or vegetarian eaters – by eliminating half of this waste.

Exponential population growth in the last century has been intrinsic to intensive agriculture that involves high yielding crops, irrigation, nitrogen fertiliser and chemical pesticides. A fifth technology is now pushing yields further; genetically modified organisms. But intensive agriculture comes at a cost – with the biosphere under increasing challenge.

“The problem here is not just that our population will collapse when we’ve exceeded our ecological bounds,” says Kalmus. “It’s the risk that our totalitarian agriculture will drive the sixth mass extinction in the process, irreparably impoverishing the biosphere for the next ten million years.”

The real question about global fertility rates is not the threat to economies and society from a falling rate but the absolute imperative for the fertility rate to fall exponentially- particularly in countries with the highest carbon footprints if we are to have the remotest chance of preventing a global economy based on exponential growth — from eating the planet alive.

Rather than focusing on ways to maintain economies, we need to look beyond consumerism to search for ways that populations can live on Earth in alignment with the fantastically complex biosphere we were born into.

Dr Catherine Conlon is a public health doctor in Cork and former director of human health and nutrition, safefood.

Dr Catherine Conlon
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