Sustainable global population would be around 2.5 billion people — 5.8 billion less than the current population. 20th century expansion was artificial and only delayed the inevitable, new research suggests.
The human population has already exceeded the planet’s capacity to sustain it on a lasting basis at current levels of consumption.
The conclusion is from a March 26 study in Environmental Research Letters. In it, researchers warn of an increasing imbalance between the pressure exerted by humanity and the capacity of natural systems to regenerate.
The research, led by Corey Bradshawfrom Flinders University, in Australia, concludes that the Earth is being pushed beyond its ecological limits and that, without profound changes, the current growth model could worsen global instability in the coming decades.
The work is unprecedented: it is the first to investigate the relationships between the rate of population variation per capita and the long-term average population size, according to , and uses more than 200 years of demographic data to estimate what ecologists call “carrying capacity”: the number of individuals of a given species that an environment can sustain in the long term, taking into account available resources and the speed at which these resources are renewed.
In the case of the human species, this account becomes particularly complex, since the A wise man has managed to circumvent many natural limits through technology, especially using fossil fuels.
According to the authors, it was precisely access to these energy sources that enabled the acceleration of population growth throughout the 20th century. The use of coal, oil and gas has allowed food production, transportation, industry and consumption patterns to expand, creating the illusion that the planet’s capacity could continue to increase indefinitely. But This expansion, in the researchers’ view, was artificial: instead of resolving ecological limits, it postponed them at the cost of growing environmental debt.
But the study distinguishes between two concepts. On the one hand, the “maximum load capacity”that is, the absolute limit that the Earth could support — regardless of associated human costs, such as famine, war, or disease. On the other, the “optimal load capacity”understood as a population level that is simultaneously sustainable and compatible with a minimum standard of well-being.
It is in this second measure that the most alarming conclusion of the investigation emerges: at the current level of resource consumption, the sustainable global population would be around 2.5 billion people (The current world population is around 8.3 billion).
I and maximum capacity calculated by the authors is around 12 billion, a number that can be reached between the end of the 2060s and the 2070sif current trends continue. It is a frightening limit, associated with great social and ecological pressures.
The analysis also shows how global demographic dynamics entered a new phase from the beginning of the 1960s. Until the mid-20th century, population growth was associated with an acceleration in the population growth rate, but this pattern began to reverse: the population continued to grow, but at a proportionally slower pace. The authors describe this phenomenon as a “negative demographic phase”where adding more people no longer translates into faster and faster growth.
The difference between the number considered optimal and the effective population helps, says the investigation, to explain several of the current environmental crises. Science Alert recalls, for example, that pressure on water resources has intensified to the point where international organizations are warning of a situation of strong global imbalance. And numerous animal populations are in decline, unable to compete with humans for access to territory, food and water.
Dependence on industrial fertilizers, energy-intensive logistics chains and lifestyles based on fossil fuels has temporarily expanded the Earth’s carrying capacity, but is also accelerating the degradation of life-sustaining systems, according to the study.
In this context, although the public debate often focuses on excessive consumption per person, the authors maintain that variables such as The global temperature anomaly, ecological footprint and total emissions are better explained by the increase in the total number of people than by growth in per capita consumption alone.
Limitations of the investigation
Despite everything, it is also necessary to remind readers that consumption is uneven across the globe: any discussion about population control could be dominated by discriminatory political discourse, the authors predict.
The study also has methodological limitations. There are too many variables influencing population evolution, growth rates and resource availability to be able to capture the full complexity of the Earth system. The numbers presented should be understood as approximations supported by available data, and not as absolute predictions.
Still, the message is clear: the planet is already under severe pressure and the room for maneuver is shrinking.
