The question of how many people our planet can actually support has long resonated in the fields of ecology and demography. The latest scientific analyses historical demographic data comes with a serious finding: the global human population has long exceeded the Earth's sustainable carrying capacity. Unlike other animal species, whose population size is directly limited by the regenerative resources of the environment, humans are the „ultimate ecosystem engineers.“ Thanks to human ingenuity, technological development, and the massive use of fossil fuels, we have been able to temporarily remove environmental constraints and artificially extend our population growth.

A look into history reveals a fascinating yet disturbing demographic development that can be divided into several phases. From 1800 to 1949, humanity was in a phase of so-called facilitation, which means that as the population grew, the rate of population growth increased in direct proportion.. This phenomenon was driven by technological developments and better access to resources, which improved overall living conditions and increased reproductive success.

However, this positive relationship was permanently disrupted after World War II. After a brief transitional period known as the post-war „Baby Boom“ in the 1950s, the world population entered a new, negative phase around 1962. From this moment on, the exact opposite trend applies: the more the global population grows, the more its growth rate decreases.. It is particularly important to note that the start of this decline (1962) occurred exactly eight years before the world entered a global biocapacity deficit in 1970. Since 1970, humanity has been consuming more ecological assets – such as farmland, forests and fisheries – each year than the planet can naturally regenerate.

The onset of this negative phase was not uniform across the world. Wealthier regions and areas with lower fertility rates (such as Europe and North America) experienced this turning point as early as the late 1950s and early 1960s. Conversely, regions with the lowest incomes and highest fertility rates entered this phase decades later. An extreme example is sub-Saharan Africa, which was the last region to enter the phase of declining growth rates, only entering it in 2010.

So what are the real biophysical limits of our planet? Using the phenomenological Ricker logistic model, applied to the current negative demographic phase, scientists predict that global population could reach its absolute maximum, approximately 11.66 to 12.40 billion people, between 2067 and 2076. At this number, growth would come to a complete halt, as deaths would equal births. However, this enormous number represents only the maximum carrying capacity allowed by the extreme and unsustainable depletion of natural resources.

The Earth's actual "sustainable" carrying capacity is diametrically different and, above all, much lower. Researchers have calculated that If we wanted to maintain a stable economy, minimize negative environmental impacts, and avoid overconsumption, the Earth would only be able to sustain approximately 2.35 to 2.5 billion people in the long term.. With a current population exceeding 8 billion people, the world's population is roughly 3.4 times larger than would be sustainable in terms of consumption and ecological footprint in the long term.

These demographic changes have a direct, measurable and devastating impact on our planet. The findings clearly show that the negative phase of population growth is very strongly correlated with an increase in global temperature anomalies, total greenhouse gas emissions and the global ecological footprint. Statistics even reveal that The growing population size alone explains environmental degradation and climate change even better than the increase in per capita consumption alone..

The conclusions of the published study are extremely alarming. The Earth cannot sustain our future, or even our current, population in the long term without completely and radically changing our socio-cultural practices. Current global economies, built on the illusion of constant and uninterrupted growth, completely ignore the regenerative limitations of our planet, as fossil fuels artificially cover this deficit for the time being.. For humanity to avoid catastrophic environmental collapse, it will be necessary to adopt some form of societal „slowdown“ and transition to systems that strictly respect the finite limits of land, water, energy, and biodiversity of planet Earth. JRi&CO2AI

A study published in magazine Environmental Research Letters