Declining Births: Demographic Catastrophe or Natural Evolution?

A Global Phenomenon with Deep Roots

Since the beginning of the 21st century, most developed countries and an increasing number of emerging countries have faced a continuous decline in birth rates. The global fertility rate has dropped from 5 children per woman in the 1960s to less than 2.5 today, with regions like Europe, East Asia, or North America falling below the generational renewal threshold (2.1 children per woman). This phenomenon, far from being cyclical, is rooted in structural transformations: urbanization, women's empowerment, cost of raising children, career prioritization, and changing personal aspirations.

Fertility Rates by Country: Demography in Decline

Demographic Drift or Systemic Adaptation?

Is the decline in births a dysfunction or a transition towards a new state of equilibrium? From a systemic perspective, human societies tend to stabilize around demographic equilibria when environmental, economic, and social pressures demand it. Japan, often seen as a demographic laboratory, shows that a society can continue to function despite a decrease in its population (at the cost of profound adjustments: robotization, selective immigration, reorganization of social services).

Economic Implications and Intergenerational Dynamics

The main challenge posed by this transition is the imbalance between workers and retirees, with an increasing dependency ratio. This results in pressure on pension and healthcare systems and a reconfiguration of production. However, the decrease in the number of children reduces educational investments and potentially opens margins to improve their quality. The notion of an inverse demographic dividend emerges, with the hope that fewer but better-educated generations will support increasingly technological economies.

A Civilizational Paradigm Shift?

The demographic transition questions the very notion of progress, long associated with continuous growth. Through an anthropological lens, it can be seen as a form of adaptation to a constrained biosphere. Fewer humans, better equipped, more connected: a hypothesis that some demographers qualify as cognitive convergence. Human history has never been linear, and this "silent crisis" could be a natural long-term adjustment comparable to phase transitions in statistical physics.

Towards a Society of Quality Rather Than Quantity?

Rather than a collapse, the decline in births could mark a shift towards controlled demography. This requires rethinking our institutions, growth models, and intergenerational contracts. Far from panic, it would involve a smooth reorganization, as a complex system would do in a transition phase. In this sense, the decline in births, far from being an anomaly, could well be a thermodynamic adjustment towards a more resilient society.

Demographic Catastrophe: When the System Declines Faster Than It Adapts

Source: World Bank – Indicator SP.DYN.TFRT.IN and United Nations, World Population Prospects 2024.

Limit of Socio-Economic Self-Regulation Capacities

While the decline in birth rates may appear to be an adaptive response to global constraints (resources, overpopulation, climate), it can also represent a risk of systemic destabilization when the speed of change exceeds the self-regulation capacities of the socio-economic system. In terms of system dynamics, this is referred to as exceeding the response time of positive or negative feedback loops.

Snowball Effect and Demographic Inertia

In countries with very low fertility rates (≤ 1.3), such as South Korea or Japan, a spiral of decline is triggered: fewer births ⇒ fewer young adults ⇒ fewer future births, in a snowball effect. This inertia, described by the notion of population momentum, makes it practically impossible to return to a replacement level, even if fertility rates were to suddenly rise.

Loss of Dynamic Entropy and Systemic Contraction

From an energy perspective, such a system enters a phase of demographic contraction not compensated by external input (immigration or massive productivity gains). This situation can be modeled by a loss of dynamic entropy: the system loses its diversity, its capacity for innovation, its resilience. The number of brains, arms, producers, and consumers declines, leading to a decrease in economic activity, fiscal contraction, a gradual collapse of social infrastructures, and rising intergenerational tensions.

The "Low Fertility Trap" and Critical Phase Transition

This scenario, described by some demographers as the "low fertility trap", could become as perilous as that of unchecked overpopulation. In the physics of complex systems, this is akin to a critical phase transition without a stable attractor. If no adjustment mechanism (technological, political, migratory, or cultural) takes over, the decline in births could lead to an irreversible demographic collapse in certain regions of the world.

The Paradox of Biological Growth Control

The paradox is as follows: humanity has finally mastered its biological growth, but if it reduces it too quickly without adapting its structures, it risks a sudden loss of organization, a kind of demographic entropic crisis. The demographic entropic crisis, a concept that can be defined as an irreversible loss of complexity in the human system due to rapid and prolonged population decline, can generate a series of systemic catastrophes.

Demographic Entropic Crisis as a Catastrophic Bifurcation

• Collapse of human capital: Examples (disappearance of rare professions, shortage of doctors, engineers, teachers, or specialized technicians).
• Destabilization of pension and healthcare systems: Bankruptcy of social systems, impoverishment of the elderly, and widespread health crisis.
• Self-sustaining economic shrinkage: Serial bankruptcies, GDP contraction, loss of critical scale for innovation or R&D investment.
• Geopolitical crises and intergenerational conflicts: Social tension, tax rejection, institutional instability.
• Loss of technological sovereignty: Decline of critical infrastructures (energy, defense, digital), strategic vulnerability against younger demographic blocs.
• Implosion of cities and territorial disintegration: Geographic contraction, abandonment of public services, urban wastelands, rural desertification.
• Slow cultural extinction: Reduction of cultural complexity, global homogenization, loss of diversity, weakening of collective meaning, increase in nihilism or identity withdrawal.

When will the global population reach its peak?

• Estimated peak date (UN median scenario): around 2086, with approximately 10.4 billion inhabitants.
• UN low scenario: decline starting in 2060, maximum < 9.5 billion