When the entire world shut down during the COVID-19 pandemic, humanity was forced into isolation. However, a surprising yet endearing narrative claimed that ‘nature is healing’. With better Air Quality Index (AQI) and increased sightings of rare animal and bird species worldwide, nature reclaimed the “empty spaces” left by the now-isolated humans. Amanda Bates et al (2020) viewed these major lockdowns as a ‘Global Human Confinement Experiment’, which would have been impossible to conduct hitherto. A “hiccup” to human history was now seen as a "breather" in ecological history.

It’s easy to conclude that humankind’s unjust occupancy of space began when the human population surged post-industrialization with better living conditions, a growing birth rate, and age expectancy. The harder part is understanding when we crossed the population threshold, and what constitutes an optimal human population.

Human activities jeopardize other species

First, an optimal human population must address the unequal living conditions of people globally, which necessitates addressing the existing Global North and Global South demarcations. In the global South, countries often bear the brunt of environmental exploitation and climate change despite contributing the least to these problems. This is evident in the widespread deforestation in the Amazon jungle and rising sea levels that threaten the existence of low-lying island nations. Similarly, in the global North, environmental racism leads to hazardous waste and polluting industries being placed disproportionately in minority and disadvantaged communities (Dawson, 2017).

From an ecological perspective, it’s crucial to assess the Earth's carrying capacity and recognize that humans are not the planet's sole inhabitants. This refers to the maximum population size an environment can sustain indefinitely with available resources. The Global Footprint Network estimates humanity uses 1.7 Earths to meet our resource and waste needs.

The decline in bee populations exemplifies how human activities jeopardize other species and ultimately human survival. The United Nations Food and Agriculture Organization (FAO) reports that pollinators affect 35% of global agricultural land, supporting the production of 87 of the leading food crops worldwide, and yet pesticide use, habitat destruction, and climate change have led to a decline in bee populations. The collapse of the Atlantic cod fishery off the coast of Newfoundland, Canada, in the early 1990s is another prime example. What was once a thriving industry, collapsed due to overfishing, illustrating the long-term impacts of unsustainable practices.

Seeing humans as the earth’s primary inhabitant has led to policies and practices that prioritize short-term economic gains over long-term ecological sustainability. Recognizing our role within a broader ecological system is key to developing strategies that respect the Earth's carrying capacity. Johan Rockström’s concept of 'planetary boundaries' outlines nine thresholds, like climate change and biodiversity loss, that shouldn't be crossed to maintain a 'safe space for humanity’. Conservation efforts, such as the establishment of protected areas and the restoration of degraded ecosystems, using renewable energy sources, play a crucial role in preserving biodiversity. Yet, as the population grows, a sustainable utopian future feels increasingly like a fantasy. 

What is the optimal human population?

But can an optimal human population even be calculated? Quantifying the optimal human population involves establishing parameters that balance the needs of humans with the sustainable use of Earth's resources. While exact numbers are challenging to pinpoint,  adopting certain models can provide a framework for determining and achieving this balance like the ‘Ecological Footprint’ metric, which helps measure how much biologically productive land and water area a population requires to produce the resources it consumes and to absorb its carbon emissions. On the other hand, The 'natural capital' viewpoint values Earth's assets like soil and water, encouraging sustainable use by integrating them into economic systems.

Moreover, applying cost-benefit analysis to these population policies can help establish optimal population levels.  For example, investing in family planning and education has been shown to reduce fertility rates. (Martin, 1995). A study by the Copenhagen Consensus Center found that every dollar spent on family planning programs yields significant economic returns by reducing the need for government expenditure on health care and education, and by increasing women's participation in the labor force (2020). Second, urban planning and development can help design cities to maximize efficiency and minimize environmental impact through sustainable infrastructure, green spaces, and public transportation systems. International cooperation and equitable resource distribution are essential for achieving optimal global population levels. Here, wealthier nations can support sustainable development in poorer regions through investments in technology, infrastructure, and education.

The optimal human population could just as well be 8.1 billion—the current global population—if sustainable practices and an equitable attitude towards all species and resources are integrated into daily life worldwide. However, even with just 1 billion people, unsustainable practices could still cause severe environmental harm. The optimal human population is therefore not just a quantifiable entity, but how those people live and manage the available resources.

(The writer is Shiv Nijhawan ; a Grade XI student at  The Shri Ram School Moulsari -India. Views are personal. He can be reached at nijhawanshiv008@gmail.com; Linkedin: shiv-nijhawan)