Calculating a Sustainable Population Size
This peer-reviewed paper is summarised in this article Population growth has contributed 80% of ecological overshoot. The article concludes that humanity cannot achieve genuine sustainability without reducing our global economy and our population size to less than a quarter of today’s levels. This webpage helps the lay person to understand why the global human population needs to shrink so much to become genuinely sustainable. This article from the excellent Mother Pelican Journal offers links to a lot of relevant research. Optimum Population Size
The data held by the Global Footprint Network reflects the estimated exploitation of the biocapacity available on Earth by humans. Their data informs us that humans are using about 1.75 of Earth’s biocapacity, see image above. We are not allowing any spare biocapacity for other life forms. The book Half Earth, by the biologist E O Wilson, suggests that for biodiversity to flourish, we need to restrict our global demands to about 0.5 of Earth’s biocapacity. We can use this suggestion as a guide to the carrying-capacity of Earth for a human population.
The biocapacity of Earth is measured in global hectares; this reflects the number of productive hectares on Earth. Nowadays, this figure diminishes from year to year because of deforestation and desertification. The figure is roughly 12 billion global hectares. Therefore a sustainable global population would need to limit itself to about half that figure; this would leave us 6 billion global hectares. There is a helpful research paper that suggests that 2.14 global hectares provides adequate resources for a fulfilled human life. If we simplify the calculation by assuming that we can subsist happily using 2 global hectares per person, we can draw the conclusion that by minimising our consumption per capita, Earth could support about 3 billion people by sharing these 6 billion global hectares fairly amongst us.
Therefore, to return within the carrying capacity of Earth we need to aim for a global population of less than 3 billion, and a footprint per capita of about 2 global hectares per person. I describe how we might do this peacefully in my unpublished science paper, The Roadmap to Ecological Justice. Some of the ideas are summarised in my article Demystifying Degrowth.
The Global Aspiration for Ecological Justice lies at the heart of the suggestions in my science paper. All of my articles on Medium and LinkedIn are intended to promote the mindset that is required to peacefully embrace such a radical idea. This two minute video provides a very brief overview. If you like the idea you can sign the petition.
The UK operates at about four times the available biocapacity. If the UK was to shrink its footprint by 75% this still allows no biocapacity for other life forms.
