Population growth has contributed 80% of ecological overshoot

By Philip Cafaro | 30 November 2022
The Overpopulation Project

(Photo by Julien Gaud on Unsplash)

William Rees is the originator of ecological footprint analysis, the influential approach to measuring sustainability. In a new article, he argues that humanity is deep into ecological overshoot and that we need to ratchet back our numbers and the size of our economies before nature does it for us.

William Rees has been a leading sustainability scholar for three decades. In a recently published article, The human eco-predicament: Overshoot and the population conundrum, Bill makes three interlocking claims:

The human enterprise is in overshoot, depleting essential ecosystems faster than they can regenerate and polluting the ecosphere beyond nature’s assimilative capacity.

Mainstream approaches to alleviating various symptoms of overshoot merely reinforce the status quo.

The continuity of civilisation will require a cooperative, planned contraction of both the material economy and human populations, beginning with a transformation of the fundamental values … underpinning neoliberal capitalist industrial society.

How big a contraction? Rees estimates a sustainable global population at 1 to 2 billion people—provided citizens in wealthy nations are willing to reduce our individual ecofootprints to 25% their current size. But as he notes, “in the real world … the population is still growing and there is zero international interest in sizing the global economy to fit within carrying capacity or to share the world’s bounty more equitably.” While “zero interest” might be an exaggeration, it’s hard not to share his pessimism about such ideas going mainstream anytime soon.

For followers of this blog, perhaps the most interesting part of the paper is a section which argues that “while overconsumption and population growth have long been recognised as co-drivers of overshoot, population growth is currently the major contributor to total consumption growth and associated negative ecological impacts” throughout the world. Comparing changes in per capita ecofootprints and changes in population for all the world’s nations between 1960 and 2016, Rees finds that population growth has been the dominant driver in increased national ecofootprints for all four of the World Bank’s country groupings based on national income (see figure below).

Changes in ecological footprint, biocapacity and population for nations in the World Bank’s four average income brackets, 1961–2016. Source: William Rees, The human eco-predicament: Overshoot and the population conundrum. Vienna Yearbook of Population Research 21 (2023): 1–19.

It comes as no surprise that in low-income countries, with rapidly growing populations, population growth accounted for 100% of the growth in (still relatively small) national ecological footprints between 1960 and 2016. But it also accounted for 88%, 73% and 75% of the growth in ecofootprints during that same time for lower middle-income, upper middle-income, and high-income countries, respectively (see section 3 in Rees’ paper for more numbers and calculations).

Globally, according to Rees, “population growth accounted for 80% of the increase in the total human ecological footprint above what would have accrued had populations remained constant while income/consumption and per capita EFs increased” after 1960. Next time a friend tells you that “the problem’s consumption, not population,” you might want to send them the paper!

Rees is quick to remind readers that citizens of high-income countries make much greater per capita demands on nature than those in poorer countries, noting that “1.14 billion rich consumers (15% of the human population) lay claim to 57% of global biocapacity.” He criticizes an “egregious, inexcusable, yet still increasing material inequality between rich and poor people and nations in today’s world.” And he states: “globalisation and unfair terms of trade in world markets enable the citizens of wealthy countries to appropriate legally, by commercial means, several times their equitable share of Earth’s biocapacity from other countries and the global commons.”

Here Rees may be falling into what Gaia Baracetti calls the per capita fallacy: the view that many smaller ecological footprints are more virtuous than fewer, larger ones. After all, it isn’t clear that all differences in individual or national wealth are the result of injustice, or that absolute equality in wealth or resource use is demanded by justice. Poor people around the world want more consumption and wealth, and with the UN’s Sustainable Development Goals, the international community has committed to helping them achieve that. But this will inevitably increase demands on the biosphere, which is already overused by people.

While Rees stresses that population decline in rich countries would generate more ecological benefit than in poor countries, he observes that “the most significant social benefits from stable populations would accrue at the micro level to the low-income families of poor countries who would enjoy larger slices of the economic pie.” But he fails to mention that a four-fold increase in their populations since 1960 has given them smaller slices of the pie, contributing more than “unfair terms of trade” to today’s inequalities. He states that “Egregious and widening inequality is a separate socio-political problem.” But it is not separate, it is fundamentally linked to the diverging demographics of rich and poor countries. The main factor separating today’s emerging economies (e.g. in Southeastern Asia) from the least-developed countries was their success in lowering birth rates four decades ago. We must stop seeing the population issue as separate from, or even a distraction from inequalities, and start seeing it as instrumental in closing the gap.

Despite these caveats, Bill Rees may be right that any successful effort to achieve global ecological sustainability must find a way to distribute resources and share Earth’s limited assimilative capacities more fairly within and among societies. He makes a strong case that this also must involve decreasing human numbers and, for many of us, our personal demands on the natural world.

Reprinted with permission from Frank Götmark – Project leader of The Overpopulation Project (TORP); Professor, Animal ecology and Conservation Biology, University of Gothenburg.

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