Shrinking the Footprint Ecotheology of human fertility and population

17 July 2013

Danny Dorling, Population 10 Billion

Filed under: Reviews — John @ 5:14 pm

Dorling-10Billion-coverReview in progress of the new book by Danny Dorling, Professor of Human Geography, University of Sheffield.

Population 10 Billion : The Coming Demographic Crisis And How To Survive It (London: Constable, 2013)

I heard Danny Dorling speak (on the UK census) at a Population Studies (BSPS) conference in Nottingham in 2012. After many successful academic books he ventures this polemical book to calm readers’ worries about population (he is especially reacting to Stephen Emmott’s recent book which also has “10 Billion” in its title). Dorling’s book is wide-ranging, sweeping across many disciplines. I understand his wish to steer a “possibilist” path between optimists and “angry pessimists” but there are parts where his ideas are close to cornucopian optimism and I begin to critique those below.

Dorling claims “it is consumption, not population, that matters” (123). This is not a throwaway line: he spends more than a page trying to justify the idea. Dorling suggests that “some extra people can teach others to consume less and hence reduce consumption overall, even as population rises” (125). I accept that given a rising population at some level consumption per person will start declining, but his idea that total consumption by humankind could shrink (voluntarily in a non-catastrophic situation) while population grows is speculative.

Dorling’s optimism regarding the future cannot be falsified, but he also suggests that population is not a multiplier of consumption, and he claims it is “not true that human environmental impact on the planet is a product of the number of humans” (124). This can be tested. There has been research since the 1990s seeking to quantify the relationship between population size and ecological impact in terms of “elasticity” which varies regionally.

For example an elasticity of 1.0 (unity) indicates that a 1% increase in population causes a 1% increase in impact. Above 1 means the effect is more than proportional. How could that be? John Harte (2007) argued that elasticity may worsen as population rises due to nonlinear thresholds, for example farming expanding on to marginal land. Conversely, below 1 means it is less than proportional. For example in a densely populated area well organised transport may be more efficient, as is high-density housing.

Most studies are limited to greenhouse gas emissions, rather than the much broader “ecological footprint” (GFN), but even so they are worth considering. A meta-survey by Liddle (2012) found a range of results for elasticity from 0.69 to over 2. A study by Dietz and Rosa (1997) calculated a global average elasticity (with regional variations) of 1.15 – so a 1% increase in population causes 1.15% more emissions. Anqing Shi (2003) found a global elasticity of 1.42. Theoretically the same principle can be applied to population shrinkage: what reduction of impact would it deliver? For the USA, Michael Dalton (2008: 90) found that the “effect of smaller population size on emissions is somewhat more than proportional.”

Though proportionality for the broader measure of ecological footprint is less well established, I think it is safe to say that impact is roughly proportional to population. I accept that for urban areas proportionality could be less than 1, but that still means a larger population has a larger impact, just not in a 1:1 proportionality. Dorling by contrast is claiming that there is no relation, and even that total impact could be less with more people. That would require a negative elasticity, and that is well outside the range observed in any research.

Dorling rightly critiques the idea that population is limited by living-space, noting that even among non-human species, for example bats, numbers are not limited by roosting space (131). Cornucopian writers often rehearse the (defective) argument that suburban homes for the global population could all fit into Texas, so we have plenty more space. By contrast, even old-fashioned “carrying capacity” ideas were about food (e.g. based on grazing regrowth for livestock) not accommodation, and the capacity calculation used by people concerned about population size today is not living-space, but the ecological footprint.

P.S. This is provisional as I have not yet finished reading the book!

John McKeown

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