The Population Overshoot Factor in Ecological Economics

We were delighted by the clear consensus that emerged at the end of the Iceland conference, that population size and growth is one of the major factors in assessing the  sustainability of economies and societies, which should be taken into account. As an aid to doing so, we attach the current Overshoot Index. This is a simple extrapolation for population size from the data of the (Kenneth Boulding Award-winning) Global Footprint Network. No-one, of course, claims that the figures are precise. Indeed, by omitting non-renewables and biodiversity, they may overstate sustainable populations. But as a rough guide to orders of magnitude, not least of the scale of the overshoot problem, we believe they could be of use to ISEE members.

Signed:  Blake Alcott; Carter Dillard; Sigrun Maria Kristinsdottir; Karin Limburg; Roger Martin; Luke O’Brien; Maria Ibbarola Rivas.

To download a copy click here.

3 Responses

  1. Thank you, David, for your criticism. As one of the signers, and speaking only for myself: I agree that if ‘consensus’ means absolute unanimity we were wrong to use it, as your dissenting opinion proves. As the commonly-heard phrase ‘there is a growing consensus’ implies, though, the term is often used to mean ‘common opinion of an overwhelming majority’, but not necessarily unanimity. But I personally take your point that our phrase “clear consensus” was too strong.

    But about precisely what did we claim, and do you deny, “consensus” or overwhelming or at least large majority? This: “that population size and growth is one of the major factors in assessing the sustainability of economies and societies.” The opposite of this claim is that “population size is NOT one of the major factors…” My (con-)sense is that while there are very few ecological economists who would claim that population size plays NO ROLE, some number indeed sees its role as not “major”. In further dialogue it would be interesting to know which is your position. If it is ‘no role’ then neither the 7.5 billionth human being nor the 75 billionth matters.

    Perhaps this debate is over the relative strength of population size and the average size of throughput of each. I feel this issue is worth investigating and hope for an eventual consensus that rejects both extreme positions: ‘It’s (only) population’ and ‘It’s (only) (over-)consumption’. We should not play these factors off against each other (and also realise that each one affects the other).

    You seem to favour a third view, that the “main problem facing humanity” is “unequal distribution of income”. It is “not population size… per se”. It is however not clear whether you are focussing on the sustainability problem or the problem of justice amongst currently living human beings (or both). Our claim, as worded, was only about sustainability, i.e. justice over against other species and future humans. (Possible connections between this and unequal distribution of resources remain of course a good subject for study.)

    The historical context of our (joyful) claim is that after emphasising the effect of human numbers on environmental impact in its early years, ecological economics for a good two decades ignored it. Then, at the Leeds conference on the steady-state economy in 2010 the issue of the relevance of population size to sustainability was acknowledged in the form of a working group. At the ESEE conference in Istanbul in 2011 a session (with 3 papers) on the relevance of population size to sustainability was approved and held. An article or two appeared in the journal, and finally, at the ISEE conference in Reykjavik in 2014 a further session was held. We were frankly happy that Joan Martinez-Alier, in his parting comments at the conference, expressed his opinion that a bit more attention should once again be given to this factor.

    We concluded that the number of ecological economists willing to give this issue a place at the table is not only growing but… sizeable. If you are saying that for the SUSTAINABILITY problem “population size per se” is not a factor, I disagree. If you are saying only that it is not “one of the main” factors, we can debate: How do we define what is a ‘main’ factor, and which ones, if not human numbers, count as such?

    Yours, Blake Alcott

  2. I am always surprised when highly intelligent people, who routinely acknowledge a wide of range of problems afflicting our battered planet, nonetheless insist, when population is raised, that there is only one problem, and ‘it’s not population, it’s [consumption/distribution/capitalism/governance/externalities/bankers, etc]’. They are all problems; but only population has, for twenty years since the Cairo conference, been the subject of an irrational taboo, now happily fading.

    In Reykjavik we detected, for the first time, a wide recognition of three self-evident facts: that total human impact on the environment is, by definition, the average impact per person multiplied by the number of people; that natural resources per person are, by definition, total resources divided by the number of people; and consequently that stable or reducing populations are an essential (if far from sufficient) condition for any bio-physically sustainable economy or society. As the 2012 Royal Society report stressed, population and consumption are inseparable; and population is a multiplier of all the other problems.

    Of course the rich consume and emit more than the poor, which is why we wish to reduce both the numbers and consumption in the rich countries. It remains a fact, however, that current growth (10,000 more people per hour) will definitely stop one day, simply because a finite planet cannot sustain an infinite number of people. But it can only stop in one of two ways: either sooner, the humane way, by fewer births – family planning backed by policy to make it available and encourage people to use it; or later, the ‘natural’ Darwinian way, by more deaths – famine, disease and predation/war. Campaigners against the former are in practice campaigning for the latter. As a simple matter of intergenerational ethics, we owe it to our children to prevent this; and we are glad that most ISEE members in Iceland appeared to agree.

  3. It seems quite striking and self-serving that anyone could claim that there was a consensus coming out of the biennial ISEE meeting in Reykjavik, much less one pointing to “population size and growth … [as] one of the major factors in assessing the sustainability of economies and societies.” The wide variety of methodological and political positions expressed in the various sessions allowed any honest observer to take away from the sessions any anaysis she might want to without coming close to identifying a “consensus” position. In fact, a great many atendees insisted that the main problem facing humanity is not population size or growth rates per se, but rather the extraordinary unequal distribution of income on a global scale as well as within nations and he excessive claim on resources made by the wealthy in rich and poor nations alike.
    Considering the number of people who attended the Iceland sessions and then participated in the degrowth conference in Germany one month later, the claim by this group of colleagues offers a distinctly biased view of intellectual and political processes within the Society.


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