No, Virginia, there isn’t a Santa Claus. Yes, climate deniers, human industry can and does affect earth’s natural systems. And yes, growth proponents, there is such a thing as overpopulation. While I have yet to encounter anyone who disagrees with this notion when presented with a small scale example (i.e. only so many people can live in any given apartment building), many of those same folks balk at the idea that earth itself has a holding capacity. Or a productive limit. The thinking seems to be that there will always be some new parcel of land to cultivate (there won’t), or that technological developments such as bioengineered agriculture or vertical farming will negate the need for more land (they won’t). The simple and incontrovertible truth lies in the most basic of economic models, which in turn has become the most fundamental of sustainability relationships: supply and demand. Finite resources cannot sustain infinite growth.
This is a topic I’m going to come back to repeatedly, but for now I want to share some info from the website of the UK-based Optimum Population Trust. I’ll preface it, however, by saying that the debate surrounding overpopulation has two distinct phases. The first, which itself can be divided into dozens of phases, consists of determining just how many people the planet can comfortably support. The second revolves around the myriad ways in which that number can be achieved. The first is mathematical, built on models of supply and demand. The second is much more complex and controversial, with profound political and social implications, and is many ways shaped by the conclusions of the first. So, like the song says, let us start at the very beginning. It’s a very good place to start.
Optimum Population Trust
Defining an optimum population
An ‘optimum’ population, in dictionary terms, is the ‘best or most favourable’ population. But a dictionary cannot tell the whole story. Best for what purpose, and best according to which criteria? For OPT, a green think tank, an optimum population means, at its simplest, a population size which is environmentally sustainable in the long term, affords people a good quality of life, has adequate renewable and non-renewable resources necessary for its long-term survival and consumes or recycles them to ensure it will not compromise the long-term survival of its progeny.
Few would argue with the statement that ‘population cannot continue to increase indefinitely’. But how do we define the limit? Using a tool called Ecological Footprinting*, which provides a snapshot of human ecological impact under given circumstances, it is possible to throw some light on this question.
(* Ecological footprinting data given in this paper have been taken from Global Footprinting Network research published in the WWF Living Planet Report 2006, using 2003 data.)
A sustainable population for Earth
- Assuming the global biocapacity and average footprint [F1] remain stable at the 2003 level, then, to become sustainable, the world population needs to contract to a maximum of 5.1 billion.
- For a ‘modest’ world footprint of 3.3 gha/cap (without allowances for biodiversity or change of biocapacity), the sustainable population is 3.4 billion.
- For a ‘modest’ world footprint of 3.3 gha/cap, plus a 12% allowance for biodiversity (but none for attrition of biocapacity), the sustainable population is 3.0 billion.
- For a ‘modest’ world footprint of 3.3 gha/cap, plus a 20% margin for biodiversity and attrition of biocapacity then the sustainable population is 2.7 billion.