Saturday, July 08, 2006

Ecological footprint and One Planet Living - is it complete nonsense?

Perhaps I've got this all wrong... do tell me if I have.

There's much excitement about "One planet living" and the concept of an "ecological footprint". WWF has popularised it and David Miliband blogs his enthusiasm. The idea is to convert all the various impacts on the environment to 'global hectares' (gha), the area of productive land required to grow food, extract minerals, manufacture things, build houses, dispose of wastes and absorb emissions for each person. This is then compared to the actually available productive land area per capita. The ecological footprint of the UK is thus determined to be 5.4 global hectares per person (gha/cap) compared with a world average of 2.2 and an available global capacity
of 1.8. So here in the UK, we are Three Planet Living or thereabouts.

Given the heady excitement surrounding the idea, I thought I ought to be up to speed. And now I am, I fear the idea is pure nonsense. A few comments:

  • The trouble is in the conversion factor for carbon emissions to forested land area needed to absorb the carbon. Land or trees don't absorb much carbon - the overstretched carbon cycle does. Suppose there was enough land available to plant enough trees, we'd be happily One Planet Living, except our carbon cycle would still be 4-5 times overused. The degree of excessive use of the carbon cycle is independent of the available productive land area and so using the latter to characterise the former is nonsense.
  • What if the carbon was sequestered in deep oceans or pumped into abandoned oil or gas wells? The actual land area might be very small. The choice of forests to be the mode of sequestration is arbitarary and numbers based on this assumption are nonsense.
  • Land area and forests are 'stocks' and carbon 'reservoirs'. Emissions, however, are a 'flow' or carbon 'source'. Forests are carbon 'sinks' only while growing and once mature they stop absorbing. It is wrong to compare them in this way - and the point is conceded in the rare places where the methodology is explained*. You just can't compare stocks and flows like that - it's nonsense.
  • How much we modify the climate is a question of the risks we are prepared to take (or impose on future generations). I'd prefer much less risk, but to pretend that all carbon needs to be sequestered is nonsense.
* I stuggled to find any discussion of the factors used to convert energy to land area on the many pages of reports and webs sites on this stuff. Eventually tracked it down to page 22 of this (note how caveated this is). In most of the reports there is nothing that tells the reader what is being done - very poor show.


Chris Yiu said...

Clive - I think the basis of your argument is correct: the selection of carbon sequestration mechanism is arbitrary, and there is a logical flaw in comparing the annual flow of carbon with the stock of land required to absorb it.

It seems to me there are two other points being made: (1) the average UK citizen's ecological footprint is larger than the average for the global population, and (2) the global average is higher than global capacity.

(1) is really a distributional question. And a situation in which everyone carried the same footprint might not be welfare optimising.

(2) is pretty meaningless as a piece of static analysis. It's the future paths of consumption and resource availability that matter. And even then like you say there's a judgement about how we value current welfare vs that of future generations.

This doesn't mean OPL is complete nonsense - just that we need to recognise it's limits. What's been exposed is the tradeoff between intellectual integrity and simple messages that people (and policymakers?) can understand.

Clive Bates said...

Hi Chris... agree that the comms idea is basically pretty good. And does apply to emissions etc. But I think important for trust and credibility that the narrative strapline doesn't become the analysis.