Human civilization is currently in overshoot, and uses the renewable resources of 1.5 earths every year. That’s an often-repeated claim in environmental circles, including on this blog. It’s a slightly tricky statement. If you don’t understand what biocapacity and overshoot are, it sounds impossible – like the athletes who ‘give 110%’.
Overshoot occurs when resources are consumed faster than they can be renewed, and when waste is created faster than it can be absorbed. You can consume more than the earth can provide in a year, but in doing so you deplete natural capital and next year the earth will be able to produce less. It’s not particularly complicated, but it’s not exactly intuitive either.
However, a new paper rejects the whole idea. It goes so far as to say that “ecological footprint measurements, as currently constructed and presented, are so misleading as to preclude their use in any serious science or policy context.” If this was from an American right wing think-tank, we’d know where to file it. But it’s not. It’s from the Breakthrough Institute and published in the PLOS Biology journal. So what’s the argument?
The ecological footprint is made up of six components – fishing grounds, built-up land, crop, grazing and forest land, and an area of land to absorb our carbon emissions. The Breakthrough Institute authors point out that of those six categories, only carbon is in overshoot. The other five are in balance or in surplus.
Since the other categories aren’t in overshoot, the whole of humanity’s overshoot is essentially carbon. “If one excludes carbon, global biocapacity exceeds the footprint of consumption by about 45%.” So, says the paper, why don’t we drop talk of ecological footprints and just talk about carbon emissions? The central conclusion is that environmentalists should go “back to the drawing board” and come up with some new metrics that make “both ecological and common sense.”
The problem with this is that it is stating the obvious to say that land use doesn’t show a deficit. How could it? You can’t farm more land than there is on the earth. Consumption can only ever be equivalent to or below biocapacity. The only one of the six categories that can show a deficit is carbon.
The other categories still matter, because it is our total land use that determines whether or not we are in overshoot. If we didn’t use so much land for grazing and crops, there would be more forest to absorb our carbon.
The Breakthrough Institute also argue that summarising sustainability into a single headline figure may be a fool’s errand. “A set of indicators, each pertaining to an identifiable and quantifiable form of natural capital or ecosystem service, is likely to be more comprehensible and useful than a single aggregate index.” That’s true, in the same way that GDP is a very blunt instrument in measuring economic progress. But that doesn’t mean we should ditch ecological footprinting, or GDP for that matter – only that we should not privilege one metric above all others. It would certainly be rather rash to abandon footprinting techniques without any obvious alternative. It’s probably the most useful shorthand measure of sustainability at our disposal, however limited it may be.
So I’m not sure the Breakthrough Institute’s main criticism is valid, and I think they overstate their case considerably in suggesting that ecological footprinting has no place in science or policy. But the paper does highlight an ongoing problem in sustainability circles – our metrics are still confusing and over-complicated.
One of my enduring frustrations in writing about sustainability is the convoluted nature of its terms. ‘Carbon footprint’ is a complete mess of a metaphor – how can you have a footprint of gas? I imagine most people think of footprints as a trail left behind us rather than our shoe size. Expressing quantities of gas in tonnes is counter-intuitive too, and in acres of land even more so. Then you get carbon, CO2 and CO2e to content with, which are often used inter-changeably but are not the same. It’s hardly surprising that many people aren’t entirely sure what’s going on, and that the unconvinced remain so.
I intend to carry on using the concept of ecological footprints for the time being, but I share the Breakthrough Institute’s hopes that somebody, somewhere, is working on something clearer and simpler.