Eco Basics

[This is the third part of my introduction to ecological thinking, Ecology 101. The photo was taken on the NSW south coast.]

ECO-BASICS: I = PAT, Carrying Capacity, Overshoot, Ecological Footprints, Ecological Justice

Ecologist Paul Ehrlich proposed the following IPAT formula for measuring any human ecological impact:

I(mpact) = (P)opulation x (A)ffluence x (T)echnology

Where P = the population number
A = affluence (in the strictly measurable sense of resource consumption per person or ‘ecological footprint’)
T = the technology used to provide that resource consumption


Although Ehrlich is known mainly for emphasizing the overpopulation issue, the I=PAT formula in fact provides an important refutation of any one-sided (‘Malthusian’) emphasis of overpopulation and mere population numbers as the main cause of the global eco-crisis. The formula actually shows how ecological impact is not a matter of sheer numbers of people but of how much these people directly and indirectly consume, their ‘ecological footprint’, and of what kinds of technologies they use to do so.

Thus, for example, a small, affluent population directly or indirectly consuming a lot of resources with wasteful and polluting, energy-intensive technologies (like us) will have a far greater ecological impact than a large, non-affluent population consuming little with simple, less energy-intensive technologies.

This is in fact how things really are in our inequitable world with regard to rich and poor countries: per capita resource consumption is immeasurably larger in rich, industrialised countries than in the poorer, less industrialised countries with larger populations.

One child born in a rich country (or to rich parents in a poor one) may have a total ecological impact or footprint during its lifetime that may, on average, be 10-100 times greater than that of a child born in a poor country. Almost daily meat eating, cars, disposables, frequent flying, energy-intensive foods, goods and lifestyles ‒ all of these exclusive prerogatives of the globally affluent have huge ecological footprints. In these global ecological terms, it is not the poor, but the rich countries and classes which are ‘overpopulated’. It is the rich who are killing the earth.

Locally, of course, there may be overpopulation in different parts of poor countries when local resources and biota are over-consumed. This has to do with the important notion of ecological carrying capacity, i.e. the biological limits of any ecosystem for the communities of organisms within that ecosystem.

Any system can support only so many organisms with a certain level of impact on the system as a whole. If the numbers of organisms, or communities of organisms, and their total cumulative impacts increase beyond (‘overshoot’) this critical point of maximum carrying capacity, the system will be severely stressed and disturbed. If it then cannot at some point regain its previous level of functioning or dynamic equilibrium, it will ultimately collapse into another, less complex state. It will be in ‘overshoot’. A paddock or savannah system, for example, can only support a certain number of stationary herbivores like cattle, sheep, goats or deer before it is overgrazed and then degrades and ultimately turns into an eroded, arid wasteland or desert.

Like many a local civilization before it (e.g. Mesopotamian, Roman, Mayan), our global civilization as a whole has been in ‘overshoot’ since perhaps the 1980s, i.e. human resource consumption and technological use has gone beyond the earth’s carrying capacity.

We are now consuming roughly ‘one and a half earths’, clearly a situation of ‘ecological debt’ or ‘overdraft’ that cannot long continue without massive disturbances and collapses of ecosystems and mass species extinctions (as is happening). As a species we are living unsustainably beyond our means, living off the earth’s natural ‘capital’, not its ongoing ‘income’, and thus destroying the very life support systems that make human civilization possible.

Rich people’s and countries’ ecological debt is not just a present one. Climate chaos, for example, is due to the immense amount of greenhouse gases released by fossil-fuelled economic growth in the rich industrialised countries in past and present. Both in historical aggregate and per capita, the carbon emissions debt of the rich countries and classes is immeasurably higher than those of the poor countries and classes, which will in many cases be experiencing more suffering as a result of climate chaos.

This is not fair. The ethical notions of ‘climate justice’ and ‘ecological justice’ thus mean that the rich should be paying back their ecological debt by compensating the poor, redistributing wealth and land and transferring wealth by funding ecologically sustainable development to eradicate poverty and the transition to more equitable, lower-energy societies. Ecological justice is inseparable from social justice in the sense of greater equality and wealth redistribution.

Also, since the economic pie can no longer grow without destroying the earth’s life support systems, the economic pie has to be redistributed. This is why ecology and ecological limits have such socially radical implications.


~ by Peter Lach-Newinsky on August 15, 2012.

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