Note: I haven't forgotten about my promised followup to my article on Julian Simon, it will appear after this one.
Two people have commented on my article on the recent paper from the Optimum Population Trust, namely Martin Desvaux, the paper's author, and Tim Worstall, the blogger with an interest in economics, who's also been critical of Desvaux's paper.
The question at issue is whether technology increases or decreases humanity's impact on the environment and whether T in the I=PAT equation should be considered to be a multiplicative term or whether we should divide bed T. Note that I measures the human impact on the environment, P is the population and A is a measure of consumption (or affluence).
I have thus far sided with Tim Worstall's view that technology helps us reduce our impact on the environment, however whilst Devaux acknowledges that technology can do so, he argues that overall it has been a driver in increasing humanity's impact on the environment. From his comment:
I think it is safe to state that, since the industrial revolution, technology has enabled us to reduce infant mortality, increase food production and increase life expectancy, all of which have caused the largest population explosion in the history of humankind. I think we can also safely assume that in that arena T is greater than 1 as a result. Such progress was possible only because we could extract oil, coal and gas out of the ground in ever increasing quantities, transport it via road, rail, pipe and sea* all around the world which, I feel sure you will agree, has also had a T-greater-than-one impact on the environment. In addition, we get most of our fertilizers from hydrocarbon technology. Without fossil fuels and thereby electrical energy, medical advances would have been impossible, We would not have been able to develop (to mention those which immediately spring to mind): warm homes, fridges, leisure centres Olympic stadia, moon shots, as well as several billions of cars, millions of lorries, ships buses, railways, aircraft, agricultural machinery factories, processing plant …. with all the infrastructure of roads, ports, depots, etc that these entities require.What Devaux is saying here is that the advances in technology associated with the industrial revolution and the fossil fuel economy have led to a huge increase in both population and affluence, which has led to an increase in humanity's impact on the environment, and thus we should consider T to be a multiplicative variable, with value greater than 1 in the I=PAT equation.
I think this is a misunderstanding of the role of T in the equation. Suppose we rewrite the equation to give us T in terms of the other three variables. We then get T=I/(PA). T is thus measuring the environmental impact per unit of consumption, where A is consumption per head of population and P is the size of the population. Stated in these terms, we can see that T does not measure "technology" per se (as I argued here) but rather measures a variable which technology can influence.
As Tim Worstall points out, Desvaux is double counting. Desvaux suggests that technological changes drove an increase in population and an increase in affluence, thus implying T should have a value > 1. The problem is that in the I=PAT equation, P and A already reflect those increases, thus to incorporate those increases in the value of T involves incorporating them twice!
This illustrates a weakness of the I=PAT equation. It treats P, A and T as independent variables when in fact there are feedbacks between them. But Desvaux is surely correct that technological advance enabled the large human population we now have and the levels of affluence we now see, and as I pointed out earlier, increases in affluence have led to a fall in birth rates in developed countries (and increasingly elsewhere) and thus to a slowing of population growth in recent decades.
But equally one can point out that without our technology, it simply wouldn't be possible to support over 6 billion people, and we would devastate the environment if we were to try doing so. So where does this leave us on whether technology increases or reduces our impact on the environment?
My view is this. Technology can do both. We employ technology because it makes things easier to do. It can do this in various ways:
- It can substitute for human labour. For example, a man who spends 30 mins walking to work each day might buy a car to reduce the journey time to 10 mins. Getting to work is now easier and more comfortable, but his environmental impact has increased and he will be using more resources. E.g. instead of moving one human to and from work, he's now moving one human plus a ton or two of metal and thus using more energy.
- It can enable us to do things we couldn't or wouldn't do before. E.g. the man who buys a car to shorten his journey to work now visits his relatives 60 miles away several times a year, where previously he would have used public transport and only gone once or twice at most. Again this increases the impact on the environment, but this time it is because the man is engaging in more activities than he used to. Another example is the summer holiday abroad that many people take which they could not do were it not for the advent of air travel.
- It can enable us to do things with fewer resources. Suppose the man who bought the car above, later on buys a new car with twice the fuel efficiency. His journeys to/from work and his relatives now have a lower environmental impact since less fuel is needed to power these journeys.
- It can enable us to tap new or previously unconsidered resources. For example, the internal combustion engine indicated that some black gooey liquid, commonly called oil, actually has its uses and advances in pumping and drilling technology enabled us to extract oil from previously inaccessible places. This of course had a considerable environmental impact, though supporting 6 billion people without such a concentrated portable energy source would likely have devastated the environment were it to be tried.