Measuring human impact on the planet
Many people worry that unchecked population growth will eventually cause an environmental catastrophe. This is an understandable fear, and a quick look at the circumstantial evidence certainly shows that as our population has increased, the health of our environment has decreased.
However, the issue is bigger and more complex than just counting bodies.
In reality, there are many factors at play. Essentially, it is what is happening within those populations—their distribution (density, migration patterns and urbanisation), composition (age, sex and income levels) and, most importantly, their consumption patterns—that are of equal, if not more, importance than just numbers.
The 'IPAT equation', first devised in the 1970s, is a way of determining environmental degradation based on a multiple of factors. At its simplest, it describes how human impact (I) on the environment is a result of multiplicative contributions of population (P), affluence (A) and technology (T).
Environmental impact (I) can be considered in terms of resource depletion and waste accumulation; population (P) refers to the size of the human population; affluence refers to the levels of consumption by that population; and technology (T) to the processes used to obtain resources and transform them into useful goods and then wastes.
As well as bringing the link between population and environment to a wider audience, the IPAT equation encouraged people to see that environmental problems are caused by multiple factors that, when combined, produce a compounding effect. More significantly, it showed that the assumption of a simple multiplicative relationship among the main factors generally does not hold—doubling the population, for example, does not necessarily lead to a doubling of environmental impact. The reverse is also true—a reduction of the technology factor by 50 per cent would not necessarily lead to a reduction in environmental impact by the same margin.
The IPAT equation is not perfect, but it does help to demonstrate that population is not the only factor relating to environmental damage.