The Demographics of Your Ecological Footprint

Ecological footprints are an important set of algorithms by which we are able to put a number on our environmental impact. Our use of resources (and the resulting pollution of the environment from the use of those resources) obviously rises with income. The more of us there are who are economically well off the worse it is for the environment. The Economist reports on a paper published recently in Demography, the prestigious journal of the Population Association of America, dealing with a new twist on this issue. Emilio Zagheni of the Max Planck Institute in Rostock, Germany, has shown that carbon footprints (a key indicator of resource use) rise steadily by age from the teen years until peaking in the mid-60s and then declining a bit after that. This demonstrates that it is not simply a matter of how many people there are, if we want to know the environmental impact--the age structure also matters.

Carbon emissions ebb as people enter old age. Because most rich countries are ageing, demography should therefore reduce atmospheric pollution. And it will—eventually. But the reduction does not begin until people are in their mid-60s and for the next decade or so, the number of people in the most polluting age group (60 to 64) will rise even more than the number of less-polluting geriatrics. In America in 2020 there will be 2.4m more people aged 75-79 than at present; but there will be 4.4m more 60- to 64-year-olds.
The growth of heavily polluting age groups will be still more marked in younger countries which are beginning to reap the economic benefits that come from an increase in the relative size of the working-age population. Members of this cohort will produce more pollution until they retire, meaning that the climate-change benefits of ageing populations will not kick in until 2050 at the earliest.