Discussion
Most of those pleading for Zero Growth are doing so out of a concern for the environment - and perhaps in particular concerns about the sort of environment this generation should leave to coming generations. But then, what is it that should not grow?
The basic cause of the environmental problems is that consumption has grown very strongly during this century - in particular during the latter half of it. Consumption is always dependent on a flow of natural resources and this is resulting in an impact on the environment, in use of natural resources and in emissions and wastes. This is expressed by the Paul Ehrlich formula
I = P * A * T
where I is the Impact on the environment resulting from consumption, P is the number of Population, A stands for Affluence, or consumption per capita, and T for the impact on the environment per unit of consumption. The T has been chosen for this latter factor because the impact on the environment per unit of consumption depends on the Technology used to satisfy human consumption. Better technology, from an environmental point of view, more eco-efficient technology, reduces the impact on the environment per unit of consumption. Improving eco-efficiency or resource productivity reduces the factor T.
Looking now at this formula from a global perspective it is evident, that P will grow. World population has just passed 6 billions. It is now growing with about 80 millions per year and projections show, that another 3 billions will probably be added during the next 5 decades, and most likely 2 billions more during the latter half of the 21st century, with world population perhaps stabilising around 11 billion.
Of course this projection could turn out to be on the high side and any effort to stabilise world population at a level lower than 11 billions will be well worth. But to plead for Zero Population Growth is quite unrealistic. To equate Zero Growth with Zero Population Growth does not make sense.
What about the A-factor then, should no growth of this factor be the aim of Zero Growth. Also this is quite unrealistic seen in a global perspective. The reason simply is, that even if it would be possible to stop growth in the per capita consumption in the rich industrialised countries of the world average global consumption per capita will inevitably grow, because the populations of the developing countries certainly will strive to improve their living conditions. And without improved living conditions in these countries the ongoing population growth, which predominantly takes place in these countries, may not be brought to an end.
On my website there is a Global Consumption Growth Calculator which can be used to demonstrate, that growth in average consumption per capita is inevitable on a global scale - unless unrealistic assumptions on dramatic reductions in the consumption in the industrialised countries are made. No Zero Growth here either.
There remains then the T-factor, the possibility of increasing eco-efficiency or resource productivity by improved technology. As a matter of fact the Growth Calculator mentioned above also shows, how much resource productivity should be increased in order to avoid, that the growing global consumption will result in an increased impact on the environment. With the likely growth of global consumption by a factor 5 over the next 5 decades resource productivity should be improved by about 3% p.a. to achieve this.
To me Zero Growth means that the impact on the environment resulting from consumption, the I in the Paul Ehrlich formula, that this I should not grow. Reducing population growth and the growth in the consumption in the industrialised countries would help to achieve this goal. But it can not be achieved without reducing the T-factor, by increasing resource productivity radically over the next decades - to do more with less, as Buckminster Fuller said.