Numbers behind the folly

Following the last post: I have found an interesting report on ecological devastation of our planet published by WWF and Zoological Society of London. The report claims that we now have the ecoligical impact equivalent to 1.3 times the capacity of planet Earth, that is we are overusing our environment by 30%. This sounds - and if true it is - really scary.

But my post deals with a small set of numbers at the core of the report. While the ecological impact per person in high income countries is 2.9 times greater than for the middle income countries the population of the middle income countries is 3.2 times greater. This more than compensates the relative overall impact. Moreover, there are two additional effects at play: first, the inevitable and laudable wish of the people in the middle income and low income countries to improve their living standards. Second the concentration of the population growth in these regions. As a result, simple math would show that future growth of the overall impact would be the fastest exactly there, coming from the combination of these two factors. The industrialised, high income nations would play smaller and smaller role in the global consumption.

The authors do focus mostly on the `per person' indicators, but even they do recognize the overall impact of the population growth:

There are many different strategies that
could reduce the gap between human demand
on nature and the availability of ecological
capacity. Each of these strategies can be
represented as a sustainability wedge that
shifts the business-as-usual path towards one
in which, when these wedges are combined,
overshoot is eliminated
One way of organizing wedges is to link
them to the three factors that determine
footprint. Some strategies in the per person
consumption and technology wedges, such
as insulating buildings, produce quick results
for shrinking overshoot. Other strategies,
such as those that would reduce and
eventually reverse population growth, may
have less impact in the short term, but lead
to large cumulative declines in overshoot in
the longer term.

Sounds easy. But can anyone tell any reasonable way of invoking such a strategy for reversing the population growth?