FROM READERS.

Net Energy Cost and Population

I am responding to the Flavin/Elliott exchange of views in "Is Our Outlook For Solar Energy Too Sanguine?" (January/February).

Having read Christopher Flavin's earlier article ("Energy for a New Century"), I would like to address an idea that has received fir too little attention up to now-the idea that the Earth is now overpopulated by several-fold.

Before I am accused of switching the subject from energy to population, let me say, as Jimmy Stewart would have phrased it, "now hold on just a darned minute!" Any attempt to decouple discussions of energy from human numbers is somewhat analogous to rearranging the deck chairs on the Titanic.

Proposed solutions to the "energy problem" now facing humanity emphasize discussions of how to replace current usage levels of fossil fuels with some form of renewables, while giving little or no attention to the question of whether current usage may be already exceeding the sustainable source/sink capacity of the Earth.

In considering what number of human beings constitutes "overpopulation," the concept of mankind's permanently sustainable ecological footprint is coming into vogue as a useful analytical tool. Although the complexities that enter into the estimation of such a footprint are almost overwhelming, we have enough data at hand to allow significant order-of-magnitude estimates to be made. Ritik Dholakia and Marcus Wackernagel of Redefining Progress (www.rprogress.org) state that the footprint of the typical American lifestyle is 25 acres/capita.

Even admitting that this is a first approximation, this number should give us serious pause. Why? Because this number, when divided into the total available land area of Earth (excluding Greenland and Antarctica) yields about 600 million as the number of humans that can inhabit the planet (sustainably, in comfort, living the typical American lifestyle). This calculation devotes 50 percent of the land area to other species, a figure considered reasonable by a consensus of wildlife biologists. By the above criteria, Earth with its current 6 billion plus is now ten-fold overpopulated.

The implications for the "energy problem" are clear. First, the end of the petroleum economy is drawing near and will occur within the lifetime of today's high school and college students. Second, large uncertainties are associated with net energy calculations, given the strong bias of economists to discount the true environmental costs of...