Sunday, January 4, 2009


Holdren, Intolerance of Science, and I=PAT

The new presidential science advisor appears to dislike economists and to desire scientists to keep quiet about any scientific theory that sheds doubt on environmentalist polices. First, from Dr. Holdren's own writing, The Meaning of Sustainability: Biogeophysical Aspects by John P. Holdren, Gretchen C. Daily, and Paul R. Ehrlich:

Confusion about the sensitivity of those conditions and processes to disruption is evident in the comment attributed to economist William Nordhaus that only 3 percent of gross national product (GNP) in the United States depends on the environment. In fact, the entire GNP in the US. depends, ultimately, on maintaining the biophysical requisites of sustainability. Furthermore, the importance of agriculture (the economic sector to which Nordhaus apparently was referring) is vastly underestimated by its present share of GNP.

The greatest disparities in interpretation of the relationships between the human enterprise and Earth's life support systems seem, in fact, to be those between ecologists and economists. Members of both groups tend to be highly self-selected and to differ in fundamental worldviews. Most ecologists have a passion for the natural world, where the existence of limits to growth and the consequences of exceeding those limits are apparent. Ecologists recognize that a unique combination of highly developed manual dexterity, language, and intelligence has allowed humanity to increase vastly the capacity of the planet to support Homo sapiens (Diamond 1991); nonetheless, they perceive humans as being ultimately subject to the same sorts of biophysical constraints that apply to other organisms.

Economists, in contrast, tend to receive little or no training in the physical and natural sciences (Colander and Klamer 1987). Few explore the natural world on their own, and few appreciate the extreme sensitivity of organisms -- including those upon which humanity depends for food, materials, pharmaceuticals, and free ecosystem services -- to seemingly small changes in environmental conditions. Most treat economic systems as though they were completely disconnected from the planet's basic life support systems. The narrow education and inclinations of economists in these respects are thus a major source of disagreements about sustainability.

Second, from The IPAT Equation and Its Variants Changing Views of Technology and Environmental Impact Marian R. Chertow, Journal of Industrial Ecology, 2001:

IPAT is an identity simply stating that environmental impact (I) is the product of population (P), affluence (A), and technology (T).


This looked crazy to me when I first saw it, so I should explain that the equation does make sense if its terms (in particular, impact and technology) are defined clearly. For example, the identity might set

Impact = Tons of sulfur dioxide

Technology = Tons of sulfur dioxide per dollar of income

Tons of sulfur dioxide = population * (income/population)*(Tons of sulfur dioxide per dollar of income)

Now let's go on.

... for Commoner, environmental impact is simply the amount of pollutant released rather than broader measures of impact; for example, the amount of damage such pollution created or the amount of resource depletion the pollution caused.4 His task, then, is to estimate the contribution of each of the three terms to total environmental impact.

Much to the consternation of Ehrlich and Holdren, Commoner’s effort to measure impact as amount of pollution released leads to the conclusion that technology is the culprit in almost every specific case he examines. Commoner goes on to compare the relative contributions of the three IPAT variables arithmetically: Population, affluence (Economic good/Population), and technology (Pollutant/Economic good), in examples such as detergent phosphate, fertilizer nitrogen, synthetic pesticides, tetraethyl lead, nitrogen oxides, and beer bottles. He concludes that the contribution of population and affluence to present-day pollution levels is much smaller than that of the technology of production. He calls for a new period of technology transformation to undo the trends since 1946...

Dr. Holdren's response was energetic.

Following the publication of The Closing Circle (Commoner et al. 1971a), full-scale academic war erupted between Ehrlich and Holdren on the one hand and Commoner on the other.... Their evident fear comes from “the possibility that uncritical acceptance of Commoner’s assertions will lead to public complacency concerning both population and affluence in the United States” (1972b, 16)....

At this stage Commoner brought to light a letter Ehrlich and Holdren sent to colleagues in which they reveal that they had urged Commoner not to engage in debate about which of the factors was most important because it would be counterproductive to achieving environmental goals. Commoner takes great umbrage at the idea of avoiding public discussion of scientific findings in favor of private agreements that, in turn, erode democracy and “the survival of a civilized society” (1972b, 56). Commoner identifies what he believes to be behind the debate: that “Ehrlich is so intent upon population control as to be unwilling to tolerate open discussion of data that might weaken the argument for it” (1972b, 55).

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