Useless Arithmetic:

Why Environmental Scientists Can’t Predict the Future

In Review

by Orrin H. Pilkey and Linda Pilkey-Jarvis. 256 pages, cloth, $29.50. Columbia University Press, New York, 2007.

cover thumbnail, book showing a fish skeleton superimposed over many numbers

What do the collapse of fisheries, beach loss, invasions by destructive exotic species, and sea level rise have in common with nuclear waste disposal and open-pit mine toxic leakage? As Orrin Pilkey and Linda Pilkey Jarvis point out in Useless Arithmetic, each of the above environmental issues provides an example of the failure of one of the most important items in the environmental scientist’s toolbox: the mathematical model.

Do your eyes glaze over at the mention of mathematical models? You’re not alone. In fact, once the modelers get involved in an environmental issue, grassroots citizen involvement gets shoved aside. When the models get brought in, those of us without an extensive grounding in math above the basic algebra level might feel a bit out of our depth.

And that would be just fine (if a bit intimidating) if the mathematical models accurately described the world. But those models don’t often describe the real world with any accuracy. In fact, mathematical models are often so divorced from the real world they are intended to describe, and the figures on which the models are based often chosen so arbitrarily, that basing decisions on those models can actually hasten the rate of damage done to the environment. At a minimum, modelers often incorporate “fudge factors” into their models to achieve the results they were looking for in the first place.

Take Yucca Mountain, the US’s proposed permanent high-level nuclear waste storage facility in the Mojave desert in Nevada. Faced with the prospect of assuring the public that the dump would remain leak-proof for 10,000 years – later expanded by court decree to a million years – environmental scientists, geologists, hydrologists, and engineers took it upon themselves to render mathematically the entire mountain, its structure and surroundings, the flow of water around and through it, and a host of other climatic, biotic, and geologic factors. This was done to determine whether highly radioactive waste placed in storage within the mountain would stay there for the requisite number of millennia. Imagine writing the math to cover every layer of rock in the mountain, unseen except through sampling and remote sensing, and trying to account for every hairline crack, then using that data to predict how the mountain will change – down to that same hairline crack level – after 10,000 years of earthquakes in the seismically active Mojave.

The Yucca Mountain modelers’ chief concern wasn’t the cracks in the mountain, though, so much as the water that would leach the wastes through those cracks. The local water table is 2,000 feet below the surface, and the mountain is in a basin with no outlet to the sea. But 12,000 years ago, there were gigantic freshwater lakes in the Mojave. And not too long before that, water flowed from what we now call Death Valley, a similar basin only a few miles west of Yucca Mountain, into the Pacific Ocean. What will the climate be like in the Mojave in another 10,000 years? Any claim that one can model local conditions that far in advance is just ludicrous.

Pilkey and Pilkey-Jarvis are no Luddites: They concede that modeling has its place, as long as each model’s assumptions, and limitations, are stated up front. Their readily accessible book should be read by any activist who’s ever had to face off against the opposition’s engineers.

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