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Food for thought May 8, 2011

Posted by Ezra Resnick in Science.

In The Omnivore’s Dilemma, Michael Pollan gives a thought-provoking account of where our food comes from, exploring the effects of modern food industry on our health, our environment, and our culture. The picture is not pretty, and it involves many thorny political and ethical issues, but Pollan provides well-reasoned arguments grounded in science, and his analyses seem fair and balanced.

I was a bit dismayed, however, by how the scientific method is represented in the chapter on organic farming. In that chapter, Pollan presents the views of English agronomist Sir Albert Howard, who provided much of the philosophical foundations for organic agriculture. Howard identified the 19th-century German chemist Baron Justus von Liebig (you can tell from his name that he’s evil) as the root of the problem. It was Liebig who

set agriculture on its industrial path when he broke down the quasi-mystical concept of fertility in soil into a straightforward inventory of the chemical elements plants require for growth. At a stroke, soil biology gave way to soil chemistry, and specifically to the three chemical nutrients Liebig highlighted as crucial to plant growth: nitrogen, phosphorus, and potassium, or to use these elements’ initials from the periodic table, N-P-K… Much of Howard’s work is an attempt to demolish what he called the “NPK mentality.”

… In Howard’s thinking, the NPK mentality serves as a shorthand for both the powers and limitations of reductionist science. For as followers of Liebig discovered, NPK “works”: If you give plants these three elements, they will grow. From this success it was a short step to drawing the conclusion that the entire mystery of soil fertility had been solved. It fostered the wholesale reimagining of soil (and with it agriculture) from a living system to a kind of machine: Apply inputs of NPK at this end and you will get yields of wheat or corn on the other end. Since treating the soil as a machine seemed to work well enough, at least in the short term, there no longer seemed any need to worry about such quaint things as earthworms and humus [the organic matter in soil].

It turns out, however, that growing vast monocultures of synthetically fertilized crops produces plants that are less nourishing, and more vulnerable to diseases and insect pests (necessitating chemical insecticides), among other problems. Today’s food system pollutes the environment and is completely dependent on fossil fuel energy, making it unsustainable. This is certainly a bad state of affairs, and while Pollan suggests that modern “industrial organic” farming is not a very good alternative either, he goes on to present a fascinating profile of a “management-intensive rotational grazing” farm which utilizes the natural symbiosis of various plants and animals to create produce in a manner that is both sustainable and much healthier for all involved. In his discussion of the “limitations of reductionist science,” however, I think Pollan slightly misses his mark:

To reduce such a vast biological complexity to NPK represented the scientific method at its reductionist worst. Complex qualities are reduced to simple quantities; biology gives way to chemistry. As Howard was not the first to point out, that method can only deal with one or two variables at a time. The problem is that once science has reduced a complex phenomenon to a couple of variables, however important they may be, the natural tendency is to overlook everything else, to assume that what you can measure is all there is, or at least all that really matters. When we mistake what we can know for all there is to know, a healthy appreciation of one’s ignorance in the face of a mystery like soil fertility gives way to the hubris that we can treat nature as a machine.

The “NPK mentality” is contrasted with Howard’s holistic approach:

The notion of imitating whole natural systems stands in stark opposition to reductionist science, which works by breaking such systems down into their component parts in order to understand how they work and then manipulating them — one variable at a time. In this sense, Howard’s concept of organic agriculture is premodern, arguably even antiscientific: He’s telling us we don’t need to understand how humus works or what compost does in order to make good use of it. Our ignorance of the teeming wilderness that is soil (even the act of regarding it as a wilderness) is no impediment to nurturing it. To the contrary, a healthy sense of all we don’t know — even a sense of mystery — keeps us from reaching for oversimplifications and technological silver bullets.

Having an informed sense of all we don’t know is indeed crucial — and it is a defining characteristic of a good scientist. But that is not the same as embracing mystery and ignorance. To improve our lives we need to understand the world better, and that often involves figuring out the mechanisms at work behind complex phenomena. The charge of “reductionism” is nothing but an empty slogan: “reductionism” is an ill-defined term, mainly used to denigrate the scientific method by those who don’t understand it or who desperately don’t want science to provide a materialistic explanation of their most cherished mysteries. In Darwin’s Dangerous Idea, Daniel Dennett distinguishes between reductionism (which is generally a good thing) and greedy reductionism (which is not):

There is no reason to be compromising about what I call good reductionism. It is simply the commitment to non-question-begging science without any cheating by embracing mysteries or miracles at the outset… But in their eagerness for a bargain, in their zeal to explain too much too fast, scientists and philosophers often underestimate the complexities, trying to skip whole layers or levels of theory in their rush to fasten everything securely and neatly to the foundation. That is the sin of greedy reductionism, but notice that it is only when overzealousness leads to falsification of the phenomena that we should condemn it… It is not wrong to yearn for simple theories, or to yearn for phenomena that no simple (or complex!) theory could ever explain; what is wrong is zealous misrepresentation, in either direction.

There is no virtue in preserving mysteries, and natural phenomena don’t become any less wonderful or beautiful when you understand them better. The fact that some scientists have made mistakes by presuming to know more than the evidence supports does not reveal any inherent limitation of the scientific method — which is merely our best honest effort to gain reliable knowledge of the world. There is no reason why the “mysteries” of soil fertility cannot in principle be completely understood by science. Of course, we must constantly be wary of oversimplification, and maintain a healthy appreciation of our areas of ignorance. But announcing in advance that certain mysteries will never be solved by science is equally arrogant. We must not mistake what we currently know for all there is to know, but as for what we can know — who knows?


1. Ezra Resnick - May 13, 2011

As Darwin wrote in the introduction to The Descent of Man:

Ignorance more frequently begets confidence than does knowledge: it is those who know little, and not those who know much, who so positively assert that this or that problem will never be solved by science.

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