The Benefits of a Reductionist Approach

I have been called a reductionist quite a few times. I never know how to respond. Am I a reductionist? If so, is that a bad thing? Why is there resistance to the approach? So I did some investigation. What I found is the whole topic is like one of those rotating mix and match puzzles for kids (Figure 1). On the top are the multiple definitions of reductionist approaches. On the bottom are the multiple holistic and complexity/emergence definitions, the alternative to the reductionist approach. In the middle is the context of these comparisons, whether from philosophy, science, biology, physics, ecology, or agroecology¹. Each combination brings up different issues, questions, and answers.

I will not address all the puzzle combinations because I don’t think they matter in the context of agriculture and agronomy. Rather, I will focus my discussion of this issue on two questions. First, does the reductionist approach apply to the systems agronomists work on? And second, does the reductionist approach produce useful tools for farm management? I will answer these questions with regard to agroecology, since it is where the issue of holism and emergence arises in agriculture.

A Reductionist Approach

There are many views of what a reductionist approach is and its faults. In fact, many of the criticisms of reductionism are misplaced, having nothing to do with actual reductionism (or the closely aligned and similarly maligned mechanistic approach and linear thinking). You can read about those in the footnotes². Here, I will stick with this: a reductionist believes big things are reducible to small things and their interactions. The combination of and interaction between small things produce the big things through physico-chemical³ mechanisms, even if we can’t identify or understand them for various reasons. Nearly everyone agrees that this approach has been tremendously successful in solving problems, even those who believe that more holistic/emergent approaches are needed (Heng, 2013; Segerstråle, 1992). And it is a crucial part of the scientific method (Aiken, 2012).

Consider a car. It is a complex system. To get the desired results of transportation, the fuel injection system must mesh with the driveshaft system, which must mesh with the steering and wheel system and all the other critical systems in very specific ways. It is a complex system of interacting systems.

To engineer, build, or repair a car system requires a reductionist view, with the understanding of each part or sub-system, and how they are designed to work together, or at least an instruction manual written by those who understand the system of systems.

This brings me to my first point: we are all reductionists most of the time. So calling someone a reductionist is both obvious and amounts to “you are more of a reductionist than I am.”⁴

Reductionism as Oversimplification?

One criticism of the reductionist approach is worth a deeper look. When facing complexity beyond our current ability to understand, the reductionist approach seeks to simplify it by narrowing in on the relevant factors. This can go too far, which results in critiques of reductionism for not incorporating all the relevant factors (Wimsatt 2006; and perhaps applies to my trying to tackle this issue in a blog post🙂). The issue is often of where to draw the boundaries on the system being examined. Oversimplification of ecological systems is a reductionist temptation and can lead to problems. However, rather than being linked to reductionism, it is more related to the one’s definition of relevance.

There are pragmatic arguments for excluding factors from solutions that are not manageable, or making some assumptions about whether factors are important to a specific analysis. A cropped field is an open ecosystem, the boundaries are somewhere between the surface of a crop plant and everything. Social factors might not be included because they are out of the control of the farmer, or because they change based on the latest farm bill, or international markets, etc. My point remains; the problem of reductionist oversimplification does not make complexity and emergence more useful. There is nothing about the reductionist approach that limits it from being multi-disciplinary or considering all the factors. The problem is how the strategy is employed rather than the strategy itself. The solution is not to oversimplify.

A Holistic Approach and Emergence

The opposing view is that some wholes or systems are not reducible to their parts⁵. Holism considers the whole system as a unified entity with properties that emerge from the whole or come about by complexity. The emergent properties are the part that the reductionist approach cannot explain.

For emergence, water is a famous example; the parts hydrogen and oxygen differ greatly from the water formed by combining them. The emergent properties of water cannot be explained by just looking at the properties of oxygen and hydrogen. However, most of the serious arguments about holism, emergence, and reductionism are about things like consciousness, or free will, or life itself (Kim 2006; Aiken 2012; Wright 2021; Corning 2002). None of these things are easily reduced to their parts and so emergence is one explanation.

As with reductionism, there are various definitions of holism and emergence (Kim 2006), and similarly, many of those promoting holistic approaches are actually addressing other issues. There are weak and strong versions of emergence, with weak being compatible with reductionism (Hossenfelder, 2019; O’Connor 2020). There are distinctions between complex and complicated⁶.  There’s much more. It’s complicated. Or is it complex? Let’s get back to my questions.

Reductionism is Appropriate for Cars, Cornfields, and other Complex Systems

So, does the reductionist approach apply to the systems agronomists work on? In agronomy, I am not concerned with human consciousness, free will, or the source of life. I am not working in the intersection of quantum and Newtonian physics. Those don’t concern me. I am looking at a cornfield. Or even a complicated intercrop rotated with a cover crop mixture. Neither crosses the line where emergence is most often discussed, and without emergence, a holistic approach is nothing more than a reductionist approach with an expanded system boundary.

Even agroecology’s use of complexity and emergence (Vandermeer and Perfecto, 2017) does not cross this line. One example is from a prolific group of agroecologists who, over the past decades, have described an organic coffee production system in Southern Mexico (Jackson et al. 2012; Vandermeer et al. 2010, Vandermeer et al. 2008; Philpott et al. 2009). The system consists of at least 13 species of insects and fungi interacting to control four coffee pests though six ecological processes; competition, predation, parasitism, hyperparasitism, disease, and mutualism (Vandermeer et al. 2010). The systems they talk about in this context are complex, for sure, but they fall into the weak emergence, which is compatible with reductionism (See Wright 2021 and Hossenfelder 2019 for more discussion). We may not be able to understand how all these processes work together, but they are all explainable in reductionist terms.

Therefore, because agronomy does not address the topics purportedly explained by the holistic approach and emergence, reductionism is a reasonable approach to the topics, systems, and problems it does work on.

Reductionism is Useful

“Why do [holists, emergentists] find it necessary to reduce a perfectly sensible belief (that complex wholes should be explained in terms of their parts) to an idiotic travesty (that the properties of a complex whole are simply the sum of those same properties in the parts)?” … ‘In terms of,’ covers a multitude of highly sophisticated causal interactions… Reductionism, in the ‘sum of the parts’ sense is obviously daft, and is nowhere to be found in the writings of real biologists. Reductionism, in the ‘in terms of’ sense, is “the most successful research stratagem ever devised.” Dawkins, 1985.

So the reductionist approach applies to farming systems. Does it also produce useful tools for farm management? Agroecology is where holism and emergence are usually brought up in this context. So how useful has this been?

For the most part, ecology is dedicated to holism (Odum 1977) and so to complexity and emergence, although not without critique (Drury 1998). This focus continues in agroecology (Bezner Kerr et al., 2023; Katre et al. 2022; Gliessman, 2006). However, most of ecology and agroecology-I would argue the most useful part-is reductionist. Again, most of us are reductionist most of the time because it works. When, however, agroecology tries to make generalizations about complex, open systems of mixtures of mobile species, it resorts to complexity/emergence.

Back to the coffee production system example. The system they describe is indeed complex, and the research they conducted to tease out the effective agents and complex interactions is impressive, but is it more than a curiosity? The question of utility is “what from this example can be used to develop other such agroecological systems?” The papers from Vandermeer et al. do not give a straightforward answer.⁸ They say that this system developed through network structuring, nonlinearity, and stochasticity; “an ecosystem service emanating from ecological complexity.”⁷ OK. But how do we get this?

In their book Ecological Complexity and Agroecology, Vandermeer and Perfecto (2017), use hundreds of pages to detail their ideas on holism, complexity, etc. Then on the next-to-last page, they address my question. For those of us who do not intuitively understand how these systems work, as they say traditional farmers do, Vandermeer and Perfecto respond, “Our insistence on understanding ecological complexity will frequently require answering the farmer’s query, ‘what can I do?’ with the honest answer, ‘I do not know.’”

I do not know.

I can imagine the farmer continuing, “Then what good is your theory?” For all the information provided, they give no reliable method for achieving these desired emergent properties.

“Complex systems are marked by an exponential increase of information, complexity, ambiguity, emergence, and high levels of uncertainty.” “Emergence is one of the obstacles to successfully execute governance in complex systems.” Jaradat 2015.

They are not alone. “Diversify!” is the consistent call of agroecologists, and while this can result in some beneficial coincidences, a recent meta-analysis finds just diversity is not a reliable strategy (Jones et al. 2023). Why? Because the focus on diversity from the holistic/emergence viewpoint obscures real mechanisms. Reductionism works because it gives us real, understandable mechanisms to manage.

Instances of complexity and emergence in agroecology amount to a lack of reductionist knowledge of the enormous number of actions and interactions in complex systems (Figure 1) but bringing in emergence does not help.  How do you manage emergence? What do we do? Apart from its reductionist components, agroecology’s holism/complexity/emergence approach provides no answers, no specific practices, only a hope that emergence shows up, and a hope that it was not just a beneficial coincidence. Therefore, since we cannot manage for emergence, the proven, successful reductionist approach will do just fine. Why should we base our food security on chance?

“The intuitive associations this word [emergence] evokes in us do not add up to a concept robust enough to do any useful work,” Kim 2006

Reductionist Success

“One cannot achieve in other ways what reductionist science can achieve.” G.H. Walter

I’ve answered my questions. The reductionist approach 1) applies to the problems encountered in agriculture, and 2) provides management options for farmers. For these reasons and more, it is very successful. It’s not perfect, but is a proven strategy for solving simple and complex problems in agriculture.

So, am I a reductionist? Yes, very much so.

Is this a bad thing? No, not at all.

 

Update 8/4/23

• This critique of emergence came out after I wrote this. It comes from a Cornell Systems Scientist: “The idea of emergence is often summarized in the misleading trope that, “the whole is greater than its parts.” But let’s set the record straight and debunk this popular myth: the whole is always equal, never greater, than its parts.” Read the whole article here.
• Another here: “Emergence is not a theory. Emergence can only be ascribed to a phenomenon in retrospect, once you already know what has “emerged”.

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¹ Ecology’s emergence differs greatly from physicists’ emergence (Wright 2021)

² Many of the definitions of reductionism seem designed for critique rather than accuracy:

• “The whole is the sum of its parts” is a common but flawed definition. Here, “the sum of” means simple cause-and-effect relationships, while reductionism does not eliminate viewing part as having complex interactions and feedback loops.
• Reductionism results in unintended consequences (Clements and Shrestha 2004). As if messing with complex systems and unpredictable emergent properties cannot result in unintended consequences. Isn’t emergence an unintended (because you can’t) consequence of a complex system of components? Why can’t these be detrimental rather than always beneficial? This is more accurately related to the system boundary issue.
• Simply that reductionists don’t take the complex view, but rather find simpler explanations. They only address “simple cause and effect, single factor” problems. See the car example and Drury citations for an alternative view in ecology.
• Sometimes it is the degree of reductionism that is critiqued: “That is extremely reductionist.” But what is the alternative, a moderate reductionism with moderate emergence? Doesn’t make sense, unless in “extreme” they are critiquing one of the wrong definitions given here.
• A utilitarian approach, whatever works. Why this should be avoided, I do not know.
• In linking quantification to a reductionist approach (Levidow et al. 2014), agroecology has cast off from usefulness into the murky waters of complexity.
• That solutions that involve technology are reductionist, but those that involve ecology are not (Kremen et al. 2012).
• Reductionists see all the world as resources (Frank 2021). Again, not reductionist.
• Reductionism’s focus on real physico-chemical causes offends some people. This seems to be the main reason people call me a reductionist. I am so Newtonian.
• Reductionism as the explanation of something with one cause (Van Regenmortel, 2019). This too is wrong. There are many factors in crop yield, and so we never explain it by a single cause. And even when there are so many interacting factors, many unidentified, does not mean we have to resort to complexity and emergence.
• Reductionists know that working with molecules is different that working with a cell, with an organism is critically different from working with a group of organisms, and a farm is different from a watershed. As with quantum mechanics and Newtonian physics, what works at one level may not work at another level or scale; we can’t apply reductionist explanations that are true at one level of organization to the one above it (Gleiser 2022; Heng 2013). This does not refute the reductionist but rather forces them to use different strategies and explanations when the system boundary changes.

³ A term resulting from the Great Compromise of 1837 between physicists and chemists to answer the question, “What runs the physical universe?”

⁴ There are varying degrees of reductionism. Full reductionists believe that everything, in principle, can be explained in this way (Siegel 2022). Partial reductionists, like myself, draw the line somewhere this side of everything. And I am certainly not a reductionist in terms of biological determinism, the idea that human behavior is determined by our genes alone (Segerstråle, 1992). Then there are varying degrees the application of reductionism, as when someone calls an analysis “extreme reductionism”, as if one should use some reductionism along with something else (?).

⁵ There are multiple definitions of both reductionism and emergence, some contradictory. I went with the most general.

⁶ I agree with Taborsky (2014) who sees the difference between complex and complicated as mainly a matter of interpretation.

⁷ Other explanations are similar in their inability to be managed: self-organized criticality, law of universality, fourth law of thermodynamics, self-propelled, autocatalytic process, innate spontaneity (Corning, 2002).

⁸ It’s interesting that in the Vandermeer et al. coffee system, neither coffee nor two of the pest organisms involved are native to the region studied. Coffee has been grown in the region for over 100 years, but some of the pests are more recent invaders. Therefore, the system probably has nothing to do with evolutionary processes which happen, for these types of organisms, on a much longer time scale. Given that not all mixtures of natives, non-natives, insects and plants, etc. give us the desired pest control, this is probably a beneficial coincidence.

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