Agroecosystems

Agroecosystems: Complex Organisms with Nonlinear Response and Emergent Properties; A Discourse

There’s a question I’ve been pondering for years, between one field visit and another: why do we continue to think of agroecosystems as biological communities composed of individual parts? Those who work the land know this isn’t the case. Agricultural systems respond in their own way, often disproportionately to the input we give them; sometimes they don’t respond at all, other times they explode in a direction no one had foreseen.
But where does an agricultural system begin and end?
I’d like to try to provide a theoretical framework for what field experience has always suggested to me, starting with a book I found very interesting: The Ghost in the Machine by Arthur Koestler (1967).
Koestler introduces a simple and powerful concept, that of the holon. He argues that every biological entity is a whole, behaving simultaneously as a whole and as part of a whole. The agricultural system/holon is a unity, it has its own autonomy and identity, but it is always part of a larger unity of which it is a component.
A cell is a whole with respect to its components, but a part with respect to a tissue; the tissue is a whole with respect to an organ, but a part with respect to an organism. Therefore, according to Koestler, each holon has a “self-affirming” tendency, which on the one hand pushes it to preserve its own individuality, and on the other pushes it to function as part of the higher system, to pursue a specific function. Therefore, we could say that an agroecosystem is in dynamic equilibrium only when these two tendencies are balanced at all levels. The set of holons, organized on multiple levels, forms a holarchy. If we look at agroecosystems from this perspective, everything begins to take on order and form as if in a mosaic: the individual plant is a holon, but so are the rhizosphere, the phyllosphere, the individual plot, the individual farm, and the agricultural landscape of a specific area.
None of these levels, however, alone explains the behavior of the agricultural system; perhaps it is the relationship between the various levels that can explain it, the never-ending balance between autonomy and interaction. And this is where nonlinearity arises: a small imbalance at one level—for example, excessive nitrogen fertilization or the cutting of a hedge—can spread disproportionately to higher or lower levels, because holarchy does not transmit effects linearly, but amplifies or dampens them depending on how internal relationships are organized.
On this basis, some have explicitly brought the holon theory into agroecology. I am referring to the work of Bland and Bell (2007), “A Holon Approach to Agroecology,” which addresses two of the key issues inherent in classical systems thinking: the problem of boundaries and the problem of change. In ecology, we know that transition zones between one system and another are called ecotones, zones where everything is constantly moving and changing.
Can we do the same in agroecology? Where does an agricultural system end or begin? And what happens biologically at its boundaries? And yet, how do we understand that an agroecosystem never stands still, but continually adapts?
Bland and Bell (2007) propose that the farm is the clearest example of a holon, but a holon defined by intentionality. That is, there is a cohesive whole that remains so because there is a sort of imperative holding it together. This imperative is given by the farmer and the living and non-living beings that inhabit the system. The boundary, then, is not an objectively traceable line that we can draw from the outside or from the inside, but is something that is continually defined and redefined by intentions, as in ecotonal areas. The agricultural system is immersed in what the authors call an “ecology of contexts,” such as the climatic environment, the biography of those who manage it, the knowledge and traditions that inhabit and characterize it, the economic market, and even the spiritual beliefs of its inhabitants; therefore, multiple contexts that are difficult to measure and in constant evolution.
It is precisely the force that holds all this together that makes the dynamism of the agricultural system (holon) the normal condition of the agroecosystem. The agricultural system, from this perspective, is a never-ending “holding-together,” an ever-provisional result.
Bland and Bell (2007) propose a cognitive tool called flickering.
According to this tool, to understand a holon, one must shift one’s gaze, looking at the agricultural system as a whole one moment and then as a part the next, without ever focusing on just one of the two sides.
This is exactly the type of gaze needed in the field, where the same plant is simultaneously an individual, a component of a plant community, and a node in a food web.
This approach recalls the theory of epistemologist and ecologist Edward Goldsmith (1992), founder of the magazine The Ecologist, who spent a lifetime criticizing what he called the “paradigm of science”: the habit of breaking down the world into isolable parts to study them separately, losing along the way the very “strength” that holds them together.
His major work, The Way, overturns the neo-Darwinian assumption of nature as a theater of competition and random events and describes it, instead, as a cooperative order. For Goldsmith, the entire biosphere should be understood as a hierarchy of self-regulating systems, from the cell to the organism, from the ecosystem to the biosphere itself, each capable of maintaining its own homeostasis thanks to the relationships it establishes with adjacent levels: a structure very close to Koestler’s holarchy, and I would say for good reason.
One of the contributions to agroecology that I find very useful, however, is another: the distinction between homeotelic and heterotelic behavior (Goldsmith, 1992).
A biological process is homeotelic when it contributes to maintaining the order and stability of the whole of which it is a part; it is heterotelic when it perturbs or disrupts it, even though it may appear, in the short term and at a single level, perfectly efficient. This is, ultimately, Koestler’s integrative tendency interpreted from the perspective of the health of the agricultural system. Much industrial agriculture is based on heterotelic processes: it optimizes a single level, for example, the yield of a single crop in a single season; however, at the expense of the order of higher levels, such as the soil, the landscape, and geobiochemical cycles. The stability of a biological system is never a property of individual elements, but a property of relationships: of the way the system self-regulates in time and space through continuous feedback, remaining homeotelic with respect to the whole that contains it.
Think of the synapses of the brain’s neural networks. Without their action, without neurotransmitters, the network wouldn’t function.
But if we put together what we’ve said so far, we can answer the question: are soil fertility, productive stability, and the resilience of an agroecosystem emergent properties?
Before answering, it’s important to clarify what an emergent property is, because it risks becoming a catchphrase. A property is said to be emergent when it appears at the level of the whole without being present in any of its individual components, and without being deduced from the simple sum of their characteristics. It should not be confused with an additive property: the mass of a clod is the sum of the masses of its grains, and is therefore decomposable and predictable; fertility is not. The old formula applies here: the whole is not the sum, but something qualitatively different from its parts.
I believe the answer to the previous question is yes, and I also believe it’s a mistake to try to study or influence these properties by analyzing or acting on individual, isolated elements of the system.
A chemical analysis of the soil gives us the numbers of multiple elements, but it doesn’t indicate fertility, because it measures the parts, while the property exists in their intertwining.
Fertility emerges from the network of interactions, often nonlinear, between minerals, organic matter, fungi, bacteria, roots, and soil fauna: it is a property of the three-dimensional configuration of relationships, not of the components that determine it.
And there is a second trait that is very important in agroecology and difficult to translate into Italian: “retroactive feedback.” The property, once it emerges, reacts on the lower levels and constrains their behavior, just as the higher holon conditions the lower ones (cf. Koestler, 1967).
A healthy microbial community directs what individual roots can do, not the other way around. The same is true for stability: it emerges from the complexity of relationships and collapses when that complexity is impoverished beyond a certain threshold.
The idea that the form of a living system emerges from a field of relationships, and not from the sum of its components, has ancient roots in developmental biology. The concept of the morphogenetic field, theorized from the “old” embryology of Spemann and Weiss to the “epigenetic landscape” of Conrad Waddington (1942), describes precisely this: a region where the functions and form of a biological system reside not in the single element but in the whole; an area where the software that manages the system is located. Waddington called it canalization, and it is, in fact, another word for homeostasis.
Evolutionary developmental biology has revived this idea: Gilbert et al. (1996) propose the morphogenetic field as a true ontogenetic unit, mediating between genotype and phenotype, reminding us that even at the organismal level, form is a property of the field of relationships, not of context. Translating this vision to agroecology, the implications become very powerful.
Fertility, soil health, and the structure of a plant community behave like morphogenetic fields, in which what matters is not the individual component but the relationship between them, a sort of “vital glue” that maintains the system’s shape and about which we know little or nothing.
I’ll end this rant by mentioning Chaboussou. In 1985, drawing on an insight from Dufrénoy (1936), he founded the theory of trophobiosis.
With this theory, he demonstrated that a plant is not attacked by a pathogen or pest randomly, but only when soluble, unmetabolized compounds accumulate in its tissues, primarily free amino acids and simple sugars, which become available food for the attacker. This accumulation occurs when the plant loses the dynamic balance between anabolism and catabolism, an imbalance often triggered by unbalanced fertilization, excessive inputs, or abiotic stress.
This interpretation finds empirical support in the so-called plant stress hypothesis: abiotic stress conditions such as drought have been associated with increased plant susceptibility and actual pest outbreaks (Mattson & Haack, 1987). The picture, however, is far from unequivocal, and it is important to state this clearly.
The meta-analysis by Koricheva et al. (1998), however, has shown that the effect Chaboussou speaks of depends largely on the trophic guild; for example, xylophagous and sucking feeders tend to benefit, while chewing and gall-forming feeders are often penalized. This confirms, however, that here too, the configuration of relationships matters more than any single variable.
This theory, if interpreted through the eyes of Koestler, Bland, Bell, and Goldsmith, says something more profound than the agroecological rules we know: the plant itself is a holon in homeostatic equilibrium, and disease is not an invasion from the outside but the emerging symptom of the disruption of that equilibrium, an equilibrium that in turn depends on the higher level, namely the soil and the agroecosystem that hosts it.
Pathology, in this perspective, should not be fought downstream with intervention aimed at the symptom, but should be interpreted upstream as a sign of systemic malfunction.
Therefore, a complex system with nonlinear response is a collection of many heterogeneous elements, organized on multiple levels, whose behavior does not derive from individual components but from the web of their interactions. “Nonlinear” means that the effect is not proportional to the cause: the same input can produce nothing or trigger a disproportionate response, depending on the state of the system and how its internal relationships are organized. These are systems held together by continuous feedback, capable of self-regulation within certain limits but also of crossing thresholds beyond which they suddenly shift their equilibrium; systems that retain the memory of their own history and generate emergent properties that cannot be traced back to individual parts, which, once emerged, react on these individual components.
This is exactly what an agroecosystem is. And if we accept this definition, then stopping isolating the parts is no longer one methodological choice among many: it is the only perspective that respects the nature of the living system.
At this point, however, I have more questions than answers.
If the boundary of an agroecosystem is drawn by the intention with which we observe it, then every diagnosis we make depends on where we decide the system ends.
Everything becomes subjective.
So what do we do? Do we stop at the plant? The plot? The farm? The drainage basin?
Each boundary generates a different problem and, consequently, a different solution.
“Objective” phytosanitary diagnosis is always an act of interpretation. When we call a pathology a “problem,” from which level of the holon are we observing it?
Then there is a doubt worth keeping in mind, and it is exquisitely agroecological. If many energy inputs themselves act as stressors, pushing the plant toward catabolism or anabolism, then the tool we use to defend the crop could be precisely what prepares the next outbreak. The intervention designed to extinguish the symptom becomes a disruption of the holon. Are we treating it or maintaining a dependency?
Seen in this way, the spiral of inputs becomes an ecological and therefore systemic issue.
So I ask myself: is an agroecosystem that produces well only under the continuous action of external factors a healthy holon or a holon in intensive care?
Then there remains the question of time, which no technique can resolve.
Emergent properties such as fertility, resilience, and biological complexity of the soil are built slowly, season after season, while the agricultural economy rewards the short cycle.
There is therefore a gap between the time of the holon and the time of the economic market. And can we really measure the “health” of a plant or soil with a single indicator, a yield, a laboratory value? Or is health also an emergent property, discernible only in the behavior of the whole over time?
If the answer is the latter, then perhaps agroecology is the discipline of conditions: not “what I apply,” but “what relationships I make possible.”
This is a perspective that does not offer easy solutions. However, for some time now, I have suspected that this is precisely the point.
If stability and fertility are emergent properties of a holarchy in dynamic equilibrium, then plant pathology is the other side of the same coin: it is what emerges when the relational complexity of the system is impoverished, when the self-affirming tendency of a holon, such as monoculture, prevails over the integrative tendency that binds it to the larger system.
Pathology is not an enemy to be eliminated; it is a message to be interpreted.
And this is perhaps the most urgent paradigm shift for those of us who work in the field every day: to stop looking for linear causes and learn to interpret emergencies, in both senses of the word.

Francesco Di Lorenzo
Agronomist

Bibliography
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https://doi.org/10.1080/14735903.2007.9684828

Chaboussou, F. (1985). Santé des cultures: Une révolution agronomique. Flammarion. (Ed. it. Piante sane: Una nuova rivoluzione agricola).

Dufrénoy, J. (1936). Nutrition et résistance des plantes aux parasites. Annales des Épiphyties, 2, 1–34.

Gilbert, S. F., Opitz, J. M., & Raff, R. A. (1996). Resynthesizing evolutionary and developmentalbiology. Developmental Biology, 173(2), 357–372.
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Goldsmith, E. (1992). The way: An ecological world-view. Rider. (Ed. riveduta, Green Books, 1996).

Koestler, A. (1967). The ghost in the machine. Hutchinson. (Ed. it. Il fantasma nella macchina, SugarCo).

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Mattson, W. J., & Haack, R. A. (1987). The role of drought in outbreaks of plant-eating insects. BioScience, 37(2), 110–118.
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Waddington, C. H. (1942). Canalization of development and the inheritance of acquiredcharacters. Nature, 150(3811), 563–565.
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