Are multiple concurrent factors the norm for any system?
Or are there systems out there that mainly respond to just one factor at a time?
As many of you who have been reading this newsletter will know, I am quite interested in what happens when multiple factors act upon a systems simultaneously. In my case, the system is typically soil, and the multiple factors are drawn from a pool of global change factors. It seems quite clear that global change is inherently a multi-factorial phenomenon, with many factors active at the same time in any given location.
Sometimes when thinking about a problem it is useful to try to turn the question on its head. So: are there instances where ideally only one, or maybe just very few factors act on a given system, outside of the lab and experiments, like in reality? I am having a hard time coming up with any examples from ecology. Maybe there are other fields in the natural sciences (or beyond) where this is the case? Or maybe this is just because I am insufficiently knowledgeable about such areas, and if I speak with anybody who is an expert in a field, it will become clear that this is the same everywhere: all systems respond to multiple inputs all the time?
Take a nerve cell, I am sure it receives multiple inputs, or any cell anywhere for that matter. Or a muscle, any organ and any organism. But how about a chemical reaction? Or how about a physical system, or an engineered system? Take for example a park bench, that’s pretty simply thing, will only one factor at a time ‘work’ on this object? I am not so sure, perhaps it slightly warms up expands because the sun is shining on it, and it’s slightly wet from a recent shower, perhaps some of the paint has chipped off some from someone’s backpack scraping it, and now some fungus is starting to grow in the wood. Seems like quite a few factors could act on this object. But are they all relevant? And relevant for what? Is it relevant to understand the stability of bridge?
Is it sufficient to make this point about multiple influences if you have a long list of potential factors that could affect an object or process? I think it would be easy to come up with this list for anything. But is this sufficient to make the case? I don’t think so, because they may not act all at the same time.
Do you know any system that mainly deals with one type of ‘input’ at a time only, outside of an experiment in the lab? Of course in the lab, there are plenty of examples, because this is how we do our experiments. If you know of examples, I’d be very interested in hearing about it.
I really enjoyed reading your thoughts, and they inspired me to reflect more deeply on the multi-factorial nature of ecosystem responses. I agree with your perspective, though I’d like to share a slightly different viewpoint.
While it's true that any system or object is influenced by multiple factors, I wonder if the dominant drivers of system change are not necessarily the combined effects of many factors, but rather a few key ones. For example, in the case of neurons that you mentioned, the primary factors affecting them might be electrical currents and neurotransmitters. For a bench exposed to the elements, the key drivers could be sunlight, moisture, and temperature (It depends, as if it's raining, then both moisture and temperature are present; on a sunny day, there may be no moisture). Other factors may still exert influence, but their effects are relatively minor. For instance, body temperature or alcohol can impact neural activity, but under normal circumstances, their effects are limited.
In current global change multi-factor experiments, we often focus on the number of factors involved, but not on the strength or dominance of individual ones. I understand that incorporating this consideration may significantly increase experimental complexity, but perhaps it would better reflect real-world conditions.
I really enjoyed this thoughtful exploration of how multiple factors interact in systems. It seems like, as you said, most systems are constantly shaped by multiple inputs.
And in a larger sense, this points to how interconnected everything is. We are all part of these complex systems where many factors continuously influence one another.