Why are some ecological ideas controversial?

Why are some ideas in ecology much more controversial than others? You might be tempted to say that “Ideas which apparently conflict with other ideas, or with empirical data, will be controversial.” But I think that’s wrong—in ecology there seems to be very little correlation between the amount of criticism or controversy surrounding an idea, and the theoretical and empirical support for that idea.

Just off the top of my head, here’s a list of some ecological ideas that were, at least for a time (perhaps a long time), very controversial, but for reasons largely or entirely unrelated to the available evidence:

  • Interspecific competition. Debate over the importance of competition, and how to test for it (the “null model wars”), was famously intense in the late ’70s and early ’80s. This despite the fact that there are good theoretical reasons to expect competition (see any introductory ecology textbook), and the fact that, when you do a removal experiment to look for interspecific competition, you usually find it (Schoener 1983, Gurevitch et al. 1992).
  • Density dependence. Intense as it was, the debate in community ecology over interspecific competition was nothing compared to the debate in population ecology over density dependence. But here again, you would have a hard time arguing that the debate was driven primarily by data, or even by conventional theoretical considerations—it was ultimately a reflection of very deep-seated conceptual commitments (Cooper 2007).
  • Trophic cascades. As a grad student in the mid-’90s, I lived through the “top-down vs. bottom-up wars”, as they were sometimes called, although the issues actually went beyond the question of whether communities are “mostly” structured by top-down or bottom-up forces (see the special feature in the June 1992 issue of Ecology). Even just 20 or so years later, it’s hard to understand why there was so much fuss. The most basic question—Are top-down and bottom-up effects common?—has a clear-cut answer. When we look for trophic cascades, in both aquatic and terrestrial systems, we mostly find them: removing predators causes their prey to increase, which causes the prey of those prey to decrease (Shurin et al. 2002). When we look for bottom-up effects, we mostly find them too. As for pretty much every other question, such as those about the determinants of the strength of top-down and bottom-up effects, either all the proposed answers are either unimportant or wrong, or else the available data are totally inadequate to test them (Borer et al. 2005). So rather than having silly arguments about particular cases (see, e.g., the amusingly contrasting views of Pace et al. 1999 and Chase 2000 on the implications of Spiller and Schoener 1994), we ought to be either coming up with better answers, or better data. NutNet is leading the way on the latter.
  • Neutral theory. Evolutionary biologists enjoyed the neutralist-selectionist debate so much that community ecologists decided to refight the debate themselves. And just for fun, they decided to fight it using a particular kind of data (relative abundance distributions) which evolutionary biologists had already found to be inadequate to the task of distinguishing neutrality from non-neutrality.*

Contrast the above—intense controversies that arose and often persisted in the absence of much data, or even despite a pretty clear-cut empirical consensus—with the history of the intermediate disturbance hypothesis, which has never been a very controversial idea despite a horrible empirical track record (much worse than that of trophic cascades, density dependence, interspecific competition, or neutral theory), and being based on outright logical fallacies. Or think of keystone predation, the prevalence of which has been the subject of active research and ordinary scientific discussion, but never vociferous debate, even though the empirical evidence could hardly be considered to be more clear-cut than that for, say, trophic cascades.

The same question about the origin of controversies could be asked in other fields as well.** I’m no expert, but as far as I know sexual selection and sexual conflict was a pretty well-developed body of evolutionary theory, well-integrated with a fair bit of data (Arnqvist and Rowe 2005). Not a topic that would seem ripe for a big controversy about fundamentals—until Joan Roughgarden created one pretty much single-handedly.

And that’s probably part of the answer. If someone really prominent says something controversial, lots of people often pay attention. In ecology, Don Strong had a prominent role in the controversies over both interspecific competition and trophic cascades, and Steve Hubbell pretty much single-handedly kicked off the neutral theory debate. In evolution, Gould and Lewontin single-handedly created controversy over the “adaptationist programme”. But personal fame isn’t sufficient. In evolution, I don’t think many people paid much attention to Lynn Margulis’ stranger claims about “symbiogenesis” as an alternative to natural selection. And in ecology, Hal Caswell proposed a version of neutral theory in 1976 but as far as I know failed to kick off anything like the recent controversy over Hubbell’s neutral theory.

So, when this blog makes me massively famous and influential, what controversy would you like me to create? Because with great power comes great responsibility. 😉

*I actually think it’s very valuable that ecologists now collectively have a much better sense of what sort of dynamics distinguish neutrality from non-neutrality. I just think we learned it the hard way.

**And in fact it has. But I haven’t read the enormous social science literature on this. You get the background research you pay for on this blog.

20 thoughts on “Why are some ecological ideas controversial?

  1. Happy New Year, Jeremy!

    I can think of plenty of existing ones… but I’ll limit myself to just a couple, which you’re free to develop.

    (1) Empirical vs theoretical ecologists: All your models are wrong vs all your data are belong to us crap. A microcosmologist’s take might also incorporate the “model experimental systems are crap compared to natural systems” vs “the natural world is too bloody messy to study rigourously” that’s been discussed elsewhere already.

    (2) Single vs multi-trophic level community/foodweb models. You’ve touched on this above (interspecific competition), and it’s a personal bugbear of mine, with some reviewers dismissing some of my papers because the models don’t include predation. “But all models are wrong!” I want to shout. “And you forgot to include all the other important interactions in your (stupid) wrong model (mutualisms, parasitism, intra-guild predation, …)”. I think it’s far more important to see what we can learn from the different approaches than simply dismissing those that don’t include our favourite interactions.

    But I suppose these are existing controversies. Why don’t you create a controversy that’s sexy right now. The irrelevance of ecological dynamics for evolution and vice-versa.

  2. Just klicking on some of your links showed me that Joan Roughgarden published her kick-off paper in Science, whereas Hal Caswell published his non-controversy-starter in Ecological Monographs. Maybe a second requirement to start a controversy is to publish in … you know which ones.

    • Nah. Hubbell’s neutral theory was first published in Coral Reefs after Nature rejected it. Only when his book came out did the controversy begin. And IIRC, the battles over intersp. comp. and density dependence did not really involve Nature or Science papers.

  3. There are NO controversial ideas in ecology, and there never have been. You are just creating a controversy by bringing it up. 😉

    Seriously though, I think you pretty much answered your own question, i.e. some combination of a lack of quality data to address the topic at hand, which leads to various forms of complex hand waving, combined with the principal one way that the human ego manifests its need for attention in the academic environment. Pretty straightforward I think.

    • “There are NO controversial ideas in ecology, and there never have been. You are just creating a controversy by bringing it up.”

  4. Jeremy, thanks for another good post.

    I think a common ingredient in ecological controversies is an attempt to make inferences about important processes from easily collected survey data. All of your examples (except maybe trophic cascades) have this in common. It’s hard to resist the temptation: Go out and collect some observational data and then conduct an ingenious analysis to answer a fundamental process question. It fuels controversy because the claims can’t be supported (typically many other processes can produce the same pattern) and, because the data are easy to come by, the debate attracts lots of participants. I think the moral of the story is that if we want to learn about processes, we need to study them directly instead of giving in to the temptation of pattern interpretation.

  5. belated comment by an amateur reader — I’d bid for coming up with a highly complicated model of the deep biosphere in which elaborate specialized structures are built in the pores of the rock by bacterial communities, slowly, over vast time, accomplishing great things as cooperators. Take off from straightforward observations like http://dx.doi.org/10.1016/0964-8305(92)90058-V

    and elaborate from there to assert finding evidence by looking at the structures that bacteria are busily trying to form on the inside of oil pipelines after being ripped out of their environment and call those evidence of self-assembling complexity then extrapolate back to what they could have been doing way down where they came from.

    Maybe it’s more of a science fiction novel than an ecological controversy; perhaps both?

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  9. Do you have any entries on the neutral theory debate (other than the “null” and “neutral” models entry)? Alternatively, can you recommend a good recent survey? I want to learn more, but s always remain hindered by my lack of fundamentals.

    Also, would the group-selection vs. inclusive-fitness debate be a real controversy? Or is it just Wilson stirring up trouble? I was under the impression that this debate keeps re-emerging over the years, so it can’t be fully attributed to Wilson.

    • The controversy over inclusive fitness isn’t just one famous person stirring up trouble. But you could argue that it’s a few famous people.

      Re: neutral theory, I’d recommend starting with an evolution textbook or review. Population geneticists have always been crystal-clear on what “neutral” means, and how “neutral” and “drift” don’t mean the same thing. Ecologists treat both terms in a much more loosely-defined way, which leads to a lot of confusion in the literature. Not that you shouldn’t read the ecological literature on this–but I think it’s best to start from a firm foundation in the evolutionary literature.

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