Questioning the value of biodiversity (UPDATEDx3)

I don’t ordinarily plug individual papers in ecology journals, figuring y’all don’t need my help finding individual papers to read and deciding what you think of them. But I’m making an exception because this is important.

Writing in Trends in Ecology and Evolution, the always-thoughtful Mark Vellend reviews philosopher Donald Maier’s new book What’s So Good About Biodiversity? You should click through and read it, because the review (and by the sound of it, the book) are really sobering.

Maier reports being “stunned” that he “could not find a single argument [for the value of biodiversity] that does not have serious logical flaws, crippling qualifications, or indefensible assumptions.” And before you write Maier off as just ignorant, or as someone saying outrageous things to try to sell books, be aware that Mark thinks he’s got a point. Which doesn’t prove the book is right–but does prove it deserves to be taken seriously rather than dismissed out of hand. For instance, Mark discusses the argument for biodiversity based on the ecosystem services it provides–and notes that nobody ever talks about all the ecosystem disservices that biodiversity also provides, such as increased disease risk. And how come ecologists never argue for promoting species invasions on the grounds that it would increase biodiversity and thereby enhance ecosystem services? As Mark pointedly remarks, when it comes to valuing biodiversity, ecologists basically started with a conclusion, and then looked around for arguments to support it. It’s unsurprising that such a backwards procedure yields unconvincing arguments. It’s the same procedure that Scholastic philosophers used to find “proofs” of the existence of God, for instance, and it’s the same procedure creationists use to argue against evolution. Now in fairness, post hoc rationalizations have their place, and often they’re unavoidable. But if they’re really bad rationalizations, and if they’re not even recognized as rationalizations, then there’s a problem.

Which is something ecologists should talk more about–but we mostly don’t, at least in my experience. That’s maybe the biggest problem here. Maier concludes that not only have ecologists collectively been the victims of confirmation bias when it comes to valuing biodiversity, but they’re not talking about it. Maier concludes that there is “tacit agreement among colleagues not to rock the boat of bad reasoning – perhaps out of fear that there is no other way to defend nature and its value”. As Mark says: ouch.

Anyway, consider this another example of why ecologists should read more philosophy.

p.s. I’m a bit late to this, so for previous commentary on Maier’s book (and Vellend’s review of it), and for commentary on (and links to) a talk by Maier, see here, here, and here.

UPDATE: On Twitter, @frank_burdon asks whether Mark “lacks objectivity” because of his recent PNAS paper showing that local-scale plant biodiversity around the world isn’t changing. I’m confess I’m unclear exactly what “objectivity” means here. But if what’s meant is something like “a thoughtful, knowledgeable, self-aware person who carefully weighs evidence and arguments in order to come to conclusions he’s prepared to defend”, then Mark Vellend is one of the most objective people I know.

UPDATE #2: Just to continue the thought from the previous update, and highlight some things I just said in the comment thread. I’m well aware that Maier’s views are going to be controversial and unpopular. And I’m well aware that some people didn’t like Mark’s recent PNAS paper (though personally I’m not sure why, as I didn’t see any serious technical flaws or wild overstatements in it myself…). It’s for those reasons that I hesitated to post on this; there’s a higher than usual risk of the discussion degenerating into an unproductive shouting match. But I decided to post, as the issue is important, and interesting to me. And because in the past we’ve always been able to trust our commenters to vigorously debate controversial issues without descending into personal attacks, questioning of motives, proof by authority, etc. So let’s all make sure we live up to the high standards set by previous comment threads on controversial topics. One of the best uses of blogs is as a forum for vigorous but productive debate.

UPDATE #3: And just in the interests of being up front about my own views here: I think Maier has an excellent point about general, blanket arguments for the value of “biodiversity”. Insofar as we’re conserving biodiversity in order to achieve some instrumental goal (like maximize the level of some ecosystem service), then I think we’re much better off making narrower, case- and context-specific arguments. Arguments like “In order to ensure provision of ecosystem service X in system Y, we ought to conserve high levels of biodiversity, because alternative ways of ensuring provision of high levels of service X would be more expensive, and because doing so will not have any negative side effects.” If there are any good general, blanket arguments for conserving biodiversity always and everywhere (or preventing species invasions always and everywhere, or pursuing any particular conservation policy always and everywhere), then I suspect they’re based on intrinsic values rather than instrumental values. There’s a large philosophical literature on that, of course, but it’s not one I know well.

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34 thoughts on “Questioning the value of biodiversity (UPDATEDx3)

  1. I read the book, most of it anyway – I thought it was surprisingly entertaining, the ebook is not expensive either, so I would definitely recommend it.

    It did serve my own confirmation bias to see that a moral philosopher finds much of the ES logic wanting. Most of his inquiry doesn’t really come as a surprise, and some of it is attacking straw men, but it’s interesting to see an outsider from a field that requires strict formal logic working himself up over the published literature. A few points he raised were really interesting, I’m planning to write about that in more detail if I find the time.

    • Will be interested to see what you have to say Florian. Jeff below also seems to think he’s attacking a bit of a strawman. Which potentially gets into the tricky issue of what’s a “strawman”. Any attempt to generalize about any complex topic on which many people have opinions necessarily omits some details of some people’s opinions. Thereby leaving some scope for everyone to defend themselves by saying “Hey, that’s not (exactly) what I said! You’re attacking a strawman!” I certainly ran into this with my IDH posts. I critiqued views that are in *textbook* discussions of the IDH and yet was accused of attacking strawmen because supposedly nobody believes the ideas I’m attacking, which aren’t even part of the IDH anyway.

      I guess there has to be a balance somewhere. If there are some common threads running through many people’s opinions, I think it’s fair to identify those threads and critique them. But how common do the threads have to be for this to be a fair approach? Obviously, that’s going to be a judgement call, on which reasonable people might disagree. For instance, Doug Sheil, David Burslem, and I had a friendly, reasonable disagreement over what ideas are part of the IDH.

      Part of what’s going on here (and I’m speculating on this) may be that Maier is a philosopher, and so has a professional interest in identifying and critiquing general, exceptionless arguments. Not highly contingent, case-specific arguments of the sort I suggested in one of my updates; those aren’t philosophically interesting. So it may be that he’s going to have a tendency to read people as making general, exceptionless arguments when a non-philosopher might’ve read them differently. In which case, it’s maybe fair to complain that he’s attacking strawmen, or at least being uncharitable in his readings. But on the other hand, if a philosopher (i.e. someone who’s trained to make explicit, precise, logical arguments) has tried his best to understand what we’re saying, and yet misunderstood us, maybe that’s our fault. Maybe that’s a sign that we ecologists need to raise our collective game and do a better job spelling out precisely what we do believe and why.

      • Hi Jeremy and all,

        with regard to the comment section below, I can only recommend reading the book before discussing in too much detail what Maier allegedly said and why this is right or wrong. I liked the review by Mark Vellend and it was the reason I bought the book, but it necessarily highlights only a small part of the 500 pages and I don’t think you can get a sufficient idea about the statements in the book by reading this review only.

        I think many of your comments above regarding people saying that this is not actually what they meant by concept X are spot on, I think this is bound to happen if people read the book, and in the least it teaches us that words in ecology are not taken as serious as in philosophy.

        Maier takes “biodiversity” literally as “diversity of species, functions and so on”, and examines whether it’s morally justified to have this diversity as a goal for moral decisions. The book is really not all about the relationship between diversity and ecosystem services. For example, ES aside, he discusses whether it’s morally justified to assign value to groups rather than individuals, i.e. to cause deaths of individuals in a common species to protect individuals of a rare species (imagine doing this for human races – and yes, Maier does discuss the relation to affirmative action).

        What I meant by straw men is that, unlike Maier, I would say that ecologists use the word “biodiversity” in a much more fuzzy way – its nearly synonymous to “everything that is good and right in an ecosystem”, so it really becomes a tautology that biodiversity is good from their point of view. For example, people would say they protect biodiversity by removing non-endemic species. But what they actually mean is that they preserve the historic state of the system.

        In parts, I found it a problem of the book that Maier insists on examining the statements in the literature under the assumption that words are used in their precise meaning, instead of interpreting them wider. By that, he shows that ecology is sloppy in wording and logic, but it reduces the possibility to examine in detail whether the things that are actually meant by diversity have any merit.

  2. When judging about this book review by Vellend one should consider a recent publication of him “Global meta-analysis reveals no net change in local-scale plant biodiversity over time”.
    I wonder how this book review might compare to a review of, let´s say, B. Cardinale or D. Tilman.

    Anyway, I generally appreciate the discussion about “common assumptions” in ecology, such as biodiversity is, per se, valuable.

    EDIT FROM JEREMY: Jan’s comments here should be read in light of his follow-up comments below, which have now been edited at his request for clarity.

    • Dear Jan,

      I just updated the post to address your concern here, but let me address it directly. Frankly, I’m not clear why the fact that Brad or Dave might review the book differently is relevant here. I certainly hope you’re not trying to engage in proof by authority! Nor am I clear why you think his recent publication in PNAS is relevant; perhaps you can elaborate.

      I recognize that Maier’s book, and Mark’s review, is going to be quite hard for a lot of people to stomach. It’s taking an unpopular position, and it’s suggesting that the majority view may have arisen from confirmation bias. I’m also aware that there are a lot of people who didn’t like Mark’s PNAS paper (though personally I’m not sure why; I’ve read it carefully myself and I don’t see any technical mistakes or wildly oversold interpretations…). So I’m aware that there’s a higher than usual risk that this thread will get overheated and descend into personal attacks and people questioning one another’s motives. It’s for that reason that I actually hesitated a bit before posting on this. But I decided that it was an important enough issue, and interesting enough to me personally, that I ought to post. Plus, there was already discussion happening in other forums. And we’re fortunate to have a great commenting community whom I’ve always been able to trust to have a vigorous debate without the debate descending into personal attacks, proof by authority, insinuations that one should “consider the source” of views with which one disagrees…Let’s all make sure this thread lives up to the standard set by previous threads on controversial topics.

      And just to be clear, I’d have said exactly the same thing if your comment had questioned something by Brad or Dave by insinuating that Mark would have different views.

      • Dear Jeremy,

        thanks for updating your blog post. My concern with a review from Mark Vellend on Maier’s book is caused by questioning his objectivity, and I think a reader of both your blog post and the book review should at least know about the possible limitations of objectivity by mentioning the PNAS article of Vellend et al. 2013.
        But, this concern might be relaxed by your statement that “he is one of the most objective people” you know. I think that a (likely subjective) review from B. Cardinale or D. Tilman may result in more criticism on some points of Maier’s book.
        EDIT: My point is that M. Vellend likely has a different point of view on Maier’s book in comparison with some other ecologists, considering the PNAS article of Vellend et al. 2013. I wonder if a review from e.g. B. Cardinale may result in a review containing more criticism on some points of Maier’s book. For example, Vellend could have been mentioning that the highly diverse tropics provide not only a large source of diseases but also a large source for medicine. But I´m not an expert on this.

        I may repeate my above statement, but, I appreciate the work of Maier and Vellend as following discussions can improve the work of many ecologists.
        So much for the book and the review.

        Just one more word on the Vellend PNAS paper: The research group I´m working in (here in Jena, Germany) wrote a Reply on this paper, and I know of some more Replys from other groups. Sadly, non of them has been accepted by the PNAS editorial (at least from what I know) – so much for starting a discussion on this topic. To be clear, I´m not eager to get a PNAS publication by just writing a small Reply; it´s the discussion on the topic I´m interessted in as my work is on BEF stuff.

        Thanks, Jeremy, for writing this post despite concerns about personal attacks and so on.

        NOTE FROM JEREMY: This comment has been edited at Jan’s request, to clarify his point. Jan was writing in his second language, and his original version has a different connotation to native English speakers than the one he intended. A subsequent exchange of comments between Jan, Brian, and myself has been edited and deleted to remove material arising from this misunderstanding. Apologies to Jan for the misunderstanding, I’m glad there are no hard feelings on anyone’s part.

      • Thank you for the clarification Jan. I’m still not clear why the fact that Mark published that PNAS paper would cause one to question his “objectivity”, at least as I understand that term. But I’m glad you agree that the discussion should focus on the issues rather than speculation about people’s objectivity or motives or whatever.

        I suggest that this comment thread isn’t a good place to engage in discussion of Vellend’s PNAS paper, as that’s not the topic of the post. But the example you raise is one instance of the broader issue of how best to conduct post-publication “review”. We have a recent post on that, and another one coming up, so if you want to discuss that broad issue please do chime in on those comment threads.

        NOTE: Comment edited to remove a bit based on a misunderstanding; see edit to Jan’s comment above.

      • @Jan:
        Re: Mark’s book review not giving an extensive list of, say, pluses and minuses of biodiversity, it’s a one page book review. There are severe space constraints; I’m sure Mark would’ve liked to say much more but couldn’t. Plus, a book review isn’t the place for a comprehensive review of a topic. A book review is just supposed to be one person’s informed reaction to the book, and that’s what Mark’s review is.

  3. Just to pick up on two points you raise:

    “nobody ever talks about all the ecosystem disservices that biodiversity also provides, such as increased disease risk. And how come ecologists never argue for promoting species invasions on the grounds that it would increase biodiversity and thereby enhance ecosystem services?”

    Neither of those are true; recent critical reviews of the ES concept have highlighted “ecosystem disservice” – try googling it and you’ll see what I mean.

    And a number of ecologists have argued that we should embrace the idea of “novel ecosystems”, and the services they provide, based largely on invasive species. In fact, the response to our recent letter in TREE about overplaying the role of honey bees as pollinators boiled down to “let’s have more of them in all ecosystems as they’ll stabilize interaction networks, despite being non-native”. Which is nonsense; but it shows that some ecologists are thinking along those lines.

    Will have to take a look at the book but I suspect that it will irritate me….

    • Hi Jeff:

      Re: “nobody” ever talking about ecosystem disservices, yeah, fair point–”nobody” is too strong a word. But I do think ecologists as a group talk a lot more about the ecosystem services biodiversity provides than the disservices.

      Wasn’t aware of that argument about the role of honeybees as pollinators and whether they should be encouraged to spread and increase in abundance. That’s interesting.

      I get the sense that you’d see Maier as attacking a strawman? That from where you sit, few ecologists actually believe or make the blanket arguments that Maier attacks? Or am I misreading you?

      • Agreed, we leave it to the medical profession to talk about the disservices :-)

        I’d need to read Maier’s book to see what it is he’s attacking. But from what you’ve written it seems that two things are being conflated: the value of “diversity” per se, and the value of “organisms” for providing ecosystem services.

        It’s perfectly possible to have ecosystem service provision by a low diversity of organisms; a forest of just oaks will sequester as much carbon as a forest containing 10 species of deciduous tree, all things being equal. And most of the crop pollination in the UK is being done by a small (but abundant) fraction of the c. 500 species of wild bees and hoverflies.

        But of course the argument is that diversity should help to insure against future losses of species.

  4. I agree with most points here. Many of these claims about biodiversity are either double sided or weaker than commonly acknowledged. Counter claims are not “politically correct”. There are exceptions though: e.g. Ariel Lugo’s work on welcoming alien plants and the new forests they generate. And I myself have highlighted how tropical rain forests may be a plausible source of new pharmaceuticals and cures but they are also a major source of novel pathogens (e.g. see in Ghazoul and Sheil 2010 Tropical Rain Forest Ecology, Diversity, and Conservation Oxford University Press).
    I wonder though if there is a deeper misunderstanding of the word “value” (hard to judge without seeing the book). Value is not an inherent property of an entity but a measure of a relationship between a clear subject and the object of valuation within a context (time and place, or hypothetical scenario). Normally an economic perspective asks what people are (or given some context or knowledge should be) willing to pay. Justifications can be rational or irrational but the value is still a value. I think most conservationists will acknowledge that we value nature because we think it is important due to simple personal beliefs and ethical reasons … economic arguments drawing on ecology and function may in some cases be mustered to support that and persuade others … but economic arguments are not why we ourselves think it matters or why we value it.

  5. The argument that biodiversity can cause disease is not persuasive to me, except in the trivial sense that parasites are part of species richness. Virulence theory suggests that pathogens first become dangerous (in evolutionary terms) when the host organism populations become large, dense and uniform; typically the opposite of what is observed in biologically diverse ecosystems. This is directly connected to the ecosystem resilience concept; while an oak monoculture may sequester as much carbon as a forest of 10+ tree species, it takes a single oak-specific disease to wipe it out. This happens much less easy in the 10+ spp forest.

    That being said, this is a rather basic argument which probably have been argued better elsewhere, and which Maier is likely to cover. I guess I should obtain the book and read it.

    • It sounds like you’re thinking of specialized diseases that only infect a single host. The argument about host biodiversity and disease prevalence ordinarily focuses on pathogens that can infect multiple hosts. And similarly for evolutionary arguments about the evolution of new diseases (you’re not likely to evolve so as to be able to infect a novel host if there’s only one host present). But yes, these are very basic, broad-brush considerations, best to take a look at the book to assess the full argument on this point.

    • Gunnar – My pathogen point concerns human health and the implied +ve value of biodiversity for novel treatments versus the -ve value (taking a people centric view) of novel infections.
      Consider the zoonotic species that jump species to impact humans. Many of these have been major health scares, e.g. Yellow fever, SIV/HIV, dengue, Ebola, Sars, Chikugunya, rabies, SARS, Marburg, leishmaniasis (various), trypanosomiasis (various), oropouche … Of course then there are the malarias, the influenzas… and many many arboviruses (I predict we shall see many new diseases emerge from the species rich wet tropics). The reservoir host(s) is/are often uncertain as there are many options.
      Living in a forest in Uganda we were super aware of the danger of handling sick bats and primates (e.g. re- Marburg and Ebola).
      I think the point is that “biodiversity can cause disease” because there is a huge library of organisms out there some of which can impact us given time. Disrupting forests, hunting, etc. certainly play a big part in the “jump” but the source is biodiversity in a similar way that it is for the pharmacology. If we don’t talk about values that is.
      See for one nice example:

      http://www.scielo.br/scielo.php?pid=S0100-879X2001000100002&script=sci_arttext&tlng=en/

  6. Hi Jeremy,

    Firstly, thanks for posting on this review – I must admit, I have seen previous links to it, but no substantial efforts to really discuss a) the book and b) Mark Vellend’s review (but I see the links you’ve included above the updates). I’m regretful that my initial tweet generated a less measured response because I was not calling into account Mark Vellend’s scientific integrity, but more trying to place his comments in context with his recent research. It’s important to note that the PNAS paper did upset some people, and took a strongly contrarian view to what could be considered a ‘rule’ of ecology, or at least an orthodoxy. More importantly though, without reading Maier’s book I have to be wary of jumping on him or Mark Vellend’s interpretation of the text. I suspect in a debate on a topic as diverse (pun intended) as this no-one is ‘right’ or ‘wrong’. The wonder of the natural world is that rarely things are black and white (unless you’re a Zebra).

    I will say though, that there is strong body of work pointing to the importance of environmental context (and the multiple interpretations that implies) in modulating the influence of biodiversity on ecosystem functioning. For example, a diverse habitat maybe required for a diverse community to maximize its function. Which raises another point – the distinction between an ecosystem function and an ecosystem service needs to be better highlighted. For example, decomposition (a fundamental ecosystem function) can bring about positive ecosystems services (e.g., nutrient cycling), but also potentially, disservices (e.g., greenhouse gas production). Not exactly revelatory. But the net balance of that and whether one considers biodiversity as a positive influence for human needs comes down to values, indeed suggesting valid contemplation by a philosopher.

    In regards to disease dynamics, I have no expertise, but will say that I have the understanding that co-infection can reduce virulence, at least suggesting that the role of biodiversity and pathogens requires greater research. Maier may base his arguments off current knowledge, but there is much we still do not know. We could talk also about sex and genetic diversity, but that might be about something like a red herring.

    Vellend in his review points to the ‘inconvenient empirical observations’ demonstrating that much food production comes from monocultures, or at least low diversity agroecosystems. This is where I might go off the rails (or at least further), and argue that humans have diversified their niche (and the ability to manipulate habitat) to such an extent that they no longer rely on biodiversity (in certain contexts) to provide ecosystem services such as food production (there are numerous examples where humans do rely on biodiversity though, and a diverse habitat!). Humans can hand pollinate plants where pollinators have been lost, and we have machines to plant seeds where dispersers are relegated to roles as vermin. Whether that is ‘right’ or ‘wrong’ is a philosophical matter (and perhaps an economic one as well; there is an opportunity cost if humans have to be pollinators as well as everything else). I’m certain there are flaws to this argument, but maybe that’s the point of the book: let’s start talking about it.

    I suspect network theory and computational approaches might be required to really resolve the diverse outcomes of biodiversity, species interactions, and ecosystems. Anyway, I appreciate the discussion you’ve started, and I know from previous Dynamic Ecology posts that you value the role of the contrarian and diverse views. Just like Hubbell challenged niche theory, Vellend and Maier may be doing the same for the value of biodiversity.

    • Thanks for your further comments Frank.

      Re: your intent to merely Mark’s review in “the context of his recent research”, sorry, but I still don’t follow. And I’m going to pursue this a little bit, not because I’m mad at you (in all honesty, I’m not), but because I do think your passing comment on this actually represents an important mistake. And I have the impression that you’re not the only one making this mistake. So I’m going to take the opportunity to talk about what I see as the mistake here. Again, I’m honestly not trying to pick on you or anyone else. It’s clear from your comment that you want to focus on substantive issues, which is great. But I do think your passing attempt to provide “context” actually is at best a distraction from talking about substantive issues, in ways that maybe you’re not even aware of (?)

      My view is this: Like any piece of writing, Mark’s book review stands or falls on its own merits. His words in that review mean what they mean. Their meaning doesn’t change because of other words Mark has written elsewhere. So far from providing useful ‘context’, references to what Mark has written elsewhere function *only* as an irrelevant distraction at best.

      One of the most common ways for people to fool themselves, to protect themselves from having to engage with evidence and arguments that challenge their current beliefs, is to focus on irrelevancies. Instead of worrying about the evidence and arguments offered by the author, we worry about the motives of the author. Or about how we once disagreed with something else the author wrote. Or about the author’s credentials. Or etc. Everyone, *very much including me*, is sorely tempted to fall into this kind of trap all the time, usually *unconsciously*. The only defense (and it’s a very imperfect defense) is to consciously bend over backwards *not* to fall into this kind of cognitive trap.

      Now in response, you might say, well, I haven’t read the book, so I’m not in a position to evaluate Mark’s review directly. Therefore I can *only* evaluate it indirectly based on inferences like “I didn’t agree with that recent paper of his, so I’ll be a little skeptical of his review”. Or you might say, maybe some others haven’t read the book, so aren’t in a position to evaluate Mark’s review directly. So I’ll help them out by encouraging them to keep in mind that some people didn’t agree with one of Mark’s papers. To which my response is: don’t do that. Don’t ever jump to even tentative conclusions based on that kind of indirect “evidence”, and don’t ever encourage anyone else to do so either. Not when direct evidence is available! After all, if you don’t feel able to fully judge Mark’s review, or the book itself, because you haven’t read the book, the appropriate response surely is to read the book. And until then, to *withhold judgement*. Not to come to even a tentative judgement based on indirect evidence. I mean, why do you *need* to come to even a tentative judgement about Mark’s review, or the book itself, before you feel able to do so? Scientists are the last people who should ever jump to conclusions! Even tentative, provisional ones.

      The only contexts I can think of where it makes sense to “consider the source” are contexts in which two conditions hold: (i) you don’t have and can’t easily acquire the information and expertise needed to evaluate the evidence and arguments, *and* (ii) you *have* to come up with an evaluation rather than simply reserving judgement. For instance, there are many important public policy issues where I don’t have and can’t easily acquire nearly enough information and expertise to come to my own informed opinion on what the best policy is. But yet, I feel like I need to have an opinion, in order to decide how to vote in elections. So I fall back on “considering the source”–I decide who to trust based on considerations like who’s paying them, do I agree with other things they’ve written, etc.

      So while it seems like you didn’t mean much by your passing reference to the “context” of Mark’s PNAS paper and how it was controversial, I hope you can see why even that sort of passing reference worries me. It’s just sooooooo easy for people to fool themselves and fall prey to cognitive biases, especially on controversial issues. We have to be ever-vigilant against that.

      In response to your substantive comments, I agree with you (and other commenters like Jeff Ollerton) that there actually is ecological work on things like the context dependence of biodiversity effects, whether biodiversity really makes much of a functional difference compared to, say, abiotic conditions, whether positive functional effects of biodiversity saturate at really low levels of biodiversity, etc. I guess the question then becomes whether ecologists collectively have paid sufficient attention to that sort of work and given it sufficient weight, especially in their more public pronouncements. I do think there are reasons to worry on that score.

      Also worth noting here that these issues have been raised before. For instance (and this is just one example from memory), I believe Diane Srivastava (?) and colleagues had a review in AREES back in the 1990s questioning suggestions that conserving biodiversity or ecosystem function was all that important for many conservation purposes.

      I should also note that I’m probably among the guilty parties when it comes to overselling the benefits of biodiversity. I have some papers on biodiversity and ecosystem function. Which I wrote to address what I thought were some interesting fundamental/conceptual issues. But in the introductions of those papers, you’ll find the usual boilerplate about how we’re losing biodiversity and that’s a bad thing because it might degrade key ecosystem functions on which life depends. I confess I didn’t think much about that boilerplate, it was just the sort of thing everybody routinely said in order to motivate their biodiversity-related research. At some level I was of course well aware of the flaws and limitations of that argument–but you’d never be able to tell that just from reading the introductions to my papers.

  7. Not having read his book, I gather that Maier is mostly arguing against the perspective that biodiversity is always good, in all contexts.

    I wonder, though, whether he views biodiversity as a site-specific metric. When ecologists discuss biodiversity, don’t we typically mean something site-specific, such as “declines in biodiversity at Site A are bad and increases (or recoveries) of biodiversity at Site B are good (e.g. for ecosystem service X)?”

    Then the arguments mainly become about what suitable baselines are, whether newly-arrived species affect whatever metrics we care about (ecosystem services, site biodiversity ec), and whether eliminating species impacts the metrics we care about. This leads to a lot more context-dependency of how & when biodiversity is to be valued (and also when it may not be related to a given metric).

    Regardless, the point that taking a pro-biodiversity stance and then arguing for it using ecosystem services language may be misconceived is well-taken. E.g. see “Selling out on nature” — Nature 443, 27-28 (7 September 2006) | doi:10.1038/443027a.

  8. This reminds me of a lunch seminar/discussion that Brian ‘hosted’ recently. I hope he’ll chime in with his research into biodiversity trends.

    I’d say that, from a Conservation Biology perspective, there isn’t that much focus on conserving biodiversity per se. A lot of the reserve design work is focused more on representation and redundancy. I’m wary of efforts to target biodiversity by itself for conservation because I’ve seen it used in very questionable ways (i.e. to show biodiversity increases after timber harvest). On the plus side, biodiversity is used as short-hand for conservation of organisms that often get ignored like inverts.

    I guess I’m a bit on the side of ‘biodiversity is the most important thing’ as a straw-man argument. Maybe ecologists are just lagging behind conservation biologists?

    • What do you mean by biodiversity? This is one of the big problems with research into biodiversity, everything gets lumped under one term.

      From my perspective biodiversity can generally be measured richness, evenness, distinctiveness etc and can be measured at a huge variety of scales from genes, to populations, communities, entire ecosystems… I think when we talk about changes to biodiversity we need to be explicit about what we mean. For example ‘deforestation leads to declines in biodiversity’ is a little nonsensical, whereas ‘deforestation leads to declines in species richness’ is a lot clearer.

      When we are looking to link biodiversity to function and services we also need to be clear about what we are talking about and shouldn’t muddy the water by just lumping everything as ‘biodiversity.’

      • This I strongly agree with. Many of the replies assume that biodiversity is just ecosystem services (is this what you mean Jeremy?). Another view is that ecosystem services are a product of biodiversity so biodiversity is justified because is provides ecosystem services. Further, there appears to be problems with describing biodiversity as “richness, evenness, distinctiveness etc and can be measured at a huge variety of scales from genes, to populations, communities, entire ecosystems” as biodiversity becomes basically a bi-word for all of biology. Then any hypothesis that mentions biodiversity such as ecosystem services increase with biodiversity becomes ecosystem services increase with some feature in biology.

  9. Interesting thoughts from everyone here – much appreciated. It was quite a challenge to boil my thoughts on Maier’s book down to one page. One of the reason’s I found the book so compelling was based on a growing discomfort with my own thoughts on the issue, as much as anyone else’s. As a card-carrying nature lover, I would love to be able to argue with great certainty that greater native biodiversity is always the best thing for human well-being, and in the past I was ready with family and friends to trot out the standard arguments. But the more I scrutinized the actual science behind such arguments, the more I got worried that my conclusions had preceded full and dispassionate consideration of evidence. Maier calls us out for this in no uncertain terms. There’s no question that humans often trash nature to our own detriment, but whether or not biodiversity per se is “good” in any particular conservation or management situation depends greatly on the objective (e.g., optimization of a particular ecosystem service), and the answer runs counter to conventional wisdom surprisingly often. As scientists, we have much to contribute to the question of how best to achieve certain conservation and management goals. But we also have lots of personal preferences about what those objectives should be (via the inner nature lover), and to maintain credibility we should probably be very careful to prevent such preferences from influencing the scientific conclusions we draw.

  10. I think this post and the comments it inspired are very interesting and intriguing. Personally, the most intriguing part is the frequent occurrence of words like “good”, “value”, “pluses and minuses” , because I wonder to what extent they should be a part of a scientific discussion at all. Douglas already touches on this issue by discussing that value is not an inherent property of an object and Mark in his last post also hints at these issues. However, they do not go as far as asking whether we should discuss these issues at all.
    As a scientist I am very comfortable with making statements that X leads to Y, but I shy away from stating whether that is “good” or “bad”. I consider that a personal judgement rather than a scientific judgement. I have been regularly involved in discussions about over-fishing, in which case I have always made it perfectly clear that I will not provide a scientific opinion whether a certain management action is good or bad: If it is suggested to eradicate all tuna from the oceans (I guess we are trying hard), as a scientist I feel I can only line out as clearly as possible the consequences of such an action. As a person I might be infuriated by this idea, but when asked for my scientific opinion I will suppress expressing my personal opinion simply to avoid any confusion between scientific and personal arguments.
    The discussion about biodiversity is in my opinion also muddled because of this mixing of scientific and personal opinions (In that respect even the title of Maier’s book is fascinating, because it contains already a notion of “value”). Stating that biodiversity increases ecosystem functions or services is not a solution to the problem either, because that only raises the question why ecosystem functioning or services are so “good”. Why is maximising total biomass or total productivity in a system “good”?
    As a science, ecology is quite full of these kind of “value” judgments and I have the feeling their presence is increasing (consider for a moment the focus on “Earth Stewardship” by our largest representative body ESA). But I seriously wonder to what extent they should be part of our science at all and whether the fact that we do not separate between scientific statements and such “value”-based judgements adds to the sentiment that science is just another opinion.
    I’m quite keen to learn what others have to say about this. I guess my opinion is clear from the above: we should very clearly distinguish between scientific statements and “value” judgements and preferably not express the latter when we are asked for our scientific opinion. Otherwise, I fear it is in the long run going to hurt our scientific credibility.

    • Good point Andre, with which I agree. Though I suspect others won’t–the point you make has vexed ecologists for a long time. I’m thinking of how the Nature Conservancy was founded by ecologists who split from the ESA because ESA wanted to remain a purely scientific organization, much as you describe.

  11. Nice post Jeremy. From what I’ve read so far of Maier’s book (only the first couple of chapters, admittedly), I would really recommend people read it before dismissing his arguments. OK, he seems inordinately pleased with his own cleverness, and has a philosopher’s inclination to choose many long words instead of few short whenever possible; but I really think he has a point. The concepts of both ‘biodiversity’ and ‘value’ are too often vaguely defined in the biodiversity / ecosystem services literature, and a moral philosopher’s perspective is really useful – as he asks, “Is biodiversity similar… to other human beings with regard to its moral implications? Or might biodiversity be more like my old computer – something that has served some set of particular human needs well enough, but that is entirely dispensable when better alternatives present themselves or when my needs and desires change?” These are tough questions, and while it may turn out that Maier is wrong, I think our field will be stronger for having grappled with them. At the moment, I do tend to agree with him that “it is hard to avoid the impression that so many studies investigate biodiversity as an independent variable in ‘objective’ ecological relationships precisely in order to bolster its credibility as the basis for ‘the good’ at which conservation and restoration work then aims.” In other words, we all *know* that biodiversity is valuable, our challenge is to demonstrate this to policy makers, the public, or whoever. But what if we’re wrong…?!

  12. This is getting off the original topic, but it’s an interesting discussion: Philip & Christopher’s comments above imply that there is a single, “right” definition of the term “biodiversity” and that it can only be used in one way. I disagree with this, and I don’t think it the term was ever meant to be used in that sense. My understanding is that it was always meant to be an umbrella term that captured a lot of different aspects of research and practice going on in ecology, biology, nature conservation, etc. Certainly that’s how the early publications used it.

    Personally I’m comfortable with it being widely applied. In fact, when I was promoted to a personal chair I chose the title “Professor of Biodiversity” precisely for that reason: it captures the breadth of what I do professionally in a way that “Professor of Ecology” or “Professor of Pollination Biology” (other possibilities I considered) never could.

    I do, however agree that we need to be precise in defining the way in which we use “biodiversity”, even if (or because) it has a multiplicity of uses. So to take Philip’s example above:

    ‘deforestation leads to declines in biodiversity’ is a little nonsensical, whereas ‘deforestation leads to declines in species richness’

    Agreed, but I would have phrased it as:

    ‘deforestation leads to changes in biodiversity’

    Because actually all kinds of parameters change when areas are deforested, including (sometimes) an increase in species richness (even if it’s the species we don’t want!)

    • Hi Jeff.

      I didn’t quite mean that I think there is a correct way to define biodiversity. It means different things to different people. Which is why I thought when we are setting hypotheses or describing results we should be explicit about which bit of biodiversity we are interested in.

  13. Before I weigh in on this discussion, let me say that I’ve been a skeptic of the field of biodiversity-ecosystem functioning research from its inception. I have repeatedly called out ecologists for making claims about biodiversity’s role in providing goods and services that can’t be substantiated by data. I have been critical of those who extrapolate from small-scale, unrealistic experiments using random species assemblages. And I have also pointed out that biodiversity can, in some instances, be a ‘dis-service’ … reducing goods and services to society. So like Maier and Vellend, I am not adverse to criticizing the field or point out flaws.

    Having said that, I must also say that I find the criticisms levied in Maier’s book, and the criticisms outlined in many of Vellend’s papers and reviews to be extreme and unconstructive. I think both of these individuals repeatedly fail to consider several important points:

    (a) While it is true that many claims about biodiversity are unsubstantiated, there are now >15 meta-analyses of more than 1,700 published papers that shows biodiversity does, in fact, influence the functioning of ecosystems as well as many (not all, but many) of the goods and services they provide to society. Vellend and Maier seem to consistently ignore all of the evidence that shows a role of biodiversity simply because there are some data that show the contrary, or more often, a lack of data to support claims. What kind of logic is that? It strikes me as somewhat illogical to ignore vast amounts of existing data simply because you can find exceptions and incomplete datasets.

    (b) Furthermore, Vellend and Maier will repeatedly point out flaws in the observational and experimental science that lead them to be skeptical of the conclusions. For example, Mark will repeatedly tell you the 500+ experimental manipulations of biodiversity are all ‘too small scale’, ‘too short term’, or ‘too unrealistic’ to draw meaningful inferences about the role of biodiversity. Though I agree with some of his criticisms, I also think it is illogical to ignore vast amount of data simply because you feel the data could have been collected in a better way. One doesn’t throw the baby out with the bathwater just because the baby isn’t perfect.

    (c) I also find it unsettling that Vellend and Maier rarely, if ever, acknowledge the results of studies that are addressing some of our concerns and working to overcome limitations. They don’t acknowledge studies that have shown biodiversity effects grow stronger as studies run longer. They don’t acknowledge studies that have shown biodiversity effects grow stronger for studies performed at larger spatial scales. They don’t acknowledge studies showing that non-random extinctions often reveal greater impacts than random scenarios of extinction. In my view, it is not constructive to criticize an entire field of research, and then fail to update one’s perspective as new studies emerge and the field matures.

    In sum, I am not a fan of how Vellend or Maier characterize the balance of evidence in the field of biodiversity research, as I don’t see much ‘balance’ in their perspectives at all.

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