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Planet of the Arthropods


I’m on the radio! Skeptically Speaking asked me to talk a little bit about insect conservation, in order to round out an interview with the author of Rat Island. (I haven’t read the book yet, but it looks pretty fascinating.)

I mostly discussed the 2012 report “Spineless”, published by IUCN (The International Union for Conservation of Nature). You might recognize IUCN as author of the Red List, the definitive international list of species that are at risk of extinction.

Why should we care about a bunch of squishy boneless animals?
Because invertebrates make up EIGHTY PERCENT OF ALL MULTICELLULAR SPECIES ON EARTH. They truly are the “little things that run the world.” The IUCN report suggests that 20% of those species are at risk. Little things going away is a big deal.

The report itself is fairly accessible to the lay reader, and includes lots of data, citations, and lovely photos of what we will be missing if we don’t start paying attention. Download and read the report here.

The topic I discussed on the radio was ecosystem services–the stuff we get for free simply by living on earth:

“The Millennium Ecosystem Assessment – a four-year United Nations assessment of the condition and trends of the world’s ecosystems – categorizes ecosystem services as:

  • Provisioning Services or the provision of food, fresh water, fuel, fiber, and other goods;
  • Regulating Services such as climate, water, and disease regulation as well as pollination;
  • Supporting Services such as soil formation and nutrient cycling; and
  • Cultural Services such as educational, aesthetic, and cultural heritage values as well as recreation and tourism.”

For some reason, I ended up talking about poop and waste removal more than other ecosystem services, but insects also make up a major part of food chains all over the world. Birds and fish eat them. People eat them. They pollinate our crops and feed the world. Bugs are damn important.

We also talked a little bit about pest control services that intact ecosystems provide. For example, a 2009 study found that low-diversity cropping systems–think thousands of acres of corn and soybeans and nothing else–had 24% fewer predators.

We lose ecosystem services when we lose biodiversity.

graph of terrestrial invertebrate conservation status

To give you a sense of just how big the problem of species loss is, check out this diagram about terrestrial invertebrates from the IUCN report. This includes insects, spiders, and all the other spineless things that live on land.

You can see from this that 38% of the species in the IUCN database are already extinct or endangered. Thirty. Eight. Percent.

An additional 20% of species are listed as vulnerable to extinction.
OVER HALF of the species that are in the terrestrial invertebrate IUCN database are at risk of extinction or already gone!

What’s that grey category labeled “DD”? “Data Deficient.” Species are classified as Data Deficient on the IUCN Red List if there is inadequate information to evaluate their extinction risk. Of the species with a listing for IUCN, we don’t know enough about 17% of them to assign a conservation status.

Here’s another way of looking at that. This is how IUCN organizes their categories of extinction risk, from high to low:

IUCN category diagram

How many species is the IUCN diagram of terrestrial invertebrate conservation statuses based on? 3,623 species.

How many species of insects and spiders are there, that we know about? Over a million.
How many species of insects and spiders do we estimate actually exist, that are not included in this diagram? Over 5 million.
They don’t show up; we don’t even know enough to include them as “Not Evaluated.”

Chapter One of the IUCN report has the title “The Unraveling Underworld.” Yes. It is unraveling.
I can’t tell you what the consequences of species loss will be, but I can tell you I am sure it won’t be a good thing.

In the interview I mostly focused on how these changes will affect humans economically. We live in a time when utilitarian value is king; and when people are out of work and having trouble making ends meet, it’s really hard to argue that we should save a bug because it’s pretty.

But the truth is we just don’t know.
We don’t know which insects are the important ones. We don’t know which species is the one that when we lose it, things fall apart.

I think Aldo Leopold said it best:

“The last word in ignorance is the man who says of an animal or plant: “What good is it?” If the land mechanism as a whole is good, then every part is good, whether we understand it or not. If the biota, in the course of aeons, has built something we like but do not understand, then who but a fool would discard seemingly useless parts? To keep every cog and wheel is the first precaution of intelligent tinkering.”


Addendum: In response to some rather heated comments, I have edited this post to make it very clear that I’m talking about multicellular organisms. Sorry to be dissin’ the bacteria and protists. Also, link to source of these numbers
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    • That image is from the IUCN report. So, linking to it in a discussion of the report makes sense to me. If you don’t like the image, take it up with IUCN.

      BTW, they are talking about MULTICELLULAR animals and plants in that report. Which is why protists and bacteria are ignored. Also, if you actually listen to the radio show, I am careful to say “multicellular.”

      • BTW, they are talking about MULTICELLULAR animals and plants in that report. Which is why protists and bacteria are ignored.

        Okay. What about fungi? There are about 75,000 species of multicellular fungi. That’s more than the total number of vertebrate species.

        Also, if you actually listen to the radio show, I am careful to say “multicellular.”

        Good. You might want to correct your blog post where you say, “Because invertebrates make up EIGHTY PERCENT OF ALL THE SPECIES ON EARTH.”

        • Cripes. In a number that could go up to 8 million, why do you even care about a couple of *percentage* points on an *estimate* of total species one way or the other? We are two PhDs specialists arguing over how many extinct species can dance on the head of a pin.

          If I was publishing a paper in a peer reviewed journal, then fine, bring the hard numbers and critique. But what I am doing is trying to get people who are not specialists to be interested in an important issue. Your snark is a great example of why a lot of scientists don’t even TRY to do science outreach. No matter what I do, it wil be wrong.

          If I work on getting more people to know something about insects and spiders without 100% accuracy in terms of specialized terminology and significant figures, that’s a problem for you. If I use tons of specialized terminology and qualifications, then that’s a problem for my target audience, who will turn off that radio fairly quickly. (What’s a eukaryote? What’s a fungus? What’s the line between multicellular and unicellular? What about slime molds?).

          The American news cycle runs on 60 second news bites. Blog posts are usually 500 words or LESS. Internet users spend 33 seconds on a web page, on average. I think it’s more important to be in the game than sit on the sidelines and snark.

          You want to do the math, fine. Add in the fungi to the multicellular organisms, and then come up with an estimated percentage. Show me how you got that updated number, and I’ll update this.
          And don’t forget to tell IUCN, since their extensively referenced publication is the source of the numbers I’m using here.

          • Here are the top three criteria in good science education and good science journalism,

            1. Accuracy
            2. Accuracy
            3. Accuracy

            Here’s how I would have written your article.

            Title: There are lots of arthropods on Earth

            Nobody knows exactly how many species there are. There may be millions of species of bacteria and other small organisms. But among the big multicellular species, arthropods, especially insects, rule the roost. There are more known arthropod species, by far, than all plants, fungi (mushrooms etc.), and other animals combined.

          • Here are the top three things that get non-scientists irritated with some scientists:

            1. Pedantry
            2. Self-righteousness
            3. Arguing a useless point for no reason

          • Right. So you haven’t actually addressed anything I said, and you haven’t actually used any numbers. Clever.

            I’m sorry you feel that way. I was trying to make an important point; namely, that your emphasis on arthropods is misleading. You may think that this is a planet of the arthropods but that’s just a personal opinion. I’m with Stephan J. Gould on this one. We live in the age of bacteria …. always have. There are probably more species of bacteria on this planet than eukaryotes and bacteria dominate by total number and total mass. That’s also a personal opinion but one that can be supported by accurate facts.

            I would like the general public to be more aware of the importance of bacteria and protists. I would like to correct the general misconception that animals are more important than other species.

            In the long run, I’d also like to teach the general public that the way we define species can be a problem because it can be quite arbitrary. That’s an important part of your article. Just what is a species and how much diversity is actually at risk if we lose a species of beetle on some tree in the Amazon? Is it as important as losing African elephants or silver maple? Should we worry if a species of diatom goes extinct because the ocean is warming? How about a species of bacteria?

            I didn’t use any numbers in my version because we really don’t know what those numbers are. I think that’s more scientifically accurate that using a number (e.g. 80% of all species on Earth) that we know is wrong, and very misleading. You may think this is “clever” but I think it’s “accurate.”

          • Missing. The. Point.
            I wasn’t asked to speak about the species concept. I was asked to talk about an critical report on invertebrate conservation.

            I use a percentage on purpose; that conveys a *proportion* which is relatively similar, even though our understanding of the “real” numbers changes constantly. I can’t cover everything in all its nuance.

            I had 10 minutes and I did something with it to advance general public knowledge of invert conservation, within the constraints of the medium. Rather than inaccurate or incomplete, I prefer to think of it as narrow.

            Your 10 minutes of fame have been used to….?

          • The point is the numbers don’t matter. The numbers are not accurate, are never going to be accurate, and while trying to get more accurate numbers even more species will go extinct. Even if they were accurate it wouldn’t matter. The problem is habitat loss. Preserve the habitat and you preserve what is in the habitat, along with the dynamics between species that are context dependent.

            The point is, what species are “important” is unknown and unknowable until they are understood in context with the rest of their environment.

            An analogy I like is that the natural environment is like a library, where the organisms are books of information in that library. The libraries are being bulldozed to make way for a parking lot. How do we decide which books to try and save without reading them? Pick the ones that have pretty pictures on the cover? Pick the thick ones? Pick the ones in a language you understand? The ones that have the most copies? The fewest copies? The ones printed in pink?

            Unless you know, any selection is arbitrary. The environment is likely a small world network that exhibits percolation. That is all of the organisms interact through relatively few degrees of separation. The problem is that highly diverse small world networks are robust, until they lose diversity and drop below the percolation threshold. Then they collapse. The percolation threshold is a critical point, so it is not approached linearly, it is approached exponentially.

            The problem with nit-picking the minutia details of numbers of species it that it lets non-scientists say: “Those scientists don’t agree on what is important. Lets slash and burn this forest so we can make money growing GM soybeans.”

          • Yes Laurence, she was talking about you. And seriously, you really don’t want to start with Marilove. She will release the Kraken of Feminist Scorn. It won’t be pretty.

            I’m not sure I agree with her here–I think you’re just being generally pedantic. It’s pretty much the way you seem to operate, regardless of gender.

  1. Well, I’m glad Laurence A. Moran could save me from such dreadful inaccuracy. I feel much better informed. Now I know that there are fewer…or more…fungi…or arthropods…something something multicellular organisms.

    So, yeah, thanks for clearing that up.

  2. In case anyone wants to know more about where all my (and IUCN’s) numbers came from for species diversity, they are mostly from this review paper:

    Which is fairly readable–especially for a peer reviewed journal :)

    What we know and don’t know about Earth’s missing biodiversity
    Scheffers, et al Trends in Ecology & Evolution 27, 2012.
    Estimates of non-microbial diversity on Earth range from 2 million to over 50 million species,
    with great uncertainties in numbers of insects, fungi, nematodes, and deep-sea organisms.
    We summarize estimates for major taxa, the methods used to obtain them.

  3. Super interesting report, thanks for pointing to it! Am I being slow, or why are the percentages on the donut chart not proportional? For example, 7% is almost the same size as 24%, which is smaller than 17%. That threw me quite a bit (and made it look like a smaller proportion of species are endangered than actually are). I know it’s not your chart, just curious about interpreting it.

  4. BTW, just to make Larry and the Pedants (actually, that’s an awesome band name) happy, I have amended the post.
    I went back to the paper that was the source of my numbers, added in their upper estimate for fungi, and….still get about 80% species that are inverts. I am happy to amend the post to make it clearer that I was talking about MULTICELLULAR organisms, which I have done.

    I still think they are missing the point, though. To argue that the estimates we make in our research are meaningless is to argue that we then can’t talk about them. There are two different things going on here:

    1. What is the actual number of species (which I’m happy to correct and discuss)

    2. How should we talk about things which, because of the nature of science, we will never have an exact number for? (which I think he totally doesn’t get)

    Arguing that I shouldn’t use any numbers is the same argument that is made by climate change denialists to dismiss decades of research. “You don’t know for sure!”

    Nope, I don’t know the firm numbers for sure. Probably never will. But I do know *proportionally* the abundance of different kinds of life on earth; and talking about that publicly in a way that motivates people is important to me.
    Not to you? Fine!
    Don’t do it my way.
    But don’t get in my way either.

    • Oh for…..Larry is now claiming my statement “don’t get in my way” is a threat.
      Just to be 100% clear: it’s not a threat, it’s a request for him to stop showing up, being pedantic, and wasting my time. Frankly, it never would have occurred to me that someone would think that was a threat.

      What the heck he thinks an imaginary blue insect-woman on the internet would threaten him with I am a bit curious about, though.

  5. All Larry had to say was “Great post, Bug. I agree that loss of biodiversity is a big problem, and I think a similar or even better case could be made for the importance of micro-organisms.”

    A good discussion could have followed.

    Instead of which, we now know for sure that Larry is an epic blowhard and as such his pronouncements are suspect.

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