Mar 17, 2010

Year of Biodiversity: only for cute animals and plants?

International Year of Biodiversity LogoThe United Nations declared 2010 to be the International Year of Biodiversity. This sounds great, let's celebrate and protect the variety of life on Earth! We must learn more about current (and past) biodiversity and the impact that human activities have on the distribution and abundance of organisms. Also, we should explore any effective ways to protect biodiversity, if only because it benefits us.

However, it strikes me as short-sighted that most biodiversity advocates seem to care only about "the cute organisms" (cute by most human standards, I guess); that is, a few particular animals and plants. But... for Pete's sake, life on Earth goes well beyond a few vertebrates, trees and corals! Surprisingly, the true diversity of life is not obvious at all in the writings of most biologists, conservationists or environmental scientists when discussing biodiversity and its protection.

I know, I know -- when a clear message is to be delivered to the general public, you cannot be comprehensive. If you can mention only a couple of examples for endangered species, you better go for the much-like-us mammal, or the colourful bird, or the pretty tree or flower. Most of us can easily sympathize with a chimpanzee (that is, really, almost one of us) or with many animals: they have faces, with two eyes and a mouth, and it's hard not to see part of our own reflection there. We often show emotional responses also to trees, flowers or grasses (even mushrooms). So, when explaining the importance of biodiversity to a general audience, sticking to the cute guys might be the wise choice.

But how is this topic treated inside the scientific community? Well, in general, I don't see much difference. When biodiversity is discussed -- in general terms -- in scientific articles, editorials or websites, the focus is again on certain plants and animals that can be seen by the unaided human eye (that is, macro-organisms). By contrast, microbes are hardly ever referenced, if at all.

Why are microbes not even mentioned most of the times? Why are some particular organisms (let's call them "the cuties" for short) the focus of research and protectionist efforts? I can think of a few possible answers:

1 - The cuties, among all the living beings, might suffer the highest risk of extinction.
2 - Although there are other organisms at higher risk, the cuties are perhaps more important (in some way) either for the preservation of particular ecosystems or for human well-being.
3 - Our current knowledge of life diversity might be very limited, and is focused on particular organisms because of historical and technical reasons.

I guess that most scientists and many learned people would agree with me that answer number 3 seems about right (but if you think otherwise, please leave a comment). Actually, it seems that we know very little on the matter. Scientists are starting to agree -- I think -- on a broad definition of biodiversity. But the field faces (at least) two huge challenges. First, there are many organisms living on (and inside) this planet that we haven't met yet, and our estimates of how many species are awaiting discovery are little more than educated guesses. Second, although biodiversity can be measured at various levels, it's often understood as referring to the number and relative abundance of different species. And deciding if two organisms belong to a single species, or to two different ones, can be really hard. Moreover, the difficulty in agreeing on species definition depends greatly on the type of organism it applies to: whereas this issue causes some serious troubles when studying cuties, it appears almost insurmountable when trying to define microbial species. Why is this so? Well, I'm not getting into this here, but let's say that the species concept was originally created and crafted for the cuties, and microorganisms just don't fit into such clothes.

However, even lacking a suitable species definition (to the embarrassment of microbiologists), we can confidently say that the microbes are much more diverse than the cuties. This diversity is shown at different levels: genetics, biochemistry, ecology... You can find microbes almost everywhere, and often in amazingly high numbers. No matter if you count individuals or you measure biomass: microbes are the (silent?) majority. Some microorganisms are essential not just for the preservation of particular ecosystems but for the continuity of life on Earth as we know it (and when I write "life" I mean "life", not just "cuties"). Under any non-human-centred point of view, life is microbial -- with a few exceptions, yes.

So, just to recapitulate... Some animals and plants appear to be on the brink of extinction because of human actions, and it doesn't seem a good idea to let them go. However, we don't know how many types of organisms are out there, or how many of them are endangered by our activities, and we don't understand the long-term effects of the extinction of any particular life form. Yes, more research is definitely needed.

But we do know that life is incredibly diverse and mostly invisible to the human eye, and that the cuties are not even the tip of the iceberg. So, any serious research or scientific communication on the diversity of life should include (in my opinion) some mention to microbes, the main actors on this movie -- at least we should acknowledge our ignorance! Microbes play key roles in nature: shouldn't we worry about the preservation of microbial diversity?

Don't get me wrong: I don't want any cuties to become extinct. But I think that scientists can do a much better job when discussing biodiversity.

Further reading:

If you find the topic of this post interesting, you must read the following excellent articles written by Sean Nee, University of Edinburgh, UK (articles can be downloaded from the author's website):

- The great chain of being. Nature (2005) 435: 429.

"Our persistence in placing ourselves at the top of the Great Chain of Being suggests we have some deep psychological need to see ourselves as the culmination of creation."

- Extinction, slime and bottoms. PLoS Biology (2005) 2(8): e272.
"There is an old Chinese curse: ‘May you live in interesting times.’ According to those who know about such things, we live in a momentous time, the time of the Sixth Mass Extinction! But most of us do not feel at all cursed. Because, in fact, the Sixth is quite different to the previous Big Five—no-one would notice this one if we were not repeatedly reminded of it by ecologists."

- More than meets the eye: Earth's real biodiversity is invisible. Nature (2004) 429: 804-805.
"We are still at the very beginning of a golden age of biodiversity discovery, driven largely by the advances in molecular biology and a new open-mindedness about where life might be found. But for this golden age to be as widely appreciated as it should, our view of the natural world must change — as radically as did our view of the cosmos when we began looking at it with technologies that allowed us to see more than can be seen with the naked eye."

- Beyond the tangled bank (pdf). This manuscript seems a slightly longer version of More than meets the eye: Earth's real biodiversity is invisible. Interestingly, it includes many references that were not incorporated into the published article.

I also recommend a thought-provoking article by Maureen A. O’Malley & John Dupré, University of Exeter, UK:

- Size doesn’t matter: towards a more inclusive philosophy of biology. Biology and Philosophy (2007) 22, 155-191.

NOTE added on April 17, 2010:
A Letter has just been published by Andrew Beattie and Paul Ehrlich in Science, highlighting what The Missing Link in Biodiversity Conservation is:
"the many millions of species within the numerous phyla of microbes and invertebrates, which represent perhaps 95% of total species and genetic biodiversity."
The authors propose to deliver a new message to the public:
"a new message, one we would like to label "production biodiversity": By protecting microbes and invertebrates, we also protect the primary industries upon which we all depend."

I agree!

Related links:
- (Added April 20, 2010) A commentary on the same subject has been published by Mercè Piqueras in her blog, La lectora corrent (in Catalan): La biodiversitat invisible.

- (Added June 23, 2010) See Dear New Scientist by Ed Rybicki, who reminds us that "the greatest part of the biodiversity on this (and probably any other) planet is viruses."

- (Added August 19, 2010) Preserving endangered species – of gut microbes, by Grant Jacobs. Or the need to preserve the human gut microbes found in ancient rural populations.

- (Added September 11, 2011) Bacteria & archaea don't get no respect from interesting but flawed #PLoSBio paper on # of species on the planet, by Jonathan Eisen.

- (Added September 11, 2011) Don’t forget to count microbes, by David Hooper & Bonnie Bassler.

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