What is 'biodiversity'?

Professor Jeff Ollerton explains what is meant by the term 'biodiversity...


Ever since I set up the Biodiversity Blog in 2012 I’ve had it in mind to write a post asking the question “Just what is “biodiversity”?”, but have never quite got round to it, there’s been too many other interesting and important things to write about on here!  This week over at the Dynamic Ecology blog Brian McGill has beaten me to it with a really interesting post entitled:  Biodiversity and pizza – an extended analogy leading to a call for a more multidimensional treatment of nature.
I’m not entirely sure that the pizza analogy works, it’s a little tortuous, but none the less the post is provocative and interesting, and has generated a lot of comments.  I strongly recommend it.
In the interests of recycling, and because the readership of my blog only overlaps partially with that of Dynamic Ecology, thought I’d restate a few things that I brought up in the comments to Brian’s post (but this certainly won’t substitute for going over and reading it yourself”.

One of the questions that Brian asks is:  “Is biodiversity a useful term or has it outlived its usefulness?”  It’ll come as no surprise to readers that I like the word “biodiversity”: I used it for the title of my blog and for my professorship, because it captures a lot about what I value in the natural world, and because it’s a term that I’ve (professionally speaking) grown up with. To my mind it is an umbrella term that can mean different things to different people; some see this as a disadvantage but I think that, as long as we qualify precisely what we are referring to, using “biodiversity” in a loose way is not a problem. Perhaps an appropriate analogy is with politics: if someone describes themselves as a “conservative” or a “socialist” or a “liberal”, those terms cover huge internal variation and political scope, but it’s not a problem because it broadly describes the beliefs of that individual.
As an instance of when “biodiversity” may not be a useful concept for nature conservation, Brian gives an example of salt marsh, often areas with rather low species diversity, as being of low priority for conservation because they are poor in “biodiversity”.  But this ignores the fact that all of the “official” definitions of biodiversity explicitly include diversity of habitats/communities/ecosystems/biomes in a defined geographical area.  For example the United Nations Convention on Biological Diversity defines it as:

“the variability among living organisms from all sources including, inter alia, terrestrial, marine and other aquatic ecosystems and the ecological complexes of which they are part; this includes diversity within species, between species and of ecosystems.” [my emphasis]

Thus destroying an area of salt marsh may indeed result in few species being lost, but it would be a significant loss of biodiversity at that higher level of community/ecosystem, if a region has only salt marsh, woodland and grassland in it: in essence you’ve lost one third of your biodiversity because you’ve lost one third of your habitats.

Something that’s occurred to me over the last couple of days of reading comments and thinking about the questions that Brian posed is that “nature” and “biodiversity” are not actually synonymous at all. When people say they like “being in nature” or they “value contact with nature”, what they are usually saying is that they enjoy landscapes, seascapes, changes in the weather, being out of doors, etc., things which are not strictly part of what we understand as “biodiversity”.

Likewise, “protecting the environment” includes a whole set of non-biodiversity related questions and actions such as air and water quality, wastes management, sustainable use of resources, etc., much of which may not directly affect biodiversity at all.

“Biodiversity” has a specific meaning, as the definition above shows, even though that meaning can be broadly defined. Which sounds like a contradiction, but it’s not – and brought to mind the title of the Led Zeppelin fanzine: “Tight But Loose”*.  Biodiversity as a concept and as a field of research and action involves so many different types of stakeholder (ecologist, botanist, zoologist, artist, conservationist, activist) that (as I said) it provides a useful (loose) umbrella.  Problems only occur when people use different tight definitions and talk past one another.

The other aspect to Brian’s post is around the pros and cons of valuing ecosystem services, which is a much bigger argument in some ways, and I’m going to point readers to two blog posts, one recently from Steve Heard which I think is a very nice, concrete example that captures a lot of the uncertainties that Brian describes:
https://scientistseessquirrel.wordpress.com/2015/08/04/invasions-beauty-and-ecosystem-services-a-conundrum/
The second is one of mine from last July related to the value of valuing nature, which was prompted by the Costanza et al. update paper:
https://jeffollerton.wordpress.com/2014/07/27/how-do-we-value-nature/
These are fascinating discussions that will run and run, I have no doubt.

*I’m found of bringing musical examples into these blog posts :-)


This blog post was first published here.