How is Nature doing? Biodiversity, sustainability, and biomass

Last Friday, I posed the question under what definitions of Nature one can say that it is doing badly, and whether there were other ones under which it was doing fine. I was explicitly interested in how Nature is doing now relative to decades or longer periods past, though of course once one has a definition one can judge future trajectories with it too.

For those who want to cut to the chase, I personally would advocate moving towards a composite index of Nature on this planet, because no single goal would seem to capture what people really think when they talk about Nature. Such indices are already being developed for the oceans (see Yet, I could not find overall indices for world ‘Nature’, so it would seem there is a vacuum there for some organisation to fill. Presumably, as with the oceans, there will be moves under way to create such indices. I think they would be onto a winner.

There were many interesting reactions to the question of how to define Nature and whether it was hence in bad or good shape. One type of reaction was ‘how dare you pose the question’ which I presume is by people who have already decided on the ‘obvious’ answer.

A more serious and recurrent answer was ‘biodiversity’ and there is no doubt that that diversity has been rapidly reducing the last few centuries. Some openly said biodiversity should be the definition and it was also implicitly the answer by all those talking about the great extinctions of the past and the one we seem to be hurtling towards. And just to remind you in case you are wondering, I am not a climate change denialist though I am sceptical that anything but geo-engineering will halt climate change.

Still, I have always been ambivalent about thinking of Nature as ‘biodiversity’ and not just because of the obvious point that surely the state of ‘Nature’  should include some notion of volume and not just variance.

It is not hard to see the appeal of biodiversity as a measure of Nature: the more biodiversity, the more potential for yielding benefits to humanity. Also, the greater the biodiversity, the quicker the recovery would be from any temporary changes in the environment. Perhaps most importantly, the sheer love of variety would have one appreciate more diversity. So if we are to think of ‘Nature’ as a composite thing for which we would want some kind of index to measure its current state by, then biodiversity should surely be in that index. Commensurate with this, I am all in favour of breeding programs for endangered species and plant-seed banks as a means of preserving diversity.

The problem for an economist is that we can engineer biodiversity: if we were to truly take biodiversity as the state of Nature and we would like there to be more Nature, then the obvious question becomes ‘what type of diversity would you like to see’? Given that we have become much better at genetic engineering, the production of Nature would simply end up being a matter of setting enough labs to the task of creating more diversity.

As soon as one puts this kind of logical consequence to proponents of biodiversity, they invariably back-peddle and start to argue that human-made diversity somehow does not count as real. But that is just a cop-out. If one does not want to add to ‘Nature’ by paying for more man-made bio-diversity then clearly diversity is not the be-all and end-all of Nature but at most a part of it.

One can then up-scale the notion of diversity and redefine ‘Nature’ as being about a diversity and richness of habitats, under which definition it is again fairly clear it is not doing so well. The appeal of this alternative definition is much the same as that of simple biodiversity but the upgraded definition is now a bit more impervious to the obvious engineering riposte. It also is much closer to a notion of ‘sustainability’ in that greater habitat diversity more clearly involves a regenerative ability.

With habitat diversity we get closer to what a lot of conservation is about, with the protection of unusual habitats leading us to be careful of pristine environments. Again, it is a definition I would intuitively agree with, though once more it would be the case that if this is truly what we value then we should not be squeamish about setting our labs to work on the question of how to create (or re-create) whole habitats complete with appropriate fungi and bacteria. Of course, we are moving in this direction too, though I personally think we should be much more forthright in this. For the life of me, I can’t see why we should not welcome straightforward engineering in this realm.

A completely different conception of Nature is to define it solely in terms of the services it can provide us humans with, i.e. to define Nature in terms of its usage value. This was of course the definition used in the millennium report on this and by that definition, the state of Nature is ambiguous. For sure, there is no doubt that all kinds of habitats have reduced but they have in the main given way to other habitats, not wastelands (though there are some of those too). It would need some kind of composite index of Nature’s value to tell us whether it has reduced. If we simply think of those services as ‘food production’ then in fact Nature has grown in the last few decades, though perhaps the potential for more Nature has then declined.

Conrad at Troppo furthermore mentioned that if we think of Nature as being about sheer volume of living material or animal mass, then perhaps Nature would not be doing so badly either.

Sheer biomass has a lot of appeal as a measure of Nature. One can try and measure it; it has a democratic feel to it (every ounce of living material is worth the same); it includes us humans as well as any other animal; and one can quite easily weigh different types of biomass more heavily if one feels some things are more natural than others (surely the umpteenth tree is not worth as much as the first elephant!). It also has obvious positive connections to human service value and restorative powers so it partially captures those as well. So if I had to chose a single measure of Nature, I would probably go for biomass, and I was being clever about it I would transform biomass using a continuous CES love-of-variety utility model.

Still, even (transformed) biomass is not ideal because it fails to pick up the advantages of habitat diversity and its connection to usage value is too loose. What would thus be ideal is a Nature Index including biodiversity, habitat diversity, services to humans, and sheer biomass.

Yet, it is interesting to consider the question of whether biomass has in fact been reducing or increasing in the last few decades. Let’s consider that question on Wednesday.

Author: paulfrijters

Professor of Wellbeing and Economics at the London School of Economics, Centre for Economic Performance

8 thoughts on “How is Nature doing? Biodiversity, sustainability, and biomass”

  1. Biomass is dumb; 99% of all life mass is bacteria. We could wipe out out every other vertebrate inhabitant of the planet and still end up with pretty much the same number. It makes ‘whale’ and ‘dead whale’ equivalent, as there’s always going to be something making a meal of ‘dead whale’, which is true about just about anything that doesn’t die in fire and go up in smoke, so apart from burning, it’s not clear to me that biomass can really go down.


    1. So, really we can answer your question sooner. Find out how much fossil fuel we’re burning plus the contribution from thawing permafrost, measure the increase in concentration of CO2 in the air and the oceans, any difference in carbon is biomass increasing or decreasing.

      Actually I quite like Dr Nick’s contribution of Planetary Boundaries.

      As for diversity, I’ll see your ‘create diversity and the lab’ and raise you. Every living thing that has sex increases diversity more in seconds than any human lab can do in six months, but I like your thinking. Bring back the Thylacine I say. 😉


  2. I do not think that it is at all obvious that any measure should include some notion of volume – in fact I think it is obvious that volume/mass/population is irrelevant (except inasmuch as insufficient population implies less diversity).

    The most obvious candidate for a defensible measure is to base it on a notion of information content / order. Once information (as, for example, embodied within the genome and proteome of some individual) has been destroyed, it cannot be recreated – so that is a real loss to the universe. This also applies to the order replaced with disorder when some physical artifact of the natural world is destroyed.

    Your bio-engineered diversity argument does not worry me, either – current genetic techniques amount to either “cutting and pasting” from one genome to another, or turning on or off the expression of a set of genes. This activity does not increase total information content.

    You *could*, instead, create large numbers of new individuals by randomly mutating existing genomes and selecting out the viable individuals – any such viable individuals would represent a tiny increase in information content. However, to offset even the information loss from the extinction of a single species in this way would require a massive devotion of resources – there’s a *lot* of accumulated natural selection that’s gone into making that species what it was yesterday.

    In terms of habitat creation, you are on firmer ground – although the most successful examples in history have been accidental (human cities are after all artificial habitats). Deliberate attempts are usually copies of naturally-occuring habitats – for example artificial reefs.


    1. I find the ‘volume does not matter’ argument very weird. Is not a billion humans more Nature than just 2 humans, even if the billion are genetically speaking merely in between the 2? Would a thousand identical habitats not be more Nature than just 1? If I think of Nature as something to care about then more is indeed better.

      Take the ‘information is all that matters’ argument seriously. How would we create and stimulate maximum information? We’d probably artificially try to set up as many different extreme environments as we could, put fast reproducing bacteria near them and collect the resulting ‘new information’ emerging within adapted bacteria and freeze them. A whole giant freezer full of more ‘information’, is that really what Nature is for you?


      1. If you use genetic diversity as your benchmark – say the genome is a (very)large vector and all individuals are mapped into that space, and diversity is the cumulative distance between each vector and the centre point of all, then a larger population will lead to higher value diversity without any extra data needed. Volume does matter. A bit.

        Your reductio ad absurdum can be played both ways – do we really increase nature if we mass produce giant swimming pools of gelatenous bacteria? Or if we killed every vertebrate animal so that plants have free reign to grow (plant biomass is what, 1000 times that of all animals?)

        Besides bacteria don’t reproduce sexually, they only vary through mutation, so the freezer thing might take longer than you think to produce variation.


      2. Ben,

        Do we produce more Nature if we plant 10,000 more trees of a variety we already have plenty of? Of course we do and our schools do this regularly.


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