B IODIVERSITY AND UNCERTAINTY

Our knowledge and understanding of most species, interactions between species, ecosystems functioning and what roles different species play, is still highly incomplete and full of uncertainties.¹⁹⁵ There is also much uncertainty about the anthropocentric value of different products and services from nature.¹⁹⁶ What complicates it even further is that many species are not even discovered yet. How can we value the services or goods they may supply?¹⁹⁷ In previous chapters we have encountered situations where our attempts to assess the value of other species have been hampered by uncertainty. We will hopefully be able remove some of the uncertainty by more thorough investigations, but we can probably not remove it completely without substantial costs,¹⁹⁸ or maybe even at all. To get a perfect prediction of what will happen in an ecosystem in the long term when we make as fundamental changes as removing a species might not even be possible.¹⁹⁹ The old view of nature as a machine – a clockwork with mechanic precision where a particular intervention necessarily leads to a particular, foreseeable effect – is replaced by a more modern conception of nature as something dynamic and complex, or even uncertain and chaotic.²⁰⁰ We have in other words started to realise that the way nature reacts to our treatment is not completely predictable.

Donna Maher talks about a change of science from a situation where

… prediction of system behaviour was a matter of having enough data, to a 'science of surprise', where chaos and unpredictability are endemic, with stability and predictability the exception.²⁰¹

Sverker Sörlin makes a similar point by referring to chaos theory and catastrophe theory when he tells us that the old fashioned linear models will not help us find out at which

195 Aniansson 1990 p.38,42, Farber 2000 p.s492, Ihse 2005 p.71, Söderqvist 2005 p.78

196 Farber 2000 p.s495

197 Randall 1986 p.85

198 Farber 2000 p.s496, McGarvin 2001 p.25

199 McGarvin 2001 p.25

200 Beltrán 2001 p.4, Herremoës et al 2001 p.193, Sörlin 1991 p.18

201 Maher 1999-2000

point the decreasing ozone layer, or the greenhouse effect etc. will take an uncontrollable catastrophic turn.²⁰² He does not mention loss of biodiversity, but the same reasoning can probably be used here.

One of these nonlinear phenomena that we have to consider when we are dealing with complex things like living beings or ecosystems is (as we have noted earlier), the existence of threshold values.²⁰³ Normally we assume that cause and effect are proportional, and can be described by some linear equation, i.e. that a certain change in the cause leads to a corresponding proportional change in the effect. However, in some situations all or most of the effect takes place when the causation power has reached a certain value – the threshold value. In this type of situation, most changes in the causation power do not have any visible effect at all, but still have the important indirect effect of taking us closer to the threshold value. This climbing closer to the threshold value is in many cases something that takes place invisibly.²⁰⁴ When the threshold is reached, the next change in the causing power – however small – will mean all the difference in the world. Then the up to now only latent effect will suddenly occur all at once.

In our case, it would mean that the disappearance of a single species, or two or three, from an ecosystem might not result in any discernible effects on e.g. the ecosystem services.

This might go on for a while but when a threshold is reached, the results could be dramatic.

Anne and Paul Ehrlich use an analogy about a person who pops rivets from the wings of airplanes. He sells the rivets for 50 cents each and he defends himself by pointing out that:

I’ve already taken 200 rivets out of this wing, and nothing has happened yet. Lots of planes fly with missing rivets. They build a lot of redundancy into jet aircraft, partly because they don’t completely understand the materials and stresses involved, so nobody can prove that taking another rivet out will weaken the wing too much.²⁰⁵

As we saw in the previous chapter, decreasing redundancy might have unwanted consequences. One consequence that we touched upon was that we might be approaching a threshold. Both the story about the water filler and the story about the rivet popper are illustrations of this.

202 Sörlin 1991 p.255

203 Daily 2000 p.335. Clarke 1995 p.41, Herremoës et al 2001 p.193, McGarvin 2001 p.25, Norton 1986:1 p.123 (Clarke talks about them as “jump effects”.)

204 This is not always the case though. Sometimes it is indicated by something else than the effect we are worried about (and do not see any trace of yet).

As Bryan Norton points out, the assumption of the ‘rivet popper’ that the absence of any accident so far is an indicator that the risk of an accident in the future is very low, would be true if we were talking about a series of independent events. The problem is that we are not. For every rivet he pops, there are fewer rivets left, which means that the constitution of the plane is constantly getting weaker. The same goes for species: For every species that goes extinct above the speciation rate, there are fewer species left, and the ecosystem – even the global system – is weakened.²⁰⁶

This is typical for threshold effects. Every change in the input takes the system closer to the threshold even though the effect is not noticeable until we reach the threshold.

Margareta Ihse extends the collection of “threshold-analogies” with an analogy about a hammock where the species are the threads of the fabric that will hold us up for a while, but bursts when the fabric gets too thin.²⁰⁷

This is a very good analogy of ecosystems as well as of the circulation of nutrients etc.

in nature. They can be described as a web with many intertwined threads. This gives the system a certain amount of stability but we do not know when the web gets too thin to uphold its function. It also illustrates that the resisting power of nature that is due to the redundancy in the systems is never a guarantee against severe changes. It holds back – and hides – the changes for a while and lulls into a false sense of security, but it does not stop the change forever and when it occurs all the change occurs at once.

The Ehrlich analogy points at an important difference between the natural disappearance of species and the high extinction rate we are facing at the moment due to anthropogenic interventions: Normally the species that go extinct are replaced by other species just like lost rivets in an airplane are replaced by new rivets.²⁰⁸ At the pace by which species are disappearing today, the species cannot be replaced fast enough however and we face a net loss.

There is one important difference between the analogy with the rivets and the loss of species however, and unfortunately, this difference makes the species loss much more problematic than the loss of rivets. New rivets can be taken from the storeroom and the old ones can be replaced by human maintenance personnel. Species on the other hand are replaced by evolution. Instead of being taken from a storeroom, they evolve from the genetic

205 Ehrlich et al 1990 p.95

206 Norton 1986:1 p.122, Norton 1987 p.68

207 Ihse 2005 pp.70f

208 Ehrlich et al 1990 p.96

basis that already exists in the existing species. This tells us that in order to replace lost species with new species that have a better chance of survival, we need above all a large selection of genes. I.e., we need a large biodiversity, and that is precisely what we are losing.

The non-linear aspect can be brought one step further and form another argument to consider: Sometimes a very small change in the input can have a very large effect on the output. If there are effects like this in ecosystems, it must be a very strong argument indeed for extra caution about all interventions in the ecological systems – including interventions that contribute to the extinction of species.

Furthermore, if we take a closer look on the evolutionary process, we will find that one of its inherent features is that it has no predetermined direction. It is not the case that the individuals of a species always get bigger or faster or more intelligent. The direction in which the evolution takes a certain species depends on its environment and on chance. The environment changes all the time, and what “remedy” that evolves in a certain species as an

“answer” to a particular change in the environment depends on what its gene pool happens to have in store, and on which re-combinations and mutations that happen to take place. Which of these “remedies” in turn that eventually are favoured by natural selection, depends not just on one single aspect of the environment in which the species live, but on the total selective pressure that the environment puts on the species. If rabbits (Oryctolagus cuniculus) become faster, foxes (Vulpes vulpes) have to evolve too, but not just in relation to the rabbits. If they evolve a quality that makes them better rabbit hunters but also makes them less resistant to cold or easier prey for the lynx (Felis lynx), they will loose out in the evolutionary game anyway. All species are in fact at any given moment subjected to pressure of many different types from a large number of different directions, and the sources of the pressure are also in their turn subjected to pressure of many different types from a large number of different directions – including from the species they are exerting pressure on. If we were going to calculate the direction of evolution for the fox, we would have to consider the selection pressure that is placed on the fox by both the lynx and the rabbit, as well as all other species that interact with the fox as well as all the non-living forces of nature. The rabbit and the lynx and the other species evolve too however, and that has to be taken into account. The fox is putting both the rabbit and the lynx under selective pressure just as they do with the fox, but that is not all. The lynx not only eat foxes but also rabbits so we have to look at the pressure they exert on each other. The lynx also eat other prey though and the rabbit is not just hunted by the fox and the lynx. It therefore does not just evolve in a way that helps the

rabbits cope with the threat from these predators, but also as a result of how the golden eagle (Aquila chrysaetos) evolve since they eat rabbits too, etc. The pressure from the lynx and the golden eagle will inevitably also affect what options the genes of the rabbit has when it comes to “dealing” with the threat from the fox and so on. Then we have to put the result we get for the rabbit back into our equation for the fox together with the results from other prey species for the fox, and so on and so forth – and while we have done that the whole scenario has already changed. In short, we would have a problem that is infinitely more difficult to solve than the “three body-problem” in physics.

What this tells us is that we simply cannot know for sure what will happen in an ecosystem in the long run when we make such a radical alteration as changing the species composition.

Changing the species composition can be done in different ways. It can be done e.g. by causing a species to go extinct as we are discussing here, or by putting in a new species that was not there before (but that may well have the result in other species disappearing).

The best literary description of the latter is probably Michael Crichton’s book “Jurassic Park”.²⁰⁹ In this book, species of animals and plants that lived more than 65 million years ago are resurrected and placed in a present day environment. As we know, it did not work out very well in spite of the guarantees from John Hammond and his bio-engineers. This was of course just fiction. We do not know what will happen in a situation like this, but the point of the story was just that: We do not know, because we cannot know. It is impossible to predict the results from such a project, and therefore we should be more cautious. To recreate pre-historic organisms is quite extreme, but many of the interventions we make are almost as extreme, and as we saw above, our possibilities of foreseeing the results are limited. The best and most frightening illustration in the book is probably the absolute confidence by which Mr Hammond and his staff guarantee the safety of the arrangement. (What is particularly frightening is how easy it is to recognise this unshakable confidence in many people in the real world.)

There are many real-life examples of how we have intervened in nature and ended up very surprised over the results. The rabbit explosion in Australia and the drought catastrophe in Sahel in Africa are both described as examples of catastrophic situations caused by our ignorance about ecology.²¹⁰ A well-known example of how human beings have deliberately tried to engineer nature to suit our purpose by taking away a species from the system, is the

209 Crichton 1991 passim

wolves that where hunted virtually to oblivion in North America in order to protect both farm animals and game animals (or to be more precise, to protect human farmers and hunters from the competition). This resulted in an explosive increase in the number of deer, which in turn caused a lot of damage to the ecosystems. It also had a negative economic effect on the human population since it destroyed the grazing for domesticated animals such as sheep.²¹¹

All the examples above confirm the problem of predicting what will happen in an ecosystem as a result of human encroachment. The lesson that seems to emerge from this section is that we will probably never reach a situation where we have enough information to make a fully informed decision as to which course of action is the most rational from an anthropocentric instrumental point of view. We therefore need some kind of strategy for how to handle the uncertainties that we cannot get rid of. In the coming sections we will try to find such a strategy, and we will in particular take a closer look at one that has recently become very popular.