Moral Justifications for a General Measure of Biodiversity?
We have argued that large-scale conservation decision-making would benefit from agreement on a general measure of biodiversity, one that is not tied to particular projects or contexts. We have set out a group of broad categories of measurement strategies with the aim of determining whether one of these might furnish an appropriate general measure. In this section, we set out a similarly broad brush taxonomy of philosophical justifications for the conservation of biodiversity with the aim of determining whether any of those available might provide a justification for conservation based on a general measure of biodiversity and hence might provide us with a basis for inference about the nature of such a general measure. We will argue that the best justification is one that respects the plurality of human and non-human interests in biodiversity as well as uncertainty about how best to secure those interests and about future changes both in the environment and in human affairs.
Philosophical justifications for the conservation of biodiversity come in many forms but all such arguments fall into one of four categories.
The idea that biodiversity has intrinsic value is enshrined in the Convention on Biodiversity. It is also a central tenet of deep ecology (Naess 1986). Despite its common currency, intrinsic value is capable of multiple interpretations which causes considerable confusion in moral reasoning (O'Neill 1992 p. 119). At least two interpretations are plausible in the current context.
One is the idea that biodiversity has intrinsic value in the sense that it has value over and above its instrumental value. This interpretation is further dependent on what we count as 'instrumental'. If we tie instrumental value to narrow economic purposes, then there seems to be considerable non-instrumental value in biodiversity. If we tie it to a broader set of psychological benefits (provided by recreation, aesthetic appreciation etc.) then the domain of non-instrumental value seems correspondingly smaller and more difficult to characterise.
A second interpretation is that biodiversity has intrinsic value in the sense that it is valuable independently of the valuations of valuers. It does after all seem that the biosphere would remain a locus of value even if some selective extinction event caused the demise of humanity or even the extirpation of all species capable of reasoning about value. But value in this sense seems almost impossible to quantify precisely because it cannot be tied to evaluative judgements made by economic actors or by environmental stakeholders. The best we seem to be able to say is that some people, when asked, assent to the existence of such value.
Intrinsic value is controversial as a justification for the conservation of biodiversity for two reasons. Firstly, there is philosophical controversy about whether such forms of value exist (Norton 1984, p. 145). Secondly, as it is independent of human projects and human values, it is unclear how it should be measured and hence, how it should be conserved. There seems no way in principle of choosing between variety of ecosystems, variety of species, variety of form and function or variety in genetic make-up etc. as loci for biodiversity's intrinsic value. On the other hand, if intrinsic value is only a justification for the conservation of biodiversity in the very broad sense (set out at the end of section “Measures we rule out”), that will leave us no further along the path in the project of understanding or employing a practical general measure of biodiversity.