Words and Ideas: Commitment, Continuity and Irreversibility 157To sharpen the issues, consider extreme and tragic forms of irreversibility. Per-
haps the best known is the extinction of species. A world without the tiger, white
rhinoceros or panda would be profoundly diminished. Nor is this a question of
only such iconic species, but of a great range that are endangered. The irreversibil-
ity and uncertain risks of GM (genetically modified) crops are another case. Less
recognized is the destruction of rocks. A stark tragedy is the destruction through
quarrying of rocks near Delhi and in and near Hyderabad.^25 These were formed
billions of years ago and have weathered over geological time. Apart from intrinsic
worth, they have (or had before being destroyed) cultural, aesthetic, ecological,
recreational and spiritual value to us humans, giving experiences of place and
beauty, sustaining a diversity of life, and providing for the recreation and fulfil-
ment of rock-climbing. Their destruction is utterly irrevocable. Trees that are cut
can be replanted. Even soil that erodes can be replaced. But with rocks, restoration
is not an option. Once blasted and removed, they are gone. Forever. With a dread-
ful finality.
Reflecting on these biological and physical examples, if we are to assure options
and resources for future generations, irreversibility simply has to be a key concept
embedded in our thinking and informing our decisions and actions and non-
actions. It is then striking that it is not significant in mainstream economic think-
ing. Much attention is paid to risk – ‘the probability or probability distribution of
an event or the product of the magnitude of an event and the probability of its
occurrence’ (Alcamo et al, 2003, p214) and uncertainty, the condition of not being
known or predictable, where the probability distribution is not known (Devereux,
2001, p508), and each has a considerable literature. But irreversibility is less well
developed and less frequently mentioned as a concept. Two standard economics
textbooks – Economics (Begg et al, 2003) and Economic Development (Todaro and
Smith, 2003) – include risk in their glossaries; but neither mentions irreversibil-
ity.
Not only is irreversibility little considered, but conventional economic practice
systematically undervalues it. First, discounting gives low or negligible present val-
ues to distant future benefits or costs (Chambers and Conway, 1992, pp18–19).
Present value has, however, often been taken as a basis for decisions. To correct
this, Zhao and Zilberman (1999) have proposed a new concept of irreversibility
cost, and point out that discounting may encourage a pattern of developing now
and restoring later. This applies, for example, with the high costs of decommis-
sioning nuclear power stations, which in present value terms were very low at the
time of deciding to build them. Irreversibility traps a project or society into having
to pay such costs.
Second, substitutability is invoked, with the idea that technological develop-
ment will find substitutes for resources or services that are depleted, damaged or
destroyed. In this view, depletion and degradation of ecological capital are not
irreversible in the sense that they can largely be overcome by the accumulation of
knowledge and of manufactured and human capital.^26 However, even if techno-
logical substitutes exist or are found, their cost is typically high, limiting access to