Words and Ideas: Commitment, Continuity and Irreversibility 159views of citizens. These include public inquiries, citizens’ panels, citizens’ juries,
consensus meetings and mediation.
Issues around irreversibility became clearer in 2002 in discussions about con-
cepts for the MA (Millennium Ecosystem Assessment). The MA is an ambitious
project to understand better the relationships between ecosystems, ecosystem serv-
ices and human well-being. Members of the multidisciplinary group of 51 authors
met four times to evolve the conceptual framework^27 published as Ecosystems and
Human Well-being: A framework for assessment (Alcamo et al, 2003). This defines
concepts relevant to this discussion (ibid, pp208–216). Irreversibility is ‘the quality
of being impossible or difficult to restore, or return to, a former condition’. Revers-
ibility is related to resilience – ‘the capacity of a system to tolerate impacts of drivers
without irreversible change in its outputs or structure’. Thresholds are ‘a point or
level at which new properties emerge in an ecological, economic or other system,
invalidating predictions based on mathematical relationships that apply at lower
levels... Thresholds at which irreversible changes occur are especially of concern to
decision makers.’
In the MA’s conceptual framework, values are seen to bear heavily on decision
making where thresholds and irreversibility are or may be involved. In the process
of evolving the framework, values were much debated, both as intrinsic – the value
of someone or something in and for itself, irrespective of its utility for someone
else, and as ecosystem services to human well-being, classified as provisioning, regu-
lation and cultural. Cultural values were recognized as spiritual and religious, rec-
reation and ecotourism, aesthetic, inspirational, education, sense of place and
cultural heritage (Alcamo et al, 2003, p5).
A recurrent theme was keeping options open for future generations. For this,
option value was defined as:
... the value of preserving the option to use services in the future either by oneself
(option value) or by others or heirs (bequest value). Quasi-option value represents the
value of avoiding irreversible decisions until new information reveals whether certain
ecosystem services have values society is not currently aware of (Alcamo et al, p213)The precautionary principle, embodied as Article 15 of the Rio Declaration (United
Nations, 1992, p3; see also Harremoës et al, 2002) applies here. This is the man-
agement concept stating that in cases:
... where there are threats of serious or irreversible damage, lack of full scientific cer-
tainty shall not be used as a reason for postponing cost-effective measures to prevent
environmental degradation.Despite all of this, and the way it underlies much of the precautionary principle,
irreversibility remains an underdeveloped concept.^28 Further steps are needed to
distinguish types, degrees and sequences of reversibility and irreversibility. One
approach is to classify changes as clusters according to two dimensions: causes,