The concept of critical natural capital emerged as a compromise between two extreme positions within sustainability research, i.e. strong sustainability and weak sustainability. Generally spoken, it signifies the part of the natural capital that performs important ecosystem services that cannot be substituted by other types of capital, such as human-made or social capital (de Groot, Van der Perk, Chiesura, & van Vliet, 2003; Dietz & Neumayer, 2007). Paradigmatic examples include essential ecosystem services, such as freshwater resources, climate regulation and fertile soils (UNEP, 2005a). It is this importance for the quality of life and the survival of humans that makes critical natural capital such an important objective of sustainability. Critical natural capital thus represents the part of the natural environment that ought to be maintained in any circumstances in favour of present and future generations, i.e. is part of the minimal necessary conditions of sustainability.
Concept of critical natural capital
Yet conceptual controversy and confusion on the term critical natural capital is immense, as numerous scientific disciplines and societal groups bring their own perspective in valuing nature. It is indeed highly debatable what makes natural capital ‘important’, ‘irreplaceable’, and therefore ‘critical’. In other words, it is controversial which measure would be appropriate to reflect or mirror ‘criticality’. In the following sections I will expand on some conceptual issues regarding the term “critical natural capital” and propose an own framework how to conceptualize and estimate the criticality of natural capital (cf. also Brand, 2009). Yet before turning to these conceptual issues I give a short introduction on the historical development of the term.
The concept of critical natural capital has been developed by Turner (1993) following capital theory in economics (cf. for the term “capital” Ekins et al. (2003)). It gained some attention through the recent EU-project CRITINC (cf. Ekins, 2003; Ekins, et al., 2003) and has been applied to several EU-countries, such as France (Douguet & O'Connor, 2003) and the UK (Ekins & Simon, 2003).
The concept of critical natural capital is obviously based on the concept of natural capital, often understood as any stock of natural resources or environmental assets that provides a flow of useful goods or services, now and in the future (MacDonald, Hanley, & Moffatt, 1999; Pearce & Turner, 1990). The term “natural capital” has been criticized for its reductionistic and utilitarian connotations (Chiesura & de Groot, 2003), praised for its terminological strengths (Dobson, 1996) and continues to stimulate a debate about its accurate conceptual intension and extension (de Groot, 2006; Ott & Döring, 2004). It is widely used to signify a myriad of components (e.g. resources, biodiversity, fertile soil, ozone layer), properties (e.g. ecological resilience, ecosystem health, integrity) and dispositions (e.g. regulative or assimilative capacities). Natural capital is thus a multidimensional meta-concept for a plurality of interrelated and heterogeneous stocks that perform various functions and services for human society (Aronson, Blignaut, Milton, & Clewell, 2006; Chiesura & de Groot, 2003; Ott & Döring, 2004).
Regarding the multidimensional character of natural capital, it is not surprising to find conceptual confusion and controversies about “critical natural capital” (MacDonald, et al., 1999; Turner, 1993). This is due to the existence of different perspectives under which natural capital can be considered as critical, as different disciplines and standpoints bring different conceptual frameworks to value ecosystems (Chiesura & de Groot, 2003). The identification of criticality is thus a genuine evaluative task. The decisive question is: ‘critical for what and for whom?’ (de Groot, et al., 2003).
Based on an extensive review of all the relevant literature I have ordered the perspectives on criticality along different domains, which together build the basis for a comprehensive framework of critical natural capital. At least six domains may be distinguished under which natural capital is evaluated as critical. (Note that there is some unavoidable overlapping among some of the described dimensions.)
- Socio-cultural: natural capital can be important, crucial or vital for a particular social group, as it provides the context for human society in terms of nonmaterialistic needs, e.g. health, recreation, scientific and educational information, cultural identity, source of spiritual experience or aesthetic enjoyment (Chiesura & de Groot, 2003; Kazal, Voigt, Weil, & Zutz, 2006).
- Ecological: people value natural capital as critical for its ecological characteristics, such as the degree of naturalness, high biodiversity and uniqueness (de Groot, 2006; de Groot, et al., 2003), for instance.
- Sustainability: this domain refers to the debate of weak vs. strong sustainability. Natural capital is viewed as critical in a functional sense as regards to human well-being if it is non-replacable with other types of capital (Dietz & Neumayer, 2007; Neumayer, 2003; Turner, 1993). Good examples are life-securing ecosystem services, such as the provision of food, raw materials or drinking water.
- Ethical: a loss of natural capital can be morally disadvantageous in that moral values are being violated (Dietz & Neumayer, 2007). For example, from the standpoint of sentientism the preservation of higher developed animals, e.g. bears and beavers, would be prima facie regarded as critical (Haider & Jax, 2007).
- Economic: the loss of natural capital can bring about very high economic costs. These costs can be assessed by the full spectrum of methods for monetary valuation (de Groot, 2006). On the other hand, the preservation of critical natural capital may have considerable opportunity costs (Doria, Migliavacca, Pettenella, & Roson, 2000).
- Human survival: natural capital becomes obviously critical when without it human life would not be possible (Dobson, 1998). Examples are the provision of drinking water, flood regulation or fertile soils.
Consequently, definitions of critical natural capital are manifold, as specific domains of criticality are being stressed. Some definitions refer to one domain of criticality only. For instance, Turner's (1993, 11) definition “[t]he constraint [of critical natural capital] will be required to maintain populations/ resource stocks within bounds thought to be consistent with ecosystem stability and resilience” is ecological, whereas the definition put forward by Douguet and O'Connor's (2003, 237): “natural capital which is responsible for important environmental functions and which cannot be substituted in the provision of these functions by manufactured capital” stresses the sustainability domain. Alternative definitions try to include a higher amount of criticality domains, as for instance, the definition proposed by Dietz and Neumayer (2007, 619): “we may ‘ring-fence’ as critical any natural capital that is strictly nonsubstitutable (also by other forms of natural capital), the loss of which would be irreversible, would entail very large costs due to its vital role for human welfare or would be unethical”.
Each of these definitions refers to specific domains of criticality only and can thus be criticized as partial and incomplete. There is the need for a more comprehensive approach to criticality. Here I consider natural capital to be critical if it applies to at least one of the six domains of criticality, i.e. the socio-cultural, ecological, sustainability, ethical, economic or the human survival domain. In this conception criticality comes in degrees. Criticality is dependent on (a) the amount of significance within one domain of criticality (e.g. the socio-cultural importance, the ethical value, the economic costs), (b) the amount of domains under which the natural capital is valued (i.e. the more domains the more critical) and (c) the weighing of the different domains. Hence, different parts of natural capital can have various degrees of criticality. Certainly, in this conception of criticality, a certain stock of natural capital is also valued as critical if it is valued in one domain of criticality only, and this has been criticized above as being incomplete. However, the important thing to have in mind is that the criticality of natural capital should be evaluated referring to different dimensions, even if one domain is the most important (e.g. human survival, ethical concerns, immense economic loss). It is also important to note that criticality is in most cases context-specific (de Groot et al., 2003), as it is related to certain standards of living and human values that may change over time.
In addition, it is worth mentioning that the controversy in defining and measuring what stocks of natural capital are critical is not a scientific dispute only but refers to genuine evaluative judgements. It thus requires sound collaboration of academia, legitimized decision-makers and the overall public within transdisciplinary processes, which take into account the conflicts and possible balance of the different interests present in human systems (Scholz, 2010; Scholz, Lang, Wiek, Walter, & Stauffacher, 2006).
An extension of the framework described above means to stress the ecological precariousness of a certain stock of natural capital and to boil down the discussion on critical natural capital to two criteria: “importance” and “degree of threat” (de Groot et al. 2003). The criterion “importance” is in this conception reflected by the six domains described above, whereas the criterion “degree of threat” explicates in how far a certain stock of natural capital is prone to a qualitative shift to another ecosystem state, which is characterized by a fundamental different overall functioning and structure and an entirely different provision of ecosystem services. It can be shown that the degree of threat is inversely proportional to and measured by the degree of ecological resilience of a given ecosystem providing a certain stock of natural capital (Brand, 2009).
In such a way the conservation of critical natural capital can be regarded as a primary objective of sustainable development and its estimation in concrete cases represents an interesting and crucial research topic for sustainability science (cf. Schultz, Brand, Kopfmüller, & Ott, 2008). It might be of assistance as a conceptual tool to identify the “planetary boundaries” as a safe operating space for humanity (Rockström, et al., 2009).
This article has been improved by the valuable comments made by Laura de Baan, Marco Morosini (both ETH Zurich, Switzerland), Marius Christen (Basel University, Switzerland) and Timo Kaphengst (Ecologic Institute Berlin, Germany).
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