The Earth is covered by five atmospheric layers, composed mainly of nitrogen and oxygen, but also of other gases. In the stratosphere, the second lowest of these layers, a high concentration of the gas ozone (O₃) absorbs most of the sun’s ultraviolet radiation, which, unfiltered, would be most harmful to biological organisms on the planet’s surface. The planetary boundary on stratospheric ozone is, therefore, concerned with the ability of this ozone layer to filter UV radiation. This ability is measured in Dobson Units (DU), which is the concentration of a gas in a column of air. To determine the ozone concentration, imagine taking out all the ozone in a column of air over a given area, creating standardized conditions (of temperature and air pressure) and checking how thick this layer of pure ozone would be (European Environment Agency 2023). Under these conditions, 100 DU are 1 millimetre, which is the equivalent of a stack of 10 sheets of writing paper. The planetary boundaries framework takes the pre-industrial Holocene baseline of 290 DU as a reference and, assuming a range of uncertainty of less than 5 per cent of this baseline, sets the limit at 276 DU. In 2023, the actual value was 284.6 DU, making the ozone boundary one of three that have not been crossed (Richardson et al. Reference Richardson, Steffen and Lucht2023: 5). 220 DU or less is considered an ozone hole, which, contrary to its name, is not the complete absence of ozone in an area, but a concentration so depleted that it does not absorb enough UV radiation (European Environment Agency 2023).

Of all the planetary boundaries, stratospheric ozone depletion stands out because it is associated with an oft-repeated success story in international environmental politics. In the mid-1980s, scientists discovered a hole in the ozone layer over Antarctica and identified groups of halogenated hydrocarbons as the cause of stratospheric ozone depletion. Back then, many of these gases were found as chlorofluorocarbons, or CFCs, in everyday items such as refrigerators and air conditioners. Alarmed, the global political community moved quickly to negotiate and ratify the ‘Vienna Convention for the Protection of the Ozone Layer’ (signed in 1985, entered into force in 1987) and the ‘Montreal Protocol’ (signed in 1987, entered into force in 1989). In essence, the treaties set out a process by which substances defined as harmful to stratospheric ozone are phased out and the resulting burdens are shared equitably. The Vienna Convention and the Montreal Protocol were the first international environmental treaties to be signed by all member states of the United Nations. Furthermore, this ozone regime has proven to be effective, as stratospheric ozone concentrations have increased. Against this background, Rockström et al. (Reference Rockström, Steffen and Noone2009: 12) concluded that ‘[o]n balance, the case of stratospheric ozone is a good example where concerted human effort and wise decision making seem to have enabled us to stay within a planetary boundary’.

This narrative has been challenged on epistemological and ethical grounds. Grundmann (Reference Grundmann2006), for example, stresses that the scientific consensus was not as great as the subsequent success story makes it appear. Despite initial scientific uncertainty, decision-makers recognized the moral importance of the ozone hole for human survival and acted anyway. Gareau (Reference Gareau2013) points out that the ozone regime follows a neoliberal logic. As a result, it struggles to respond adequately to questions of global justice.

In their respective contributions, Louise du Toit and Christine Winter add to and transcend these critiques. While recognizing the pioneering nature of the ozone regime, they raise ethical questions about the nature of its success. Louise du Toit stresses the importance of creating political institutions with the mandate and capacity to protect morally relevant goods such as the ozone layer. However, du Toit also raises the issue of ‘problem-shifting’ in the context of the ozone regime. Such problem-shifting occurs when the successful resolution of some moral or empirical problems within the regime’s legal framework creates other problems outside the scope of that framework. She goes on to explain the tensions that arise when contested ethical principles, such as the precautionary principle or the principle of sustainability, need to be specified by legal systems. She critically discusses the narrow utilitarian and anthropocentric moral bias of the ozone regime, which fails to assess the full extent of the problems associated with the ozone hole.

Writing from a relational and anti-colonial perspective, Christine Winter advances an approach to justice that seeks to truly grasp planetary relations. Winter argues against thinking of ozone merely as a bounded and delimitable molecule, as the planetary boundaries framework does. Instead, she argues for understanding and relating to ozone in all its natural relationships with living and non-living matter. She then asks what moral rights and obligations arise in and through these relationships. Winter also points to the colonial implications of planetary boundaries in general and ozone in particular. In her view, the concept of planetary boundaries provides an argument for enclosing and ‘colonizing’ a common good. In doing so, it creates the right for some people to use and pollute the stratosphere at the expense of others. Instead, Winter argues for ‘an anticolonial planetary justice [that] proposes a planet on which a life sustaining planetary net of overlapping (local) relationships are the subject of justice’.

3.1 Introduction

Stratospheric ozone, or ozone in the stratospheric layer of the atmosphere, plays a crucial role in absorbing the sun’s ultraviolet (UV) radiation. Destruction of stratospheric ozone allows UV radiation, primarily UV-B, to reach the Earth’s surface. Excessive UV-B radiation can cause skin cancer and cataracts in humans, stunting in plants, and harm to animals integral to the marine food chain (Nanda Reference Nanda1989: 489–90). In recognition of the severe and irreversible effects of UV-B radiation on human health and ecosystems, Rockström and colleagues identified stratospheric ozone depletion as one of the nine planetary boundaries (Rockström et al. Reference Rockström, Steffen and Noone2009a, Reference Rockström, Steffen and Noone2009b; see also: Steffen et al. Reference Steffen, Richardson and Rockström2015).

Stratospheric ozone depletion is one of the few planetary boundaries for which a relevant international law regime – consisting of the Vienna Convention for the Protection of the Ozone Layer (1985) and the Montreal Protocol on Substances that Deplete the Ozone Layer (1987)Footnote ¹ – is readily identifiable; and it is widely considered to be one of the most effective international environmental law (IEL) regimes to date. However, the implementation of the ozone regime has had the effect of shifting problems (Kim & van Asselt Reference Kim, van Asselt, Morgera and Kulovesi2016), thereby creating new, unregulated problems. Furthermore, based as it is on principles such as the principle of sustainable development and the principle of permanent sovereignty over natural resources, the ozone regime is human-centred, and concern for the protection of ozone is arguably linked to its value to humans. While several concerns discussed in this chapter could potentially be addressed by ‘tinkering at the margins’ (Kotzé Reference Kotzé2020: 77), this would not address the underlying values and principles of the ozone regime (which underlie international environmental law more generally: see, e.g., Garver Reference Garver2019; Kotzé & Kim Reference Kotzé and Kim2019; Kotzé et al. Reference Kotzé, Du Toit and French2020); and it is argued in this chapter that broader shifts are required in order to be able to respond the types of challenges being faced in the Anthropocene (Crutzen & Stoermer Reference Crutzen and Stoermer2000; Steffen et al. Reference Steffen, Crutzen and McNeill2007), a new geological epoch, in which humans have become ‘geological agents’ (Oreskes Reference Oreskes, Dimento and Doughman2007: 93; see also Raworth Reference Raworth2014; Moore Reference Moore2016).

The chapter first briefly outlines the international law regime for ozone depletion. The section following highlights various socio-ecological impacts and injustices that arise from the implementation of the ozone regime. Thereafter, the chapter begins to explore how values underlying the ozone regime could potentially evolve in order to address these types of concerns and highlights the importance of shifting away from the human-centred and utilitarian values that underlie the ozone regime and IEL more generally.

3.2 The International Regulation of Stratospheric Ozone Depletion

Chlorofluorocarbons (CFCs) were invented in 1928 as a safer (non-toxic) and more stable alternative to other substances, such as sulphur dioxide and ammonia, for use as home refrigerants (Sinclair Reference Sinclair, Andersen and Sarma2002: 4).Footnote ² Their use on a large scale began in the 1930s (Goyal et al. Reference Goyal, England, Sen Gupta and Jucker2019: 1), and, by 1985, total CFC production exceeded one million tonnes. Of note, per capita consumption of CFCs was 10 times greater in developed countries than in developing countries (Gillespie Reference Gillespie2006: 21). While there was growing concern regarding the increasing presence of CFCs in the atmosphere and their potential role in depleting stratospheric ozone (Molina & Rowland Reference Molina and Rowland1974), there was also considerable uncertainty throughout the 1970s and early 1980s regarding the causes of ozone depletion (with many trying to attribute it to natural causes) as well as the risk that ozone-depleting substances (ODSs) actually posedFootnote ³ (DeSombre Reference DeSombre2000: 49). There was also disagreement over whether a precautionary approach should be followed, or whether conclusive evidence of ozone depletion should first be required (Gillespie Reference Gillespie2006: 152–57).

It was thus significant that the Vienna Convention was agreed to in March 1985. The negotiation process – with regard to both the Vienna Convention and the Montreal Protocol (agreed to two years later) – has been described as ‘particularly impressive’ since negotiations were carried out and agreement reached ‘under conditions of uncertainty, both over the existence and extent of environmental harm and the costliness of taking action to mitigate it’ (DeSombre Reference DeSombre2000: 49). Parties to the Vienna Convention, in the Preamble, noted the potentially harmful impact of the modification of the ozone layer on human health and the environment and indicated their determination to protect human health and the environment from adverse impacts resulting from such modification.

In 1987, the same year in which the link between CFCs and ozone depletion was conclusively established (Sinclair Reference Sinclair, Andersen and Sarma2002: 22), the Montreal Protocol was concluded. Parties more explicitly recognized that emissions of certain substances can deplete the ozone layer and they resolved to control the emission of such ODSs ‘with the ultimate objective of their elimination’ (Montreal Protocol: Preamble). Significantly, the Montreal Protocol introduced control measures for the phase-down of ODSs. Initially, only CFCs and halons were regulated by the Montreal Protocol as these were the only substances that had been identified as being ozone-depleting. However, over time, more substances were identified as being responsible for ozone depletion (Gillespie Reference Gillespie2006: 164; Roberts Reference Roberts2017: 221), and they were accordingly also brought under the control of the Montreal Protocol through several amendments (articles 2A–2J). The Montreal Protocol now covers 114 chemicals in 10 chemical groups, including hydrochlorofluorocarbons (HCFCs), carbon tetrachloride (CTC), and hydrofluorocarbons (HFCs); and it provides for the near-complete phase-out of the substances under its control.

These substances are used in various applications, including air conditioners, refrigerators, and fire extinguishers, and as aerosol propellants and fumigants (DCCEEW 2018). It is notable that many of the substances controlled under the Montreal Protocol are also powerful greenhouse gases and have global warming potentialsFootnote ⁴ (GWPs) hundreds to thousands of times greater than that of carbon dioxide (WMO 2018: Table A-1).

The ozone regime takes specific account of the special needs and circumstances of developing country parties (Vienna Convention, Preamble; Montreal Protocol, Preamble and article 5) and includes several mechanisms in this regard, including delayed compliance with the Montreal Protocol’s control measures (article 5(1) and article 5(8 bis)–article 5(8 qua)) and the allowance of a certain amount of production of controlled substances to ‘satisfy the basic domestic needs’ of developing country parties (articles 2D–2J). Furthermore, in 1990, the Montreal Protocol was amended to provide for the establishment of a financial transfer mechanism (article 10); and the Multilateral Fund – which provides funding to developing country parties to assist them in complying with their obligations under the Montreal Protocol – was established in 1991. This Fund is managed by an Executive Committee, which has equal numbers of Article 5 (developing) and non-Article 5 (developed) country parties. There is also a double majority voting system, in terms of which decisions require a two-thirds majority vote, which represents a majority amongst developed and developing country parties. On this basis, it has been argued that the Montreal Protocol has given effect to the principle of common but differentiated responsibilities (Gonzalez et al. Reference Gonzalez, Taddonio and Sherman2015: 124–25).

More generally, the Montreal Protocol is the first international treaty to have been universally ratified (Godin-Beekmann et al. Reference Godin-Beekmann, Newman and Petropavlovskikh2018: 331); and it has been highly effective in addressing its central concern. Indeed, it was described by former United Nations Secretary-General Kofi Annan (Environmental Investigation Agency 2017) as ‘[p]erhaps the single most successful international agreement to date’. Rockström et al. argue that ‘[o]n balance, the case of stratospheric ozone is a good example where concerted human effort and wise decision making seem to have enabled us to stay within a planetary boundary’ (Reference Rockström, Steffen and Noone2009a: 12). Nevertheless, the implementation of the ozone regime has given rise to several concerns, which are now turned to.

3.3 Concerns Arising from the Implementation of the Ozone Regime

First, and more narrowly, several concerns arise due to ‘gaps’ in the ozone regime (discussed in detail in Du Toit, Reference Du Toit, Kulovesi, Yamineva and Recio2023). For example, ‘production’ is defined so as to exclude controlled substances that are used entirely as feedstock to produce other chemicals (Montreal Protocol, article 1(5)). This means that harmful substances, such as CFCs and HCFCs, may continue to be produced in order to manufacture other substances, including plastics (Andersen et al. Reference Andersen, Gao and Carvalho2021), which are associated with their own adverse socio-ecological impacts (see, among many others, Galloway & Lewis Reference Galloway and Lewis2016; Azoulay et al. Reference Azoulay, Villa and Arellano2019; Hamilton et al. Reference Hamilton, Feit and Muffett2019; Whitchurch Reference Whitchurch2019; Revell et al. Reference Revell, Kuma, Le Ru, Somerville and Gaw2021).

Furthermore, the Montreal Protocol is focused on phasing out substances that are highly ozone-depleting, which are then replaced by substances that are less ozone-depleting – without regard being had to other adverse impacts. Indeed, ‘alternative substances’ are narrowly defined in the Vienna Convention as ‘substances which reduce, eliminate or avoid adverse effects on the ozone layer’ (article 1(4)). Following the phase-down of CFCs and HCFCs, the production and consumption of HFCs increased significantly (Roberts Reference Roberts2017: 224). While HFCs are largely not ozone-depleting, they are powerful greenhouse gases and some HFCs are thousands of times more powerful than carbon dioxide (WMO 2018: Table A-1). Increasing HFC emissions were therefore contributing to climate change. This was a classic example of problem shifting, which ‘occurs when a solution for one problem backfires and generates one or more new problems at different times or locations’ (Kim & van Asselt Reference Kim, van Asselt, Morgera and Kulovesi2016).

Significantly, in 2016, parties agreed to the addition of HFCs to the list of substances controlled by the Montreal Protocol (UNEP 2016). Consequently, HFCs are being replaced by other substances, including hydrofluoroolefins (HFOs), which while having low ozone-depleting potentialsFootnote ⁵ (ODPs) and low GWPs, degrade to produce trifluoroacetic acid (TFA) and ozone. TFA is a ‘persistent toxic chemical’ (Montzka and Velders Reference Montzka, Velders and Krummel2018: 2.4), and its presence has been detected in humans; plants, including crops consumed by humans; aquatic environments; and in the Arctic region (Pickard et al. Reference Pickard, Criscitiello and Persaud2020: 2). For its part, ozone is a greenhouse gas and pollutant at ground level and contributes to more than one million pollution-related (human) deaths per year. Ozone is also toxic to many plants and contributes to significant crop losses (Climate and Clean Air Coalition n.d.), which has implications for, at the very least, human health and well-being. While their long-term impacts are not yet clear (Montzka and Velders Reference Montzka, Velders and Krummel2018: 2.34), it has been argued that HFOs ‘cannot be regarded as overall sustainable alternatives’ (De Graaf et al. Reference De Graaf, Elsner and Hoffmann2021: 9). These examples demonstrate that there is the potential for problem shifting to arise again in the future. However, these new problems – created through the implementation of the ozone regime – would fall beyond the regulation of the ozone regime.

At a deeper level, various values and principles underlying the ozone regime specifically, and international law more broadly, are problematic, and possibly underpin the types of concerns identified earlier. It has been argued generally that international environmental law is incapable of responding to the types of socio-ecological crises that are being experienced in the Anthropocene, including because it is anthropocentric, and it does not embrace an earth system perspective (Kotzé & Kim Reference Kotzé and Kim2019, Reference Kotzé and Kim2021).

The ozone regime was established in the 1980s, and, while it has developed, it remains human-centred. Its concern, reflected throughout, is with humans first and then the environment. Furthermore, the Vienna Convention in its Preamble specifically recalls the ‘pertinent provisions’ of the Declaration of the United Nations Convention on the Human Environment (the Stockholm Declaration), particularly ‘principle 21, which provides that “States have, in accordance with the Charter of the United Nations and the principles of international law, the sovereign right to exploit their own resources pursuant to their own environmental policies”’. Although the principle of permanent sovereignty over natural resources is linked to decolonization and addressing the North–South divide (Atapattu Reference Atapattu, Alam, Atapattu, Gonzalez and Razzaque2015: 80), it clearly promotes the exploitation of natural resources (Kotzé et al. Reference Kotzé, Du Toit and French2020). More generally, the primary concern of the Stockholm Declaration is with preserving the ‘human environment’ due to its utility to humans and it does not recognize the intrinsic value of nature. The Declaration emphasizes that ‘[e]conomic and social development is essential for ensuring a favourable living and working environment for man and for creating conditions on earth that are necessary for the improvement of the quality of life’ (United Nations 1972: principle 8) and, furthermore, that ‘[o]f all things in the world, people are the most precious’ (United Nations 1972: Preamble). The Stockholm Declaration is clearly focused on enhancing the quality of human life, even at the expense of non-human life. The explicit recalling of the provisions of the Stockholm Declaration suggests that the ozone regime, too, takes a utilitarian approach to the environment.

Furthermore, while the ozone regime is concerned with phasing out substances that deplete the ozone layer, it is not concerned with limiting the activities that rely on these substances. Taken together with its recalling of the provisions of the Stockholm Declaration, the ozone regime arguably supports ‘sustainable’ development, which has been described as an ‘epistemology of mastery’ (Adelman Reference Adelman, Grear and Kotzé2015: 22) and as ‘so conveniently malleable that it enables its proponents to mask the negative socio-ecological impacts of relentless growth-driven development promoted by states and corporations’ (Kotzé & Adelman Reference Kotzé and Adelman2023: 3). Problematically, sustainable development is central to environmental law and governance (Kotzé & Adelman Reference Kotzé and Adelman2023; Schmidt Reference Schmidt2022).

As the world warms, demand for air conditioning and refrigeration (the primary applications of HFCs) will increase and coolants will become increasingly important to health, well-being, and life itself, particularly in developing countries. However, coolants such as HFCs contribute to global warming which will, in turn, further increase the demand for coolants (the ‘cooling paradox’ (IISD 2021)). Such uses should be contrasted against the use of refrigeration for the transport of food to wealthy countries and the use of air conditioning in private motor vehicles. Recent research shows that almost 20 per cent of greenhouse gas emissions from the food sector are generated by the transport of food across and between countries, with wealthy countries making a disproportionately large contribution to the problem (Li et al. Reference Li, Jia and Lenzen2022). In addition, temperature-controlled transport is required for vegetables and fruit which further increases their food miles emissions. Low-income countries were responsible for generating just 20 per cent of food transport emissions (Malik & Li Reference Malik and Li2022). Such ‘luxury’ uses are not questioned by the ozone regime.

To the extent that the ozone regime implicitly supports continued ‘sustainable’ development (and the continued use of substances that are potentially harmful to earth system components), socio-ecological harms and injustices will likely continue. Adelman points to the challenges of reconciling the welfare of humans and the planet under mainstream forms of development (Adelman Reference Adelman, French and Kotzé2021: 68); and others argue that achieving equity (between humans) within planetary boundaries will require reduced consumption in the North (Steffen & Stafford Smith Reference Steffen and Stafford Smith2013; Hickel Reference Hickel2019). It is thus increasingly recognized that alternatives to mainstream forms of development (such as sustainable development), which are centred around growth, are required (see, e.g., Hickel et al. Reference Hickel, Kallis and Jackson2022; Kotzé & Adelman Reference Adelman, French and Kotzé2021).

A further concern is that the development of newer technologies and the tightening of standards in developed countries have resulted in inefficient equipment, containing ODSs due to be phased down or phased out, being offloaded in developing countries, which will bear the associated environmental, economic, and social costs. Developing countries have accordingly called for policies and measures to prevent such dumping (Agyarko et al. Reference Agyarko, Andersen and Ferris2021; UNEP 2022).

Furthermore, the ozone regime is grounded in science, and the Montreal Protocol has been referred to as an example of ‘the power of Earth systems science in facilitating international environmental lawmaking’ (Boyd Reference Boyd2017: 486). The ozone regime provides that measures to protect the ozone layer should be based on scientific knowledge, and there are references throughout the Vienna Convention and Montreal Protocol to scientific and technical information. Interestingly, around the time that the Vienna Convention and Montreal Protocol were concluded, economic growth came to be linked to scientific and technological progress; and Allan argues that the ‘tight link between growth and scientific and technological progress continues to be reproduced in the present international order’ (Allan Reference Allan2018: 261). In practice, knowledge is developed by several scientific and technical assessment panels, which are largely dominated by men from northern countries (see, e.g., UNEP n.d.).

Although the problem of stratospheric ozone depletion was caused by human-created substances, ozone depletion and other problems arising due to the implementation of the ozone regime have implications for all life on earth. The absence of references in the ozone regime to natural ecosystems (apart from references to ‘human health and the environment’) and non-state actors – in contrast to other IEL agreements – is striking.

The following section begins to explore how some of these concerns might be addressed.

3.4 The Evolution of Values under the Ozone Regime

While some of the aforementioned concerns might be addressed through the tightening of definitions and narrowing of exclusions (see Du Toit Reference Du Toit, Kulovesi, Yamineva and Recio2023), the focus here is on deeper shifts that might be required. At a broader level, there have been calls for the transformation of ‘modern society’s anthropocentric and colonial worldview through which nature exists to serve humankind’ (Piccolo et al. Reference Piccolo, Taylor and Washington2022: 1). In the context of international law, it has been argued that reforms of international laws and institutions are required in order to ‘make them less anthropocentric and more responsive to the imperatives of the global ecological crisis’ (Lawrence Reference Lawrence2022: 577). However, there is no consensus on how this could be achieved.

A growing trend, prominent at the national level, is the granting of rights to nature generally or to specific natural entities, such as rivers (see, amongst others, Boyd Reference Boyd2017; Kotzé & Villavicencio Calzadilla Reference Kotzé and Villavicencio Calzadilla2017; Villavicencio Calzadilla & Kotzé Reference Villavicencio Calzadilla and Kotzé2018; Tănăsescu Reference Tănăsescu2020). While the recognition of rights for nature might present a response to concerns around anthropocentrism in environmental law, several problems have been highlighted. For example, granting rights to nature may further entrench divisions between human and non-human earth system components (Biber Reference Biber2022; O’Donnell Reference O’Donnell2022). Furthermore, Tănăsescu challenges the assumption that rights of nature are ecocentric or of Indigenous origin and argues that extending personhood to natural entities ‘reproduces the centrality of the human’ (Tănăsescu Reference Tănăsescu2020: 448), which clearly does not address concerns regarding the anthropocentrism of IEL. Spitz and Penalver (Reference Spitz and Penalver2021: 81) also question whether granting personhood to natural entities actually makes a difference in terms of legal outcomes; and Kurki (Reference Kurki2022) goes further, arguing that granting personhood to natural entities is simply a legal fiction (even though it may have symbolic value). While not possible to explore fully here, the value of granting procedural rights to natural entities has also been highlighted (Schapper et al. Reference Schapper, Hoffmann and Lee2022; see also Tănăsescu Reference Tănăsescu2020; Winter Reference Winter2021).

It has also been proposed that ecological integrity or ‘the integrity of Earth’s life-support systems’ should be established as a grundnorm of international law, ‘similar to the grundnorm character that human rights or the rule of law have in domestic and international law’ (Kim & Bosselmann Reference Kim and Bosselmann2015: 194). Adelman argues further that ‘ecological integrity should be both a precondition and the ultimate objective of [international environmental law] in order to stay within the safe operating space of the planetary boundaries’ (Adelman Reference Adelman, French and Kotzé2021: 77). Some IEL agreements have recently started to recognize the importance of ecological integrity. For example, the Paris Agreement (UNFCCC 2015: Preamble) emphasizes ‘the importance of ensuring the integrity of all ecosystems, including oceans, and the protection of biodiversity, recognized by some cultures as Mother Earth’. The Glasgow Climate Pact contains similar language, and it notes ‘the importance of ensuring the integrity of all ecosystems, including in forests, the ocean and the cryosphere, and the protection of biodiversity, recognized by some cultures as Mother Earth’. While not binding, the 1982 World Charter for Nature (UNGA 1982) arguably goes even further through its acknowledgement of the intrinsic value of nature in the following terms: ‘[hu]mankind is a part of nature and life depends on the uninterrupted functioning of natural systems’, and ‘[e]very form of life is unique, warranting respect regardless of its worth to [humans]’. Attention could be paid to including similar language within the preambular text of the ozone regime.

In regard to concerns around the predominant reliance on (Western) scientific knowledge, Garver (Reference Garver2019: 167) argues that achieving a ‘mutually enhancing human-Earth relationship’ requires that human choices are informed by contemporary science as well as ‘traditional ecological knowledge of people with long-standing connections to place, including an understanding of the behavior of complex adaptive systems’. More recently, some IEL treaties have started to refer to non-Western knowledge. For example, under the climate change regime, the Paris Agreement (UNFCCC 2015: article 7(5)) acknowledges that ‘adaptation action should follow a country-driven, gender-responsive, participatory and fully transparent approach, taking into consideration vulnerable groups, communities and ecosystems, and should be based on and guided by the best available science and, as appropriate, traditional knowledge, knowledge of indigenous peoples and local knowledge systems’. Similarly, the Glasgow Climate Pact (UNFCCC 2021: article 93) emphasizes ‘the important role of indigenous peoples’ and local communities’ culture and knowledge in effective action on climate change and urges Parties to actively involve indigenous peoples and local communities in designing and implementing climate action’. It would also be possible to include this type of language within the preambular provisions of the ozone agreements.

More broadly, it will be necessary to move beyond ‘mainstream forms of development’ (Adelman Reference Adelman, French and Kotzé2021: 68) and the current ‘growth-insistent paradigm’ (Garver Reference Garver2019). Proposals include embracing non-Western perspectives such as sumac kawsay or buen vivir (Acosta Reference Acosta2017) and implementing degrowth strategies (Hickel et al. Reference Hickel, Kallis and Jackson2022). Buen vivir translates directly as ‘living well’; although it is said to translate more accurately as ‘harmonious coexistence’ (Calisto Friant & Langmore Reference Calisto Friant and Langmore2015: 1). For its part, the degrowth concept originated in ecological economics, and it is described as ‘a planned reduction of energy and resource use designed to bring the economy back into balance with the living world in a way that reduces inequality and improves human well-being’ (Hickel Reference Hickel2021: 1105). Embracing such perspectives is viewed as important to efforts to shift away from the anthropocentric basis of law and governance and to tackle the socio-ecological challenges of the Anthropocene (see, e.g., Calisto Friant and Langmore Reference Calisto Friant and Langmore2015; Kotzé & Adelman Reference Kotzé and Adelman2023). However, their realization would go beyond the scope of the ozone regime, and indeed IEL, and would require wide-ranging societal and political transformations.

In the interim, measures like those described earlier, such as the recognition of ecological integrity and non-Western perspectives within the ozone regime, could represent starting steps in shifting away from anthropocentric and utilitarian values, and they could also bring the ozone regime in line with more recently concluded IEL agreements.

3.5 Concluding Remarks

The ozone regime is widely considered to be one of the most effective international law regimes to date. While it has been very successful in regard to phasing out the substances under its control and in ensuring that we remain within the planetary boundary on stratospheric ozone depletion, the earlier discussion has highlighted several concerns. Apart from several technical gaps, it has been argued that the ozone regime (similarly to IEL in general) is based on a utilitarian and human-centred approach and implicitly supports ongoing ‘sustainable’ development, which has given rise to various socio-ecological harms. Furthermore, although it has been argued that the ozone regime gives effect to the principle of common but differentiated responsibilities, as discussed earlier, power imbalances between developed and developing countries remain, which enable the exacerbation of injustices. While not presenting definitive answers, this chapter has attempted to explore the evolution of values underlying the ozone regime so that it may continue to effectively protect stratospheric ozone, while also contributing to efforts to equitably protect all earth system components.

4.1 Introduction: Why Should You Care?

A blanket of ozone, an unstable bond of three promiscuous oxygen atoms, cossets the globe from harmful UV radiation. Without it ‘life on Earth would not be possible’ (Mohr Reference Mohr2021: 31). At ground level, however, this same bond of oxygen atoms is hazardous – interfering with the flourishing of human and plant life caught in its presence. Industrial-age human activity has done two things: destroyed beneficial stratospheric ozone and created destructive atmospheric ozone. The activities of some humans, therefore, interfere with the well-being of themselves, other human beings, animal and plant life. Furthermore, they interfere with the oxygen bonds that make ozone itself and ozone’s natural relationships. The focus of this chapter is on stratospheric ozone, and it is, I think, important to have noted the contradictory impacts of ozone at stratospheric and atmospheric levels on human and other planetary life forms. It is also important to note that the natural balance of ozone at both levels is disrupted by the activities of those industrial/Western/modern human beings who pay scant heed to any form of responsibility to maintain harmonious relationships with the non-human realm.

It is this lack of a sense of responsibility to the natural realm that the idea of the planetary boundaries seeks to address – not in an ethical frame but a scientific one. Put simply, while the ozone layer high in the stratosphere supports ‘life on earth’ in its multiple meanings, a particular anthropocentric ‘life on earth’ has reciprocated not in a relationship of care and nurture, but one that seeks to define acceptable limits to ozone’s destruction. That is, as with all the planetary boundaries articulated in Rockström et al.’s seminal works (Reference Rockström, Steffen and Noone2009; Steffen et al. Reference Steffen, Richardson and Rockström2015), the idea of an ozone boundary rests on (at least) two assumptions. First, the natural systems that support human well-being can be ‘extracted’ from for the accumulation of human property and/or wealth. By ‘extracted’ I mean may be interfered with by human activity in a way that reduces their natural extent and/or functions. Second, natural systems can be viewed as bounded, that is as non-relational.Footnote ¹ In what follows I will argue that, while undoubtedly an agent of good, the idea of planetary boundaries rests nested in an anthropocentric, colonial ontology that silently undergirds the epistemic community (Haas Reference Haas1991)Footnote ² of Western science, a community that deliberately expunges (or claims to expunge) values from its reckonings. Furthermore, the scientific endeavour of planetary boundaries is wrought from that same ontological furnace. The question then is, can you resolve a problem from within the same ontological foundations whence it arose?

My goal here is to try to (un)think planetary boundaries and (re)think planetary relationships. My intuition is that to describe a set of boundaries up to which ‘we’Footnote ³ may pollute, assumes the same basket of rights that is leading the planet and all that draws sustenance from it to a precipice. The assumptions underpinning the concept of planetary boundaries are another example of a colonial relationship, or to paraphrase Max Liboiron (Reference Liboiron2021), planetary boundaries are colonialism. That is, they have imbedded an ethics that legitimizes the enclosure of a commons (in this case stratospheric ozone) for the benefit of a privileged few, who are often, but not exclusively, the heirs of historical colonial appropriation of others’ Land-basedFootnote ⁴ territory – the wealthy Western states and their citizens (although not all citizens equally). My claim is ozone destruction and the ozone boundary might be framed as a property right founded in an ethics that legitimates the way that some human behaviour messes with the natural relations within the air, within the atmosphere and stratosphere. This chapter is less about how much we can pollute to be safe (the Montreal Protocol has successfully eliminated the main culprits (Weber et al. Reference Weber, Arosio and Coldewey-Egbers2022)), but, rather, it is a challenge to that framing – a framing that suggests (some) humans have a legitimate right to interfere in atmospheric and stratospheric relationships to the point/level that is just below one that is harmful to humans. My claim is that rather than a simple duty to protect humans, there needs to be a reconfiguration of the conception of duties and responsibility to support the well-being of ozone and ozone’s (and all other planetary boundaries’) basket of relationships – with humans and other planetary beings, the air, elements, and stratosphere.

An anticolonial approach challenges the root assumption that humans can legitimately ‘extract’ oxygen atoms from ozone up to a certain level. I suggest that chemical pollution does harm to the natural relationships that exist within the blanket of ozone that cossets the earth – it is an extractive relationship that generates negative externalities: burnt skin or scorched crops say. Secondly, I use the idea of extraction to indicate that the governance frameworks and the planetary boundaries literature represent ozone as independent from its relationships (and from any human obligations and duties to ozone itself) and that this representation is a function of governance regimes and epistemic and ontological formations – ones that isolate elements one from the other and create an illusion of boundaries. These are the same epistemic and ontological foundations from which the need for a scholarship on planetary boundaries arose. Equally I challenge the legitimacy of creating ozone at terrestrial levels and thus burdening human, plant, and animal life with reduced welfare and intervening in natural atmospheric chemical relationships and elemental processes and relationships. However, and to reiterate, here the focus is on stratospheric ozone the subject/object of the planetary boundary.

This chapter takes the following form. I assume you have read the introduction to this section and are familiar with the basics of the ‘ozone hole’ and the Montreal Protocol. However, the chapter stands alone without that background. I briefly outline the ozone success story, that is that the ozone hole is the only planetary boundary that has been rescued from a tipping point.Footnote ⁵ I will then introduce the idea of ozone as relationship, followed by a more comprehensive discussion of planetary boundaries as colonialism. I conclude by proposing an anti colonial alternative in which I posit that humans have a responsibility to enhance ozone’s natural relationships and demonstrate that in so doing the need for (imaginary) planetary boundaries collapses.

4.2 Ozone as Success Story

Limiting depletion of stratospheric ozone is rightfully lauded as a global success story: one of exemplary scientific and political cooperation. There were tailwinds, of course, that facilitated this success: scientists willing to implement the precautionary principle quickly;Footnote ⁶ politicians prepared to respect scientific advice; the euphoria of ‘the end of history’Footnote ⁷ as the Cold War ceased and international cooperation heralded a new future; a small number of producers of the key chemicals (chlorofluorocarbons or CFCs) responsible for stratospheric ozone’s depletion; and suitable, cost-effective replacement chemicals readily at hand. Scientists identified a problem that industrial science could resolve under the right regulatory conditions, and politicians acted quickly to enact that regulation.

First, the Vienna Convention of 1985 and then the Montreal Protocol, 1987, provided the right regulatory conditions. From the time at which it was realised that man-made/manipulated chemicals, those produced in industrial and agricultural processes and used in consumer-ware, were destabilizing the fragile bonds of ozone’s oxygen atoms to the implementation of the Montreal Protocol was rapid. The chemistry and risk were illuminated, for instance, by Crutzen (Reference Crutzen1971, Reference Crutzen1972, Reference Crutzen1974), and repeatedly thereafter. Pressure for action was mounting on and in political circles when in 1985 Farman et al. (Reference Farman, Gardiner and Shanklin1985) provided irrefutable evidence of a hole in the ozone layer over Antarctica. The Montreal Protocol was adopted swiftly thereafter.Footnote ⁸ So successful has been the regulatory regime that the UNEP Ozone Secretariate wrote in 2019:

And yet in April 2020 Nature reported a hole in the ozone layer above the Arctic (Witze Reference Witze2020), a big hole the headline said, possibly the biggest ever recorded. The cause? Unusually cold temperatures. However, temperature was not the direct cause: the blame must still be placed on anthropogenically produced and emitted pollutants. The cold allowed high-altitude clouds to form and the pollutants reacted with the clouds to destabilize ozone’s fragile bonds or, as the article claims, to ‘chew away at ozone’ (Witze Reference Witze2020: 19). In 2021 NOAA announced the ozone hole above the Antarctic was enlarged – in the top 25 per cent recorded (National Oceanic and Atmospheric Administration 2021). The culprit they were quick to note was not chemical alone but rather again a matter of colder than usual Antarctic temperatures. The suggestion is that the Protocol may be said to remain a success story. However, simultaneously the ozone layer remains vulnerable. These stories highlight two features relevant to my argument: (1) the Montreal Protocol limited emissions of ozone ‘chewing’ chemicals but did not eliminate them from either production or release; and (2) ozone exists as a set of spatial, temporal, elemental, and chemical relationships, not as an individuated chemical bond.

Let’s circle back to the previous quote from the Ozone Secretariat (is it quaint to think a chemical blanket 15 kilometres above the earth’s surface should have its own secretariat? Perhaps not). They say the agreements ‘control production and consumption of … ozone depleting … substances’. Despite the science of harm, the ethics underscoring the agreements rests in an assumption that some production and consumption of these chemicals may and will continue. That is, there is agreement that some human beings are entitled to consume a portion of the global commons that is stratospheric ozone. I suggest it is possible to draw a direct line from three historical moments which continue to foist great weight on some – some people, some environments, some elements – and the ethics of the Montreal Protocol and the logic of planetary boundaries: the enclosures of common lands in Europe; the appropriation of lands from the indigenous First Peoples in the colonies and their transfer to private title; and Locke’s rationale for legitimating such enclosures (Laslett & Locke Reference Laslett and Locke1997: § 5). That enclosure was/is legalized does not make it just. At each juncture what was previously held in common for the good of all was re-labelled ‘property’ and assigned to the benefit of the owner.

I approach the ozone boundary as an object of colonization because it seems to embed a property right to pollute the global commons, an assumed right to ‘eat into’ or ‘extract from’ the atmosphere and stratosphere. Here I attempt to weave an anti colonial approach to human responsibilities to ozone.

4.3 Ozone’s Relationships

The planetary boundaries literature describes a ‘safe operating space for humanity’ (Steffen et al. Reference Steffen, Richardson and Rockström2015), and the Montreal Protocol is held as the case study for successfully navigating one boundary’s limits. I trouble this notion by focusing on the relational entanglements of the planetary system – human, animal, vegetable, mineral, and elemental. I am suggesting that ozone cannot, and should not, be seen as separate from its own relationships – its own kinships as Anja Kanngieser and Zoe Todd might have it (Kanngieser & Todd Reference Kanngieser and Todd2020). I am steering you towards understanding ozone not as individual molecules, nor as a cossetting blanket, but rather as a set of relationships. Furthermore, I am also suggesting ozone’s protection is ethically something more than the safety of humanity. All life on the planet depends to some extent on stratospheric ozone. Ozone exists as a set of spatial, temporal, elemental, and chemical relationships, not simply as an individuated chemical bond, a molecule. The very existence of the ‘ozone layer’ suggests a relational coming-togetherness predilection in ozone. The layer is not ‘just a layer’ but a(n) (o)zone of relationship. It exists despite humanity and humanity exists because of ozone. It has liveliness of its own that is worthy of respect: it is not simply a passive victim of human misadventure.

Ozone is not a ‘case-study’ (Kanngieser & Todd Reference Kanngieser and Todd2020). Oxygen is a promiscuous element – in and out of relationships constantly. This, admittedly, is an observation from someone who is neither a chemist nor a physicist. Nevertheless, this seems an appropriate description for an element that readily detaches from one chemical bond to form another. ‘Stratospheric ozone is formed and consumed naturally by photochemical reactions’; its oxygen atoms move in and out of relationships such that ‘[a]t any time, the formation and consumption of ozone proceed simultaneously’ (Freedman Reference Freedman, Nemeh and Longe2021: 3272). It is this promiscuity that might be said to have led to the ozone hole. The love triangle of three oxygen atoms that form ozone quickly collapses once chlorine, fluorine, or nitrogen, and other pollutants, join the party. It is the relational instability between the three oxygen atoms of an ozone molecule that the Montreal Protocol acknowledges and that the concept of planetary boundaries wishes to (re)stabilize by limiting the number of disruptive chemicals in the stratospheric commons.

But what of ozone’s origin stories – these too are relational. The earth’s oxygen, the precious life-giving oxygen of the atmosphere, originated in a relationship between cyanobacteria – blue-green algae – sunshine, water, and carbon dioxide. A planet without these tiny organisms, energy from the sun, and the carbon, hydrogen, and oxygen caught in bonds of water and carbon dioxide is a planet without oxygen. Atmospheric oxygen originates from a critical relationship between plant life and the sun, and yet the concept of the ozone planetary boundary does not directly protect the critical ‘feed stock’Footnote ⁹ life-form required for ozone – oxygen. The boundary focuses on the direct destruction of ozone in stratosphere.

Burning plant life, or more accurately the death and destruction of large ecosystems, is attributed to the destruction of stratospheric ozone in 2020–21. Directly linked to the wildfires that razed one-third of Australia’s natural forests, the ozone layer shrank in those years. Particulate matter, dead trees, dead animals, and dead insects not only insinuated their way into the lungs of Australia’s human and surviving non-human animals but rode an atmospheric elevator into the stratosphere. The figures of death and destruction from those Black Summer fires are now legend. What is less heralded is their effect on the ozone layer. ‘1 million tons of smoke particles [were slung] into the atmosphere, reaching up to 35 kilometres above Earth’s surface’ (Chu Reference Chu2022: n.p.). These catastrophic fires and others, incinerating forests around the globe in what seems like an endless seasonal global procession, insert their presence into the stratosphere and play cuckold to the ozone bonds. Such fires enter a relationship with ozone, albeit a destructive relationship. Researchers ‘estimate that [a] smoke-induced chemistry depleted the column of ozone by 1 percent’ which exactly cancels out ozone’s gains over the past 10 years (Chu Reference Chu2022: n.p.). The Ozone Secretariat’s expectation that the ozone layer will be fully repaired by the ‘middle of this century’ now seems hopeful at best, naïve at worst because it addresses only one of the colonizing relationships of modernity; that of industrial chemicals. Land use, land abuse, the tumults of climate change triggered by colonial extractivismFootnote ¹⁰ are also members of the ozone attack-gang.

Forest (wild) fires, though, are related to other ‘modern’ practices and are intimately entangled with the other great atmospheric threat, climate change. In Australia (and the west coast of North America) these forest fires sear a straight line of culpability to colonial violence, land theft, land-use practices, and Indigenous repression. The philosophies of modernity severed practices of relating and stewardship and embedded those of dualismFootnote ¹¹ and extraction. The idea of property rights enclosed Land and created land from which Indigenous people (and their philosophies of entanglement with and care of Land (Celermajer et al. Reference Celermajer, Schlosberg and Rickards2021; Kimmerer Reference Kimmerer2013; Stewart-Harawira Reference Stewart-Harawira2005; Whyte Reference Whyte, Heise, Christensen and Niemann2017; Winter Reference Winter2022)), native animals, and plant life are excluded and replaced by extractivist farming,Footnote ¹² forestry, and mining. The Lockean philosophy that underscored land-based enclosure now underpins the idea of planetary boundaries – the right to ‘enclose’ the atmosphere (and land, waterways, etc.) up to a ‘safe operating limit’ to facilitate progress, productivity, and GNP. Chemicals production continues, climate is changing, forests are ablaze, and the ozone layer at least doubly damned. Damned first by CFCs and now, on the cusp of restoration, damned by the entangled relationships between intensive agricultural extractivism, colonialism, climate change (and thus also fossil fuel mining/extraction), and wildfires.

Furthermore, the relationship between oxygen atoms forming an ozone molecule depends on prior elemental relationships. Ozone’s origin story begins with cyanobacteria – blue-green algae which converts sunshine, water, and carbon dioxide, and produces oxygen. And beyond energy from the sun, ozone has another elemental relationship – with lightening and light. Lightening is known to create ozone – at both stratospheric and atmospheric levels – and ozone is produced also ‘from the photoexcitation of the (O₂)₂ species’ (Braslavsky & Rubin Reference Braslavsky and Rubin2011: 1517). Its creation, in other words, relies on a complex web of relationships between living and non-living matter, elements and natural phenomena, sun and earth. Conversely, its destruction ‘is the collateral damage of industrial society’ (Haas Reference Haas1991: 225).

4.4 Ozone’s Planetary Boundary Is Colonialism

The description ‘planetary boundaries’ camouflages ongoing colonial practices of privatizing the commons: hidden within the fabric of the descriptor is an assumption that humans – some humans – have a right to pollute (up to some predetermined limit), a right to ‘colonize’ the stratosphere, to ‘enclose’ it. This does two things: it means only some humans get to access the limited availability to enclose (and I will expand on this concept fully next, please bear with me for now); and it makes ozone’s relationship to thriving – for human, animal, and plant life – tenuous, precarious even, for others. The underlying assumption is some degree of environmental harm is tolerable if it enhances GDP and some human lives, even when it involves appropriation of a global commons.

Human-induced ozone depletion, which grows from a system that assumes nature is the ‘sink’ for human waste and waste products (Liboiron Reference Liboiron2021), is a form of extractivism. Like the profligate use of fossil fuels, so the convenience of CFC propellants to eject hairsprays and whipped cream ‘extract’ oxygen atoms from ozone to created new bonds with chlorine and fluorine and carbon from the CFCs reaching the stratosphere. Likewise, the release of CFCs when refrigeration and air-conditioning units are dumped – as a product of planned obsolescence – ozone becomes the victim of corporate profits. The fragile bonds of three promiscuous oxygen atoms are easily shattered to soak up the unnatural by-product of human convenience, luxury, corporate bottom lines, and waste (Winter & Schlosberg Reference Winter and Schlosberg2024). Ozone’s very being is then extracted from the stratosphere, its existence terminated. It is apparent, then, that in these processes we find there are no boundaries – everything, everyone, every inter- and intra-action (Barad Reference Barad2012) is connected.

The stratosphere, that which might once have been imagined an infinite sink, a convenient ‘away’ for industrial externalities,Footnote ¹³ a repository so infinite that it need not be accounted for (in the multiple meanings of account), is now recognized (by some) to be otherwise, to be fragile and perilously finite. Scientists’ realization that the ozone hole existed as a result of human activity is a vivid reminder there is no ‘away’. Making this realization palpable has been one success of the planetary boundaries project. It has been a success too of the Montreal Protocol. However, presenting each domain of planetary overreach as bounded – as discrete and contained – means the relational is subsumed by the bordered. Subsumed too are the world’s extant knowledge traditions that base their epistemologies within relationality.

4.5 An Anticolonial Planetary Boundary for Ozone

The message of this chapter is: boundaries are an illusion. The ‘boundary’ between you and me is broken the moment we share air mingled with our breath or as microbes jumped ship from me to you as we shook hands (Yong Reference Yong2016). Even if there is not physical contact between us, our brains can be forever changed as we share ideas, knowledge, emotions, and theory, and our synapsis lay them down as memory. That is, as Barad suggests earlier, being on earth means being alive to the world in its wholeness. The idea of boundaries creates an illusion of separation where there is interaction, blending, sharing, blurring. The river that flows between states or countries contains and shares shards from each bank, blends them, redeposits them regardless of the designated boundary. The atmosphere is intimately entangled with plant life, humanity’s offal and pollutants, with lightening, wildfires, volcanoes, winds, water, minute particulate matter, and gobbling chemicals. There are no boundaries to some of humanity’s arrogance: it touches everything, and, in Karen Barad’s words, ‘[t]ouch is never pure or innocent’ (Barad Reference Barad2012: 215).

One great good the Montreal Protocol and the literature on the planetary boundaries have wrought is redirecting attention from the divisiveness of the ‘global’, the discourse of borders, nationstates, competition, and multi-nationalism. As Dipesh Chakrabarty so convincingly argues, a global mindset is incapable of resolving the planetary crisis of climate change – that is, a global focus, born from the same the epistemological and ontological foundations as colonialism, bakes in anthropocentrism and competition (Chakrabarty Reference Chakrabarty2021). Without detracting from the good of the planetary boundaries project, my argument here is similar to Chakrabarty’s, that the threats to planetary thriving cannot be resolved solely from within the philosophy from which they arose. Importantly a decolonial planetary vision faces towards multi-species multi-elemental flourishing in their/its own right.

I am suggesting an anticolonial planetary (non)boundary for ozone requires a relational ethic in which duties and responsibilities are to the relationships that inhere to ozone. That, as Max Liboiron says, any level of pollution breaks the bonds of relationality and thus the responsibility between human and the planetary system: it is colonial. The subject of planetary justice is not simply humanity, not simply the sensate or living being, it extends to all matter. Anticolonial planetary boundary scholarship and policymaking require development of and engagement with relational epistemologies and ontologies. Anticolonial planetary studies decentre the human and Western thinking patterns, epistemologies, and ontologies, and include all living beings, the elemental, and geophysical. In an anticolonial boundary-less planetary vision there are no polluting property rights. An anticolonial planetary justice proposes a planet on which a life-sustaining planetary net of overlapping (local) relationships are the subjects of justice.