22.1 Introduction
This chapter addresses ocean acidification (OA) from an environmental ethics perspective. Ocean acidification is seen as a paradigm case for post-normal science. At its core, the chapter adopts and substantiates several ethical building blocks from a discourse-pragmatic approach, as (a) common heritage of humankind, (b) strong sustainability, (c) Aldo Leopold’s principle, and (d) ecosystem services, with a special eye on cultural services. The idea to attribute inherent moral value to marine organisms and ecological systems is seen critically.
This chapter emerged from the research programme BIOACID (Biological Impacts of Ocean Acidification) being conducted at Kiel University. Within the final period of the BIOACID research programme, a work package on environmental ethics was included to address the underlying normative issues. This project resulted in a monograph: Frederike Böhm and Konrad Ott, Impacts of Ocean Acidification: An Analysis from an Environmental Ethics Perspective (Böhm & Ott, Reference Böhm and Ott2019).Footnote 1 The following chapter presents the essential lines of reasoning of this book and adds new thoughts. It is organized as follows: Section 22.2 gives a brief overview of the scientific dimension. Section 22.3 presents a post-normal-science framing of OA. Section 22.4 deals with interrelated sources of normativity which stem from environmental ethics. Section 22.5 addresses the problem of defining a planetary boundary for OA.
22.2 The Scientific Basis
Ocean Acidification refers to a reduction in the pH of the ocean over an extended period, typically decades or longer, which is caused primarily by uptake of carbon dioxide (CO2) from the atmosphere, but can also be caused by other chemical additions or subtractions from the ocean. Anthropogenic ocean acidification refers to the component of pH reduction that is caused by human activity.
Ocean acidification is one of several global stressors to the future ocean. It occurs alongside ocean warming and climate change, a complex of problems mainly resulting from continued carbon dioxide emissions. Closely related are issues of deoxygenation and eutrophication. In a marine ecosystem context, it is impossible to isolate the impacts of OA from those of co-occurring and interacting environmental pressures. Many studies and risk assessments therefore consider combined and synergistic effects (Hales et al. Reference Hales, Chan and Boehm2015). Thus, one has to distinguish OA and its impacts (a) in isolation and (b) in context with other pressures. A focus on (a) may underrate the problem.
OA, as climate change, is an unintended side effect of CO2 emissions. The basic chemistry is well known, CO2 entering the ocean changes seawater chemistry via several chemical reactions. The main net effects are an increase of H+ ions and consequently a decrease in pH and an increase in bicarbonate (HCO3) ions along with a decrease in carbonate saturation. In the last two centuries, global average surface seawater pH has decreased by about 0.1 units (pH 8.21 to pH 8.1) (Rhein et al. Reference Rhein, Rintoul and Aoki2013). This is equivalent to approximately 26 per cent increase in hydrogen ion concentration. An overall reduction of oceanic pH by 0.4 pH units (pH 8.21 to pH 7.8) seems possible in the worst case (IPCC 2014; Secretariat of the Convention on Biological Diversity 2014). Under the most optimistic IPCC scenario (‘RCP 2.6’), ocean acidification is still projected to increase globally until the end of the twenty-first century and may slowly recover after the mid twenty-second century (IPCC 2014).
OA is occurring extremely fast on geological time scales and irreversible on a historical scale (Knoll & Fischer Reference Knoll, Fischer, Gattuso and Hansson2011). Natural restoration of ocean chemistry to a state similar to pre-industrial levels would take tens of thousands of years (The Royal Society 2005). From a human perspective, OA is a creeping and long-term process with a time lag between cause and effect. While the process has already started, the full effect will occur in the future. While CO2 emissions represent the main driver of OA, there are also local factors which may cause or intensify it. Coastal drivers of OA can be pollutants, erosion of soils, sulphur dioxide precipitation, hypoxia, eutrophication as well as changes in circulation patterns, or biological processes as metabolism rates (Duarte et al. Reference Duarte, Hendriks and Moore2013). Thus, scales, context, and local variations matter.
At the species level, OA can affect physiological functions like formation of shells and skeletons by calcifying species, internal pH regulation, or photosynthesis. Besides such direct effects on organisms, many are also indirect (for example via food web or habitat change). OA lowers tolerance to ocean warming by coral and crustacean species, thereby enhancing the effect of OA. With high likeliness, calcifying organisms will be the most negatively impacted group of species (Kroeker et al. Reference Kroeker, Kordas and Crim2013).
Therefore, some authors suggest establishing thresholds for OA based on the aragonite saturation state of seawater (Rockström et al. Reference Rockström, Steffen and Noone2009). This proposal would define an additional ‘planetary boundary’. Such a planetary boundary is not a natural one but relies on normative presuppositions. Global thresholds can serve well for political purposes. If it has been prudent to determine such threshold in climate policy, it might be prudent to argue for an analogous threshold in the case of OA (Section 22.5). Without ethical grounding, any fixation of an OA threshold in terms of average pH, however, looks arbitrary because it can’t be derived from scientific data alone (Section 22.4).
22.3 The Framing: Wicked Problems and Post-Normal Science
From an epistemological perspective, OA can be conceived as a case of post-normal science. ‘Post-normal science’ is a term that refers to wicked real-world problems in which stakes are high, uncertainties large, values in dispute, and decisions hard and urgent (Funtowicz & Ravetz Reference Funtowicz, Ravetz and von Schomberg1993, Reference Funtowicz, Ravetz, Westra and Lemons1995). OA has characteristics of a wicked problem, ‘where time is running out, where decision makers lack agency, where incentives are in place that push us into a short-termist downward spiral, and where all actors in the system are ourselves part of the problem’ (Thomas Reference Thomas2014). The term ‘wicked’ refers to critical features that overburden the usual ‘modern’ ways of problem solving via law, incentives, pricing, policymaking, and technological fixes. Those features are marked in this section.
From a scientific perspective, assessing OA must distinguish between OA alone (‘as such’) and OA in the context of multiple ocean pressures, as ocean warming, pollution, overfishing, and so on. Even seen in isolation, uncertainties remain high. Contextualizing increases uncertainties about long-term interactions, non-linear effects, cascades of effects, positive and negative feedbacks, and so on (Section 22.2). Riebesell and Gattuso (Reference Riebesell and Gattuso2015) emphasize knowledge gaps in ecosystem level responses, the potential of long-term adaptation, and effects of multiple drivers in context. OA exceeds natural variability of seawater alkalinity and carbonate saturation; that is, the human driver is one that the marine ecosystems are not pre-adapted to. This makes predictions uncertain. OA and ocean warming may have cascading effects on marine life and ecological processes (Secretariat of the Convention on Biological Diversity 2014).
From a policy perspective, however, OA has been addressed by Sustainable Development Goal 14 (SDG 14) ‘Life below water’. Sustainable Development Goal 14 aims to ‘conserve and sustainably use the oceans, seas and marine resources’. Sub-target 14.3 specifically addresses OA in the aim to ‘Minimize and address the impacts of ocean acidification, including through enhanced scientific cooperation at all levels’ (United Nations Department of Economic and Social Affairs 2022). Sustainable Development Goal 14 and its sub-target 3 serve as a reference point in international governance for the objective of combatting OA. The wording of sub-target 14.3 refers to the impacts of OA, not to OA as such. To determine a threshold (Section 22.5) might suppose a different understanding of sub-target 14.3: ‘Minimize OA and address and minimize its impacts’.
From a temporal perspective, OA is an intergenerational problem. Whereas in climate change, the members of the human species feel many of the impacts more directly, for example through extreme weather events, heat waves, droughts, and sea level rise, OA foremost affects natural systems. Humans remain largely unaffected by OA. From an anthropological perspective, OA is a creeping and invisible problem that does not represent a direct hazard to human life and health. Since humans have evolved in terrestrial environments with specific threats, they are not ‘wired’ to perceive long-term risks within marine systems. From the moral point of view, however, OA does not appeal to our common moral sentiments, convictions, and imagination. OA doesn’t victimize individual persons, and it does not fall within the scope of problems that most people in general regard as moral ones. Thus, OA touches limits of moral perception and modes of moral attentiveness. OA falls outside the scope of usual moral problems. It is ‘wicked’ and ‘post-normal’ for ethics as well.
22.4 Environmental Ethics
22.4.1 Environmental Pragmatism
Ocean acidification falls into the field of environmental ethics. Environmental ethics is a discipline of applied practical philosophy, which investigates the moral and value-laden relationships of human beings (individuals and collectives) to natural environments (for overview see Krebs Reference Krebs1999 and Attfield Reference Attfield2014). Environmental ethics has mostly focussed on terrestrial and limnological systems. It has not been applied to the ocean very often (laudable exceptions are Norton Reference Norton and Dallmeyer2003; Wolf Reference Wolf and Dallmeyer2003). Dallmeyer (Reference Dallmeyer and Dallmeyer2003: p. 278) postulates a ‘second great awakening – this time for the ocean’. Roberts (Reference Roberts2013) also points in this direction. In recent years, there have been many pleas for ocean literacy, ocean stewardship, ocean sustainability, ocean recovery, ocean ethics, and ocean health (Auster et al. Reference Auster, Fujita and Kellert2009; Mengerink et al. Reference Mengerink, van Dover and Ardron2014; Visbeck et al. Reference Visbeck, Kronfeld-Goharani and Neumann2014; Blaustein Reference Blaustein2016; Franke et al. Reference Franke, Blenckner and Duarte2020).
My approach to environmental ethics is close to environmental pragmatism, which studies human–nature interactions and practices and wishes to modify them towards more sustainable and preservationist modes (‘wise use’) (Norton Reference Norton2005, Reference Norton2015). I also wish, however, to reconcile discourse ethics and environmental ethics (Hendlin & Ott Reference Hendlin and Ott2016). This discourse-pragmatic approach can select specific lines of reasoning out of the entire universe of environmental ethical discourse if such lines look appropriate for specific challenges and problems, as OA. Not all arguments fit all problems equally well. Humans may have different reasons to protect endangered species or wilderness areas, to choose a vegetarian diet, to perform organic gardening or to distribute scarce environmental resources fairly among humans. This section rests on hopes that appropriate reasons have been selected which fit the case of OA.
One may ask why one should bother morally about OA. Here comes an answer: If a moral person has been informed about OA (Section 22.2), she should have appropriate emotions and attitudes about it. OA and ocean warming imply the insight that not even the ocean remains unaffected and safe from anthropogenic climate change. Being terrestrial beings, ‘we’ humans must recognize that ‘we’ are responsible for the long-term fate of the ‘great otherness’ on planet Earth: the ocean. In ‘The Sea Around Us’, Rachel Carson wrote about ‘man’: ‘He cannot control or change the ocean as, in his brief tenancy of earth, he has subdued and plundered the continents’ (Reference Carson1951: 20). Retrospectively, this echoes a final illusion of planetary infinity und human limitations. Meanwhile, Carson has been proven wrong by the great and excessive acceleration since the 1950s. Yes, we can! – and this ‘is’ (or should be) awfully shocking. Such primordial moral awareness constitutes a generic sense of human responsibility (Ott Reference Ott, Sierra and Grisoni2017, following Hans Jonas) which requires to address OA from the environmental ethical perspective more closely.
22.4.2 Common Heritage of Humankind
Respect for the well-being of future generations is a primary normative vantage point, which is covered by the common heritage of [hu]mankind (CHM) principle as advocated by Arvid Pardo, Elisabeth Mann Borghese, and others following their lead (Taylor Reference Taylor, Bollier and Helfrich2012; van Doorn Reference van Doorn2021). The concept is anchored in both ethics and international law (Taylor Reference Taylor, Bollier and Helfrich2012). Implications of CHM in UNCLOS are outlined in Böhm and Ott (Reference Böhm and Ott2019). Via a CHM-approach, the former concept of ocean as res nullius is replaced by a res communis-approach (van Doorn Reference van Doorn2021).
Common heritage of [hu]mankind is not grounded in individual rights and entitlements. It would be strange to claim a right on a specific pH threshold of ocean waters. Obligations to future generations with respect to the ocean are twofold pro tanto (Ott et al. Reference Ott, Negenborn, Matz-Lück and Harris2022). On the one hand, the ocean is a planetary entity, while, on the other hand, the chain of generations has no definite end. In consequence, a collective entity called ‘humankind’ has a long-term responsibility against future members with respect to a huge global good called ‘ocean’ and its qualities, resources, and inhabitants. Such responsibilities can’t be reduced to obligations against individual members of future instances of humankind. In any case, the ocean will remain the ocean, but its features, amenities, and disadvantages may become different to future humans.
In principle, we can bequeath (‘pro tanto’) goods and bads to future generations. From OA research (Section 22.2) we assume that OA is not a change by which future generations will be benefitted. Therefore, OA should prima facie be regarded as change for the worse (‘bad’). A bad becomes a moral evil, if it is recognized but remains unaddressed.
22.4.3 Strong Sustainability
Common heritage of [hu]mankind refers to the idea, but not yet to a specific concept of sustainability. To some economists, natural resources and natural capital might be perfectly substitutable by other kinds of capital. According to optimistic assumptions about substitution, the depletion and degradation of natural capital would not be a catastrophe (Solow Reference Solow1974) if prudent investments in man-made capital, social infrastructure, and human capital were undertaken. This approach has been dubbed ‘weak sustainability’. OA might not be a big problem for weak sustainability, since a change in marine pH might be compensated by artificial ways to enjoy the ocean (by cruising ships, digital twins, improved diving and surfing equipment, etc.). Humans may well cope with OA and won’t miss former pH values. They shall conform to shifting marine species compositions.
The concept of strong sustainability denies belief in almost perfect substitutability (Daly Reference Daly1996; Ott & Döring Reference Ott and Döring2008: ch. 3, 4; Ott Reference Ott2014). Thus, natural capital should be held intact over time. The concept of natural capital refers to stocks and non-living and living funds whose different flows contribute to overall human welfare, including so-called eudemonic values (Ott Reference Ott2016; Ott & Reinmuth Reference Ott, Reinmuth and Beckmann2021). Eudemonic values strongly overlap with so-called ‘cultural services’ within the ‘ecosystem services approach’ (Section 22.4.5). If natural capitals have been depleted in the past, society should invest in natural capitals by ways of ecological restoration. Neumann et al. (Reference Neumann, Ott and Kenchington2017) argue that SDG 14 implicitly presupposes strong sustainability. From a strong sustainability perspective, the ocean water bodies are a huge non-living fund of natural capital. This non-living fund is a living condition to a huge diversity of marine organisms nested into complex food webs. A substantial fraction of such organisms may, actually or optionally, belong to living funds of natural capital. Thus, OA is likely to impair fractions of natural capital. If so, OA is not in accordance with the Constant Natural Capital Rule (CNCR) of strong sustainability. If OA violates, impairs, and compromises the CNCR, it should be minimized, as SDG 14 demands (Section 22.3). Following this line of reasoning, we see OA as an imminent encroaching long-term threat to ocean’s natural capitals and the supporting, provisioning, regulating, and cultural services (Ecosystem Services and Cultural Ecosystem Services) that stem from them. Such threat is pro tanto, and there is neither need nor possibility to prove it with respect to every group of marine species. According to the argument, CHM, SDG 14, and strong sustainability are coherent and fit together in a reflective equilibrium.
22.4.4 The Legacy of Aldo Leopold to the Ocean
Two sub-targets of SDG 14 refer to ‘ocean health’ but it remains unclear what ocean health should mean precisely. Literally, the concept of health, whatever its meaning within medicine, applies to organisms only. Therefore, the parlance of a ‘healthy’ ocean is to be interpreted as a metaphor. Metaphors are guiding images (‘visions’). They can inspire our common moral imagination (Weston Reference Weston2012) and may motivate people more strongly than sophisticated ethical arguments. Such metaphors are ‘boundary objects’ since they interconnect epistemic communities, but they can serve as boundary objects best, if they are translated into scientific concepts.
Bohnsack (Reference Bohnsack2003), Neumann et al. (Reference Neumann, Ott and Kenchington2017), and Franke et al. (Reference Franke, Blenckner and Duarte2020) propose to interpret this ‘ocean health’ metaphor in the spirit of Aldo Leopold’s ethical principle stating that actions should respect ‘stability, integrity, and beauty’ of biotic communities within land and sea (Leopold Reference Leopold1977). With respect to ‘ocean health’, this translates to (1) resilience (for ‘stability’), (2) productivity or fertility (for ‘integrity’), and (3) cultural richness (for ‘beauty’) of the biotic community. To Franke et al. (Reference Franke, Blenckner and Duarte2020: p. 559) the ocean is ‘healthy if and only if it is resilient, productive, and diverse’. OA may affect the ocean for worse on all three parameters.
22.4.5 Ecosystem Services
Parameters of ocean health can be specified and, at least in part, measured by the ecosystem service approach (ESA). While there are numerous definitions of what comprises an ecosystem service (see Haines-Young & Potschin Reference Haines-Young, Potschin, Raffaeli and Frid2010 for a detailed review), the general idea behind ESA is to bridge the gap between nature and human welfare. Contributions in Schubert and Müller (Reference Schubert and Müller2023) show how the ecosystem service approach can be applied to marine systems (as the Southern Baltic coast). Natural capital entails stocks and funds which enable beneficial flows. Such flows are dubbed ‘services’, although nature should not be interpreted as service delivering industry. Thus, ‘service’ is a technical term within a concept. The ecosystem service approach bridges the gap as follows: first, a distinction is drawn between nature as such and a concept of natural capital, defined as a broad source contributing to human welfare in many ways. Second, it is assumed that stocks (or funds) of natural capital provide a variety of flows which benefit human beings in different respects. Third, those respects are categorized as:
[Supporting services (e.g. ecosystem structures and functions)]
Provisional services (food, fibre, timber, fish, shellfish, etc.)
Regulating services (water, climate, soil, flood regulation, etc.)
Cultural services (aesthetics, recreation, spiritual, etc.).
The category of supporting services is contested because it consists of ecological functions and structures, which underlie the beneficial flows of the other three categories (Haines-Young & Potschin Reference Haines-Young, Potschin, Raffaeli and Frid2010). Their sustenance is necessary for ongoing beneficial flows, but a separate valuation of supporting services implies double counting (Boyd & Banzhaf Reference Boyd and Banzhaf2007). Thus, they have been put in brackets. There is conceptual connectivity between the Leopoldinian categories (fertility, resilience, beauty) and types of ecosystem services. Fertility refers to supporting and provisioning services that result in measurable yields (fisheries). Richness, diversity, and beauty refer to cultural ecosystem services. Flows can also have opposite effects, that is, cause harm or disadvantage. These are termed ‘disservices’. OA might not only impair services but may foster disservices. For instance, it has been highlighted that there will be winners (including, for example, jellyfish, epiphytic algae, and seagrasses) and losers among marine organisms in response to OA and ocean warming. Ocean acidification in combination with warming and other drivers of ocean change may cause in jellyfish blooms. This could locally interfere with the recreational value of bathing at the coast (Rodrigues et al. Reference Rodrigues, van den Bergh and Ghermandi2013). Algal blooms can be problematic for swimmers’ health. Disservices might impair our admiration and appreciation of the ocean.
22.4.6 Cultural Ecosystem Services
Let’s take a special look upon cultural services. Recreation and (eco)tourism are the most frequently considered cultural ecosystem services in economic studies, because they allow for contingent valuation. However, these services do not fully represent the category of cultural services. Neumann et al. (Reference Neumann, Ott and Kenchington2017) specify the cultural value category with coastal ecosystems in mind:
Aesthetics, beautiful sceneries
Sense of place, feeling at home
Leisure and recreation, health improvement
Inspiration for poetry, painting, and music
Transformative values, virtue enhancement
Spiritual encounters with nature
Cultural heritage
Specific (local, regional) cultural values.
All these cultural services (= eudemonic values) can be realized at sea and in coastal zones (Ott & Berg Reference Ott, Berg, Schubert and Müller2023). Cultural values (inclusive non-western ones) might be encapsulated in narratives, proverbs, songs, festivals, rituals, and so on. Narratives are highly important for the tradition of values, perhaps especially in oral cultures but are often overlooked from a scientific perspective. Cultural values are intrinsic to activities being undertaken for their own sake, such as sailing, swimming, or diving, even if performed by visitors and tourists. Living close to the sea is often a chosen way of life. By intuition, we regret a person who never saw the ocean.
Gains or losses in ecosystem services are often explored from an economic point of view which aims to place monetary values upon benefits derived from ecosystems. It is frequently pointed out that there are limitations to economic approaches and that especially many cultural services are intangible or difficult to quantify (Jax et al. Reference Jax, Barton and Chan2013). The meaning and significance of cultural services must be hermeneutically understood as it touches the background of belief systems (‘lifeworld’). Habermas (Reference Habermas1981) has warned against a presumptive ‘colonization of the lifeworld’. It might count as an instance for such colonization if aesthetics, place-making, spiritual, and transformative attitudes to the ocean are to be represented in an economic cost-benefit-scheme. How to represent awe in $?
In any case, future humankind has a ‘pro tanto’ entitlement to enjoy cultural ocean values even if it is unpredictable how and where such values may actualize. The conjunction of CHM, SDG 14, strong sustainability, and the ESA approach, including the full set of cultural values, constitutes a ‘deep anthropocentric’ ocean ethics within the paradigm of discursive pragmatism. If the primordial moral awareness (Environmental Pragmatism) becomes enriched by these normative building blocks, they may transform such awareness into attitudes and virtues which are reflected in environmental virtue ethics. Sense of responsibility and (biophilic) appreciation of ocean life may converge. Analysis of such transformation by which a terrestrial being can come ‘close’ to the ocean is beyond the scope of this article. The demarcation problem remains beforehand.
22.4.7 Inherent Moral Value of Nature
To attribute the category of inherent moral value (IMV) to a natural being (NB) means to respect this being for its own sake irrespectively of how valuable and beneficial it may be to humans. If such attribution is justified, direct moral obligations hold with respect to NB. The natural being, then, has become a ‘moral patient’. Moral patients are beings, which lack the capability to join moral discourse but are protected by moral rules which imply obligations to moral agents. Such obligations may be obligations not to kill, not to harm, not to violate, not to capture, not to hunt. The problem of how to attribute IMV is called the ‘demarcation problem’. Analysis is given in Ott (Reference Ott, Westra, Bosselmann and Westra2008). The non-anthropocentric (‘physiocentric’) solutions are:
Sentientism (all sentient beings are moral patients)
Zoocentrism (all prehensive animals are moral patients)
Biocentrism (all living beings are moral patients)
Ecocentrisms (all ecosystems as such are moral patients)
Holism (all natural beings are moral patients).
I have sympathies with sentientism, yet I see sophisticated problems in applying sentientism to marine life. Sentientism seems appropriate with respect to marine mammals, sea birds, and even turtles and sharks. If one adopts sentientism, the problem occurs that (most or all) fishes are sentient (Rey et al. Reference Rey, Huntingford and Boltaña2015) Egalitarian sentientism implies a moral ban on fisheries as a rigid conclusion, given the reliance of many coastal communities on artisan fisheries for nutrition. If one wishes to attribute IMV only to some sentient creatures, as marine mammals, turtles, sharks, and so on, one faces the accusation of arbitrariness. If environmental pragmatism conceives sentience as gradual, it is possible to circumvent a complete ban on fisheries. Gradual sentientism allows treating members of different sentient species differently according to other features and traits, as proliferation patterns. Therefore, according to gradual sentientism, a mackerel is morally less considerable than a dolphin, a sardine less than a whale. The impacts of OA to sentient marine life are hard to predict.
OA affects many non-vertebrates without sentience. Some non-vertebrates, however, seem to display kinds of awareness (Rozzi Reference Rozzi2019). It remains doubtful, however, whether minimal awareness is sufficient for membership in the moral community. One would have to adopt a biocentric position in order to respect moral entitlements of all organisms to be protected against the impacts of OA. If one adopts biocentrism, however, one faces the problem of how to overview and assess the impacts of all anthropogenic pressures on the myriads of non-sentient, often single-cell organisms living in the ocean. Ocean life in itself puts a question mark upon biocentric considerability. Reverence for life (Schweitzer Reference Schweitzer1926) is rather a basic attitude toward life than a proper solution of the demarcation problem.
Ecocentrism faces the problem to delineate marine ecosystems. In holism, one has to respect seafloors and ocean waters as such, and it might be mandatory to restrain any kind of human interference with the ocean to a minimum. Holism (Gorke Reference Gorke2003) will consider OA directly from the moral point of view. Holism implies a principle of least possible human interference with nature. It gives IMV to all existing entities. Ocean waters exist. If they are modified by anthropogenic impacts, this is morally wrong in holism. To holism, OA is not just bad, but it is a moral evil in itself. Holism, however, rests on a fallacious justification. Holism states that arbitrariness is not permitted on the moral point of view. Any exclusion of any entities from the moral community should be strictly non-arbitrary. To draw a line of moral considerability (distinguish, exclude) counts as arbitrary until proven otherwise. The burden of proof falls on the side of exclusion, and such burden is specified by a criterion of ontological parsimony (‘Occam’s razor’). Any statement ‘entities E-1 deserve IMV because of their morally relevant features F, while entities E-2 don’t deserve IMV because they lack any F’ is less parsimonious than ‘all entities have IMV’. Thus, holism always wins if one accepts the burden of proof.
On reflection, it becomes questionable whether biocentrism, ecocentrism, and holism are adequate ethical concepts with respect to the ocean and its lifeforms. How to follow the moral demands of some egalitarian sentientism to reduce suffering in nature (Horta Reference Horta2017) if big fish must eat small fish? How to consider all plankton and all marine microorganisms, as biocentrism demands? How to distinguish distinctive ecosystems, as ecocentrism requires, if marine life is in constant flux at the high sea? How to deal morally with the water bodies, sediments, and geological items, as holism demands? Facing the ocean, these ethical concepts are puzzling on ontological grounds. Within the arena of UNCLOS, no agreement on the demarcation problem is to be expected. One should not impose a specific solution on all coastal communities. Moreover, to apply different solutions to the demarcation problem to the impacts of OA to marine life will be highly speculative and conjectural. If there is a reason to keep environmental ethics simple, there is a reason to adopt deep anthropocentrism (Section 22.4.6) at least in the case of OA.
22.5 A New Planetary Boundary: Threshold Problem Revisited
In climate policy, article 2 of UNFCCC has been specified to the goal that GMT warming should be limited to ‘well below 2 °C’. We are now in a position to specify the normative building blocks of deep anthropocentrism (CHM, SDG 14, strong sustainability, ‘ocean health’, ESA) which implies aversion against OA-induced disservices to an analogous boundary. Such boundary might be adopted by UNCLOS, as ‘well below 2 °C’ has been adopted by the parties of UNFCCC. Such a boundary might make sense, even if OA has not yet crossed the planetary boundaries according to the diagrams of the Stockholm Resilience Centre. Such presumptive planetary OA-boundary has to be grounded in environmental ethics (Section 22.4) but must be also based on scientific knowledge (Section 22.2).
At current levels of atmospheric CO2, an overall risk of damaging effects to marine species resulting from the combination of OA and warming is very likely; some foraminifera and pteropods are already affected by decreased calcification. Changes in abundance of these organisms would be relevant for marine food webs. Considering OA in isolation, high-risk levels, by which 30–50 per cent of calcifying species across taxa including molluscs, corals, and echinoderms are affected, are predicted for atmospheric CO2 levels exceeding 500 ppm. Adding effects of ocean warming to the picture, the transition to the high-risk zone already starts above 400 ppm, that is, close to present CO2 levels. Right now, we are at the breach of the high-risk zone. The zone of very high risks is looming beyond. Two thresholds of very high risk to marine life (BIOACID 2017) are characterized by (1) increasing effects on vulnerable taxa, marginalization of warm-water reefs, and loss of fish habitat; and (2) negative effects on more than 50 per cent of molluscs and corals. If the combined effects of OA and warming are considered, two ‘very high risk’ thresholds to marine life overlap and are located at levels around 450 ppm. This indicates that pH 7.97 comes close to the very high-risk margin (Böhm & Ott Reference Böhm and Ott2019). If so, there is only 0.1 distance to the zone of very high risk.
The Stockholm Resilience Centre proposed a planetary boundary for OA based on average global surface ocean aragonite saturation as an indicator, following which aragonite saturation should be sustained at 80 per cent or more of the pre-industrial state, ± natural diel and seasonal variability (Rockström et al. Reference Rockström, Steffen and Noone2009). Personally, I support this planetary boundary for OA. With the legal framework of UNCLOS, there should be further debate on a precautious pH-threshold.
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