Advancing Planetary Health Through Interspecies Justice: A Rapid Review

Abstract

Planetary health definitions are clear about advancing human well-being, aiming for the highest standard of health worldwide. Planetary health recognizes human health is dependent on natural systems; however, framing human health as the central consideration of planetary health may risk rendering invisible the non-human species that are central to the viability of ecosystem services and human survival. This review seeks to discover and describe opportunities for advancing discourses on planetary health justice through exploration of the interspecies justice literature. This rapid review of forty-three articles asks the following: how does health arise in interspecies justice literature and how can interspecies justice advance broader conceptualizations of justice in planetary health? Results suggest opportunities for epistemological expansion within planetary health to include consideration of other species, ecosystems, and relationships between them. Examining what health is for more-than-humans, reflecting on how we understand these interdependencies, and advocating for decolonizing planetary health study and practice are critical to growing planetary health justice.

1. Introduction

“When we begin to consider what justice might demand in relationships with others, we must ask what their needs are in relation to the pursuit of flourishing.”

Mathieu Dubeau

Planetary health definitions center human well-being, aiming for, “the achievement of the highest attainable standard of health, well-being, and equity worldwide through judicious attention to the human systems—political, economic, and social—that shape the future of humanity and the Earth’s natural systems that define the safe environmental limits within which humanity can flourish” [1]. A hallmark of planetary health is the understanding that human health is dependent on vital natural systems [1,2] and that staying within our environments’ safe operating spaces is essential; however, this is often discursively framed as operating within the limits of those systems for the inherent and perhaps almost sole benefit of humans. Such framings may be criticized for permitting the maximum extraction of natural resources to optimize human health and livelihoods, without considering harms to other species and ecosystems. Paradoxically, despite a core focus on promoting human health, this anthropocentrism renders invisible the myriad non-humans that are central to the viability of ecosystem services and human survival. Furthermore, centering human health without attending to harms caused by human overconsumption, injustice, and conflict makes discussion of living within our planetary boundaries cursory. Thus, while planetary health acknowledges that human health depends on the health of our environments, it is essential to also contemplate what health is for ecosystems, and for diverse more-than-humans therein. Furthermore, consideration is due for who and what are included in the scope and demands of justice (and health), particularly in the context of the ecosystems upon which human health and well-being depend. In this framing, planetary health would benefit from greater theoretical clarity in terms of interspecies justice.

This rapid review asked how the interspecies justice literature might inform the advancement of planetary health justice. In our search of the interspecies justice literature, planetary health only appeared once, in Maric and Nicholls’ publication, which takes a post-humanist approach to physiotherapy, and provides arguments for shifting away from human exceptionalism and towards solidarity with the natural world [3]. Currently, there is no review asking how interspecies justice appears in the planetary health corpus. Given the limited publications concerning planetary health and interspecies justice, particularly as it pertains to the interdependence of human and more-than-human health, there is strong justification for this rapid review. Further justification is provided by the relevance of the project in advancing justice discourses and tangible actions in planetary health.

Interspecies justice is not consistently defined in the literature but generally explores concepts of justice as they pertain to more-than-humans and to relationships between humans and the natural world. By using the term “more-than-human” we intend to presence the myriad species, ecosystems, and other entities that are resident on this planet. The term more-than-human has been used as a generative and open space within which one can learn, explore, and understand relative positionality and draw on these insights to challenge anthropocentrism and center the reality of co-existence with other species [4]. These approaches move individualist-centric theories of some Western thinkers closer to the relational worldviews that have animated Indigenous knowledge, medicine, and conservation for millennia. In other words, these are ancient ideas being described and theorized within the new conceptual arena of planetary health. Clearly, there are diverse epistemic orientations that can be used to conceptualize justice and health. By explicitly identifying and seeking to dismantle cycles of oppression, interspecies justice has the potential to expand the scope of planetary health justice, broadening consideration for who, what, where, and when are included. Interspecies justice additionally offers transformative tools for planetary health practitioners, researchers, and policy makers to engage with justice for the interconnected health of humans, earth systems, and the more-than-human world.

While it may not be necessary, possible, or desirable to completely decenter humans from the work of planetary health, grappling with human exceptionalism is part of advancing justice in this area of work, particularly if the scope of justice is thought to extend to non-human animals, plants, and the environment. This rapid review asks the following: how is health conceptualized in interspecies justice literature and how can scholarship on interspecies justice advance broader conceptualizations of justice within planetary health? Furthermore, the review seeks to consider how interspecies justice could be deployed in service of the evolution of planetary health theories, discourses, and practices of justice. This rapid review of the literature was undertaken during the summer of 2023, with the goal of analyzing the interspecies justice literature and its relevance to planetary health justice.

2. Materials and Methods

This research began with the singular search term “interspecies justice”, and later expanded to include “multispecies justice”, “transspecies justice”, “interspecific justice”, “justice between species”, “more-than-human justice”, and their variations. To refine the scope of our search, and to constrain the quantity of literature managed by a single reviewer, “equity”, “equality”, and “rights” were omitted from our search terms, and this review is limited by their exclusion. Exploration of interspecies equity, interspecies equality, and interspecies rights would undoubtably offer beneficial tools for advancing justice in planetary health and are worthy of future exploration. EBSCO Host, Web of Science, PubMed, ProQuest, JSTOR, and Elsevier-Geobase databases, and Google Scholar were searched with the specified search terms (see Figure 1 and Appendix A).

Search results yielded a total of 114 papers after de-duplication. Abstracts were reviewed and 70 books and articles were removed based on the exclusion criteria. The exclusion criteria omitted books, articles published before the year 2000, dissertations, theses, articles not available in full-text, articles not in English, and articles not including the search terms in the title or abstract. A total of 44 peer-reviewed journal articles were included in the final rapid review.

The literature was analyzed using the web-based literature review platform Covidence (2023). A Covidence spreadsheet recorded if health, well-being, flourishing/thriving, and survival were mentioned and who or what they were describing. Direct quotes were catalogued that (a) describe what health is—including reference to terms well-being, thriving, flourishing, and survival; (b) explore ideas that were relevant to planetary health, or ideas that connect human health and environmental health, species health, or planetary boundaries; (c) discussed justice, including what justice is and who is in the scope of justice, and; (d) explored Indigenous epistemologies, decolonization, and their links to interspecies justice. This research was bolstered by dialogue with the team of authors, but limited as the rapid review was conducted by only one reviewer. Synthesis documents were created and shared with co-authors who are experts in the field of bioethics and planetary health for comment, discussion and analysis.

3. Results

3.1. Health in the Interspecies Justice Literature

Planetary health takes a holistic view of health for all humans, explicitly including well-being, equity, and diverse systems that make up health for the global human population [1]. While health can be defined in a diversity of ways, the World Health Organization’s (WHO) definition states that human health is, “a state of complete physical, mental and social well-being and not merely the absence of disease or infirmity” [5]. Within the interspecies justice literature, health for other species and ecosystems is not clearly defined. Health is embedded in some framings of justice, including Nussbaum’s Capabilities Approach [6], environmental justice, and occupational justice [7]. In the interspecies justice literature, health was discussed directly for other species (13 articles), ecosystems (12 articles), and for humans as an outcome of interspecies justice (21 articles). Because health for other species and ecosystems is sometimes abstract, and because well-being is so clearly embedded in both planetary health and health definitions, we included well-being as a synonym for health. Well-being was regularly considered for other species (16 articles) and ecosystems (11 articles), and Srinivasan describes health as an “expectation of well-being” [8]. As the literature was explored, flourishing and thriving appeared as words that described ideals for species’ (24 articles) and ecosystem’s (14 articles) health and well-being. In some cases, especially for plants, flourishing, thriving, and survival were often considered as a primary metrics of health and justice, therefore the three terms were also tracked and considered as relating to health. Survival appeared in reference to other species (19 articles) and ecosystems (5 articles). Only four of the forty-four articles included in this study had no reference to one of these terms. Interspecies justice offers a perspective that asks who might be deserving of health—humans, other species, ecosystems, and beyond—and what health looks like for more-than-humans. Since health, flourishing, well-being, thriving, and survival appear so frequently in the interspecies justice literature, it could be argued that interspecies health is a central component of interspecies justice.

In the interspecies justice literature, health is most often framed in the way that the health of humans and other species and ecosystems are intertwined [4,9,10,11]. Abundant literature exists on the potential risks that environments pose to human health, including viruses, pollutants, and natural disasters. The interspecies justice literature often shifts this narrative from nature as risk to health, to health benefits humans receive from flourishing natural ecosystems and vital interspecies relationships [12,13]. The focus on interspecies relationships further informs the importance of health for the myriad more-than-human individuals and communities that make up flourishing ecosystems. This framing might help us to reconcile human health’s dependence on the health of non-humans, and the often negative impacts of human health-promoting activities on the well-being of other species and the environment [8].

Reciprocal health benefits and harms become more evident in the explorations of interspecies justice scholars. Humans need to be in contact with nature for healthy growth and well-being [14]. We depend on thriving natural ecosystems for the air we breathe, the water we drink, and the food we eat [15]. Not only do we need nature to thrive as humans, but the harms humans inflict upon nature often cause reciprocal damages to human health, with marginalized human populations most likely to be disproportionately impacted [16]. An example from the interspecies justice literature describes how local farmers and Indigenous people in Vietnam involved in trafficking endangered species often find themselves victims of human trafficking, with corresponding social marginalization, injustice, and health implications [17]. Thus, it could be concluded that systems that condone the mistreatment of animals often also perpetuate injustices and health harms for humans, especially those who are systematically marginalized [18].

The interspecies justice literature that focuses on animals within our food systems often centers human health [18,19,20,21], arguing that injustice for animals in our food systems leads to poorer health outcomes for people [20]. Individuals working in slaughterhouses often have poor health outcomes because of dangerous and polluted working environments. Communities who live near confined animal feeding operations (CAFOs) often experience health harms through exposure to animal waste and pollution; unhealthy animals in these systems may transfer disease to humans (e.g., avian influenza, mad cow disease, and swine flu); excessive antibiotic use in industrial animal agriculture harms human health by promoting anti-microbial and antibiotic resistance [22]; and, the climate impacts caused by this industry threaten the capacity for future generations to live healthy lives [18,19,20,21]. Animals in our food systems provide a particularly good example of how human and non-human health and justice are interconnected and why interspecies justice should be promoted in planetary health justice.

Over half of the articles (25 articles—or 56%) included in this research considered the compounding factor of climate change in the consideration of interspecies justice and health or well-being. While health and healthcare are often framed as locally produced and acted upon, climate change and intertwined human–ecosystem well-being make health a global problem central to planetary health actions [7]. Planetary health’s focus on global human health means climate change and the multitude of health damages forecasted to be caused by climate related events (including harms to individuals, food systems, shelters, livelihoods, clean water, and air) are of great concern. In this light, as climate related events continue to cause harms to the health of humans, ecosystems, and more-than-human others, there can be no separation of our ubiquitous and shared vulnerabilities when faced with the decimation of a livable climate [10,14,17].

While it may be a challenge to decenter the human perspective in the face of injustice and crises, this literature calls for reckoning with human exceptionalism and a return to the understanding that humans are part of the natural world [8,9]. Epistemological shifts are needed to appreciate how the benefits of human industriousness are also connected to the causes and consequences of the earth system crises we now face. Tschakert et al. consider “the numerous, wide-ranging, cross-scalar, and everyday interactions that bind individuals and societies to networks of close and distant others” including other species, and how by changing the livable climate of Earth, we bear the responsibility of potentially killing everything [12,23]. Indeed, at the 2024 Planetary Health Annual Meeting, Rockstrom emphasized that fundamentally, “justice is the right to be born on a livable planet”. Because humans benefit in diverse ways when nature thrives, engaging in the self-serving altruism of extending justice to more-than-humans could be a planetary health climate intervention that benefits human and more-than-human health simultaneously.

3.2. What Is Interspecies Justice?

Justice entails rejecting arbitrary characteristics that determine who is within the scope of justice and how they should be treated, generally moves toward regulatory ideals of equality, and asks what must be fixed and what should remain adaptive in pursuit of justice [24]. Justice is both a normative framework and can guide institutions towards greater equity [9]. Justice is concerned with issues of agency and self-determination, dignity, oppression, access to opportunity and resources, and more [25,26,27,28].

This review explores literature referencing multiple terminologies including interspecies justice (17 articles), multispecies justice (23 articles), and justice for more-than-humans (3 articles) and in each of these terminologies there were no consistent definitions used. While justice is often considered as pertaining to rights and their enforcement, interspecies justice refers to diverse concepts and ideas relating to relationships, needs, desires, worldviews, and more. For example, interspecies justice considers the needs and livelihoods of diverse human and nonhuman life [29]; asks what is needed and what capabilities must be realized to ensure a dignified life for more-than-humans [30,31]; addresses and seeks to rectify harms to more-than-human victims of injustice [16]; links to the arenas of environmental and ecological justice [20,32]; explores moral considerations of ecological wholes and other species [33]; considers justice as fairness, love, and the freedom to achieve well-being across species [34]; attends to intersectional oppression across race, gender, species, and the living/non-living binary [23]; aspires towards a politic that considers a diversity of human and more-than-human life [35]; works as a means to examine and repair relationships between humans and the natural world [11,24,30]; is a concept that requires replacement of human social realms in the whole of nature [8]; generally operates as the opposite of oppression [25]; and acknowledges that current legal and political systems and institutions are poorly set up to accommodate the diversity of more-than-humans in the scope of justice [4].

Use of the word species in interspecies justice requires examination. Celermajer et al. problematize distinctions, binaries, and classification systems like the Linnaean categorization system of classifying species, which is grounded in specific human knowledge practices, and excludes entities like rivers and mountains [24]. Moreover, they warn species classifications carry subjective parallels to concepts like race and sex [24], and perpetuate ideas of separateness that interspecies justice works to deconstruct [9].

The interspecies justice literature examines justice through many ethical frameworks and philosophies of justice, some of which may be useful for advancing justice in planetary health (See Table 1). Many justice frameworks are briefly mentioned, or quickly ruled out of consideration and those are not included here. Celermajer et al.’s article explores several theories of justice and their shortcomings for interacting with justice for more-than-humans [24]. While many justice frameworks are designed for, and clearly only apply to humans, several frameworks for justice explored in the interspecies justice literature offer insights for the inclusion of more-than-humans.

Eight of the articles reviewed engaged with Martha Nussbaum’s capabilities approach for non-human animals [9,24,25,27,30,31,33,34]. Nussbaum’s framework is centered on ten capabilities: Life; Bodily health; Bodily integrity; Senses, imagination, and thought; Emotions; Practical reason; Affiliation; Living in concern for or relation with other species; Play; and Control over one’s environment. Nussbaum argues these components are necessary for sentient, non-human animals to flourish, although Fulfer argues that these capabilities and the idea of flourishing generally could be extended to non-sentient life as well [30]. Health is generally understood as a necessary condition for flourishing. Twenty-four (55%) of the articles considered flourishing for non-human species, while 14 (31%) considered flourishing for ecosystems. Interspecies justice, which centers on relationships that foster individual and reciprocal flourishing for all concerned, often frames flourishing as a means of instantiating justice [25]. Considering Nussbaum’s approach, and notions of flourishing more generally, both offer a conceptual bridge between justice and health. Engaging in activities that promote reciprocal flourishing of humans and more-than-humans offers a means of advancing justice and health simultaneously, rather than one at the expense of the other.

Celermajer and Obrien explore opportunities and barriers for transitional justice as a pathway for repairing relationships that are grounded in historical and systemic violence towards the more-than human world [16]. Transitional justice works to rectify injustice on a systems scale, transforming institutions, laws, governments, political regimes, or educational curriculums to restore dignity and integrity to victims of legacy injustices. This framing is acknowledged as a potential pathway for advancing interspecies justice in three of the articles reviewed [16,24,34]. Transitional justice’s goals often include, “providing accountability for the past, laying the foundation for a just future, and repairing relationships” [16]. Celermajer and Obrien explore how acts of transitional justice, and particularly those that offer symbolic reparation, have the potential to shift norms, boundaries, and codes of conduct within legal and political spheres resulting in transformation of public ethics [16]. Using examples of past and current efforts to repair relationships between post-colonial states and Indigenous people, they propose a pathway for building just relations with soil. This transitional ‘toolkit’ might utilize “trials, truth or truth and reconciliation commissions, restitution and compensation, various forms of institutional reform, apology, memorials and a range of forms of symbolic reparation” to formally acknowledge historical wrongs, and shape precedent for future legal and political action and policy formation in a way that promotes interspecies justice for soil [16]. Their article also acknowledges the role of the private sector in influencing this type of change, and the importance of art as a modality of describing injustices against more-than-humans that many humans may not yet have full understanding of. Such work will additionally require amending myths and narratives that often uphold long-standing systems of oppression and violence, and critical scrutiny of how anthropomorphism has shaped the subject of justice [16,24,34]. If it can be agreed that more-than-humans can be harmed in morally relevant ways, the authors further argue for a change in focus from transforming ideas and other justice norms to changing practices and rethinking embodied relationships [16].

Pineda-Pinto et al. explore how perceptions and attitudes shape distributive and environmental justice, and how justice and injustice are distributed unevenly across species and ecosystems [14]. Using the example of novel urban ecosystems, such as abandoned lots in cities which often support unique species assemblages and thriving unique ecosystems, but are perceived by many humans as unsightly; they consider how human ideas and attitudes shape distributive injustices in these distinctive spaces [14]. Where environmental, distributive, and interspecies justice overlap, human epistemologies, attitudes, and perceptions can perpetuate continued distributive injustices to marginalized human populations, other species, and ecosystems.

The interspecies justice literature also engages with several other common conceptualizations of justice including climate justice [10,23], occupational justice [7], environmental justice [9,11,14], mobility justice [36], social justice [9,37,38] and beyond. Most of these frameworks for justice tend to be human-centric and lack wider consideration that other species, ecosystems, and environments can undergo harm in morally relevant ways [9,11,16]. More-than-human voices, wants, needs, and relationships are broadly absent from these ideas of justice, and there is growing call to rectify this in the reviewed literature. In the interspecies justice literature and across these discursive approaches to justice, there is a clear and consistent call to decenter humans and to consider where interspecies justice is possible [3,11,23,24]. This raises an important question: if we are to expand justice to more-than-human individuals and ecosystems, how do we decide where the scope of justice ends?

Table 1. How justice is discussed in the reviewed interspecies justice literature.

Justice Framework	Definition
Nussbaum’s Capabilities Approach	Eight authors in this review discuss Martha Nussbaum’s capabilities approach to justice, and the ten capabilities she identifies that sentient nonhuman life require to flourish, and which must be secured to meet the demands of justice. These capabilities include 1. Life, 2. Bodily Health, 3. Bodily Integrity, 4. Senses, Imagination, and Thought, 5. Emotions, 6. Practical Reason, 7. Affiliation, 8. Living in concern for or relation with other species, 9. Play, and 10. Control over One’s Environment [6]. Fulfer’s article argues for the inclusion of non-sentient life as also deserving of these considerations, with extension of a capabilities approach to justice for ecosystems [30]. Dubeau cites Nussbaum, naming justice as a primary concern of our relationships with more-than-humans, and flourishing as the justification underpinning their consideration [25].
Transitional justice	Transitional justice aims to redress serious and massive historical wrongs. Celermajer and Obrien consider what this might look like if the victims are more-than-human. Going beyond compensation and rehabilitation, transitional justice aims to rectify injustice on the macro scale, transforming institutions, laws, governments, political regimes, and educational curriculums, to restoring dignity, integrity, and rights to the victims of legacy injustices [16,24,34]
Distributive justice	Distributive justice is broadly about the just distribution of benefits and burdens across groups or populations, often focusing on the just distribution of resources. Distributive justice is sometimes framed as problematic because of its frequent focus on monetary goods and income and lack of attention to processes and relationships that create injustices [25]. Wienhues applies distributive justice to microbes, considering distributive rights to habitat, and effectively engaging with a potential framework for justice that could be expanded to microbes [13]. Six articles reviewed made reference to or considered distributive justice [9,13,14,25,34,39].
Mobility justice	Scott explains mobility justice as exploring how equity and inclusion can be understood through (im)mobilities [36]. This area often combines distributive and procedural justice, with feminist, critical race, disabilities and other diverse perspectives on movement and accessibility. In exploration of how mobility justice might be offered to non-human species, Scott explores mobility justice requirements of domesticated, liminal, and wild species. Yet they acknowledge that the current state of human–non-human relations means that actions to achieve such mobility justice are unlikely [36].
Ecological justice	Ecological justice, while not a search term in this review, includes the concepts of intergenerational (future generations), intragenerational (current generation), and interspecies justice (justice for other species). McLeod-Kilmurray argues that ecological justice could be a tool for moving away from unsustainable commodification of non-human animals, particularly those in our food systems [18]. Guasco’s article concerning extinction narratives positions extinction as a particular concern of ecological justice and extinction studies [32].
Climate justice	Climate justice, while also not defined clearly in this body of literature, is generally concerned with grappling with injustices, particularly those of intertwined capitalism and racism, that result from climate change [34]. Climate justice is heavily criticized by Tschakert for consistently silencing the voices of non-humans, and for centering humans as the species deserving of justice in a world with a changing climate [10,23].
Environmental Justice	Broadly, environmental justice refers to “environmentally linked justice issues affecting humans” [32], including that “environmental degradation violates human rights to life, health, food, and water” [7]. Environmental justice has maintained an anthropocentric focus [34], generally concerned with distributive justice specifically regarding access to environmental resources and the disproportionate distribution of exposure to pollution and environmental harms to structurally and systemically marginalized populations [14]. Similar to climate justice, this concept is criticized by interspecies justice scholars for not including voices, wants, or needs of other species, and for centring humans in discourse [11,23].
Occupational Justice	Kiepek describes occupational justice as the capability of individuals to access and participate in occupations suited to their capabilities and needs for the benefit of individual and collective health and well-being [7]. In Kiepek’s writing, occupational justice is considered intertwined with ecological and interspecies justice, accounting for how human occupations will impact the possibilities for occupations of future generations, the possibility of decentering humans in this space, and engaging with the world in a way that demonstrates good relationship with other species [7].
Social Justice	Social justice, similar to health, is considered something that directly relates to most people’s interests and needs [37]. In the interspecies justice literature, social justice is acknowledged as a field that explicitly considers justice based on class, gender, age, race, ability, and other human framings, but does not generally consider species as equally important [38]. Where this literature examines interspecies social justice is in the consideration of housing justice for older individuals with companion animals [38]. Others argue however, that there can be no social justice without a healthy, functioning, and sustainable natural environment [9].

Search terms, databases, and inclusion/exclusion criteria of interspecies justice rapid review.

Table 1. How justice is discussed in the reviewed interspecies justice literature.

Justice Framework	Definition
Nussbaum’s Capabilities Approach	Eight authors in this review discuss Martha Nussbaum’s capabilities approach to justice, and the ten capabilities she identifies that sentient nonhuman life require to flourish, and which must be secured to meet the demands of justice. These capabilities include 1. Life, 2. Bodily Health, 3. Bodily Integrity, 4. Senses, Imagination, and Thought, 5. Emotions, 6. Practical Reason, 7. Affiliation, 8. Living in concern for or relation with other species, 9. Play, and 10. Control over One’s Environment [6]. Fulfer’s article argues for the inclusion of non-sentient life as also deserving of these considerations, with extension of a capabilities approach to justice for ecosystems [30]. Dubeau cites Nussbaum, naming justice as a primary concern of our relationships with more-than-humans, and flourishing as the justification underpinning their consideration [25].
Transitional justice	Transitional justice aims to redress serious and massive historical wrongs. Celermajer and Obrien consider what this might look like if the victims are more-than-human. Going beyond compensation and rehabilitation, transitional justice aims to rectify injustice on the macro scale, transforming institutions, laws, governments, political regimes, and educational curriculums, to restoring dignity, integrity, and rights to the victims of legacy injustices [16,24,34]
Distributive justice	Distributive justice is broadly about the just distribution of benefits and burdens across groups or populations, often focusing on the just distribution of resources. Distributive justice is sometimes framed as problematic because of its frequent focus on monetary goods and income and lack of attention to processes and relationships that create injustices [25]. Wienhues applies distributive justice to microbes, considering distributive rights to habitat, and effectively engaging with a potential framework for justice that could be expanded to microbes [13]. Six articles reviewed made reference to or considered distributive justice [9,13,14,25,34,39].
Mobility justice	Scott explains mobility justice as exploring how equity and inclusion can be understood through (im)mobilities [36]. This area often combines distributive and procedural justice, with feminist, critical race, disabilities and other diverse perspectives on movement and accessibility. In exploration of how mobility justice might be offered to non-human species, Scott explores mobility justice requirements of domesticated, liminal, and wild species. Yet they acknowledge that the current state of human–non-human relations means that actions to achieve such mobility justice are unlikely [36].
Ecological justice	Ecological justice, while not a search term in this review, includes the concepts of intergenerational (future generations), intragenerational (current generation), and interspecies justice (justice for other species). McLeod-Kilmurray argues that ecological justice could be a tool for moving away from unsustainable commodification of non-human animals, particularly those in our food systems [18]. Guasco’s article concerning extinction narratives positions extinction as a particular concern of ecological justice and extinction studies [32].
Climate justice	Climate justice, while also not defined clearly in this body of literature, is generally concerned with grappling with injustices, particularly those of intertwined capitalism and racism, that result from climate change [34]. Climate justice is heavily criticized by Tschakert for consistently silencing the voices of non-humans, and for centering humans as the species deserving of justice in a world with a changing climate [10,23].
Environmental Justice	Broadly, environmental justice refers to “environmentally linked justice issues affecting humans” [32], including that “environmental degradation violates human rights to life, health, food, and water” [7]. Environmental justice has maintained an anthropocentric focus [34], generally concerned with distributive justice specifically regarding access to environmental resources and the disproportionate distribution of exposure to pollution and environmental harms to structurally and systemically marginalized populations [14]. Similar to climate justice, this concept is criticized by interspecies justice scholars for not including voices, wants, or needs of other species, and for centring humans in discourse [11,23].
Occupational Justice	Kiepek describes occupational justice as the capability of individuals to access and participate in occupations suited to their capabilities and needs for the benefit of individual and collective health and well-being [7]. In Kiepek’s writing, occupational justice is considered intertwined with ecological and interspecies justice, accounting for how human occupations will impact the possibilities for occupations of future generations, the possibility of decentering humans in this space, and engaging with the world in a way that demonstrates good relationship with other species [7].
Social Justice	Social justice, similar to health, is considered something that directly relates to most people’s interests and needs [37]. In the interspecies justice literature, social justice is acknowledged as a field that explicitly considers justice based on class, gender, age, race, ability, and other human framings, but does not generally consider species as equally important [38]. Where this literature examines interspecies social justice is in the consideration of housing justice for older individuals with companion animals [38]. Others argue however, that there can be no social justice without a healthy, functioning, and sustainable natural environment [9].

Search terms, databases, and inclusion/exclusion criteria of interspecies justice rapid review.

3.3. What Is the Scope of Interspecies Justice?

Within the interspecies justice literature, ideas around who falls within the scope of justice are contentious and varied. The worldview or disciplinary focus of the author often appears to shape who is considered as subjects of justice. Scholars consider justice for diverse scales of non-human life including but not limited to non-human animals [7,8,25,26,27,28,31,33,39,40], specific species of animals [36,41,42], extinct animals [32], animal mobility [36], and domesticated animals [16,18,20,21,25,27,38,41]. Some literature broadens the scale to include plants [4,9], entities like rivers and mountains [14,15,36,43], and microbes [12,13]. Others expand the scope of inclusion to whole ecosystems [9,14,15,17,23,30,34,39] and time scales [11,32], which include extinct species and future generations. In consideration of animals, three articles promote justice for sentient life [25,31,39], which is defined in its most basic form as capability of sensing stimuli or the capability of experiencing pain, suffering, or stress. The parameter of sentience has been criticized for being anthropocentric and subjective, and has been used to exclude those who do not demonstrate subjective measures of cognition and consciousness from the scope of justice [30].

Justice for at least some wild animals is generally included in all conceptualizations of interspecies justice. Consideration of justice for domesticated animals is mostly split between companion animals, such as dogs, cats, and horses who live with and work for humans [25,27,38,41], and livestock—animals within our food systems and issues such as their cultivation, care, slaughter and consumption [16,18,20,21,25]. What health is, and how justice is considered in relation to health, differs slightly between companion and food animals, but both often rest on human needs. For companion animals, justice often parallels human justice concerns with animal perspectives; for example, considering mobility justice for animals (dogs permittance on public transit or in bike lanes) and social justice concerns for pet’s allowance in homes and offices [27,36,38]. Those exploring interspecies justice for companion animals also question how domestication may have resulted in (and from) systems of oppression, how the decisions we make on behalf of other species may result in harms and violation of their preferences, and what capabilities and needs our companion animals require to flourish [25,26,27]. Animals in captivity, domesticated or not, exist almost entirely under human control, even though humans often consider these animals their friends or beloveds. Lynch considers how Plato’s Lysis provides insight on how interspecies justice might be improved through more reciprocal friendships and upsetting power dynamics [27]. Scott proposes avenues for mobility justice through citizenship for domesticated animals (e.g., dogs, cats, goats, chickens, pigs), denizenship for liminal animals (e.g., crows) which are species that live near humans in the space between wild and domesticated, and post-colonial sovereignty with freedom of movement for wild species (e.g., orcas). This categorization is focused on meeting the specific movement needs of each group of species [36].

Considering justice for animals in our food systems also focuses almost entirely on human health and more recently labor justice. The humans employed to tend and end the lives of roughly 92 billion animals annually to sustain global meat demands are often themselves oppressed, subjected to low wages and unsafe, and polluted work environments [25,44]. Human food choices are considered in relationship with interspecies justice, reflecting that these choices are embedded in capitalist and colonial systems that limit our options, perpetuate systems of interspecies, intergenerational, and intragenerational injustice [18], and have health implications for humans and animals [20,21]. Since most domesticated animals exist under the complete control of human whims, worldviews, preferences, ideas, and resources—and some of them are arguably the greatest recipients of harms and injustices—they are particularly in need of moral consideration and planetary health and interspecies justice actions.

While justice is considered for plants in some literature, plants were excluded from conversations about justice for species in our food systems, perhaps because of the gross injustices committed against animals in these systems, and because plants are less frequently considered as deserving of justice generally, perhaps because of their perceived lack of sentience. What might justice be for trees or plants? Would justice for domesticated plants differ from those that are considered natural or indigenous to a place? Is justice possible for plants that are considered invasive? In exploring what health is, we included the search term survival (present in 23 articles or 52%), because often living or dying is considered a measure of health for more-than-humans, especially for plant life and microorganisms. In considering the capabilities approach for the flourishing of non-sentient life, Fulfer examines how the basic needs of a tree are essential for flourishing. Access to clean air and water, freedom from physical harms and damages, and interactions with other species are all essential to the flourishing of a tree, which all point to how justice might be experienced by trees and plants [30].

As the literature expands the scope of justice beyond animals and plants to include microbes, there is further evidence that who and what are considered for justice should continually be re-examined based on new information and changing worldviews [24]. Microorganisms including viruses, bacteria, and other microflora and fauna exist within every living being. While some microbiota cause harm, many are essential to the health of more-than-human and human bodies. The human microbiome has been described as so intertwined with human health, digestion, behavior, and neural activity, that humans could be more accurately described as a multispecies collaboration that cannot be alive, rational, or sane without microbes [13]. If we consider this human–microbe relationship, can there be justice for humans without justice for microbiota? In this framing, are humans capable of creating a line amongst species groups where justice should be ceased? And if so, how do we deliver justice to those deemed within the scope of justice when their essential relationships with those deemed outside the scope of justice have been harmed? And how do we decide what kinds of relationships are essential to those who are within the scope of justice?

Examining justice for whole ecosystems, which encompass plants, animals, microbiota, abiotic entities, and more, further broadens the scope of who is deserving of justice. Eleven articles included in this study consider the possibility of justice for ecosystems [9,10,15,17,24,30,34,36,39,43,45]. This framing begins to shift the focus to justice for the whole rather than individual species, and acknowledges that the dignity of ecosystems can be undermined [9,30]. Consideration of justice for ecosystems acknowledges that ecosystems exist as more than the sum of their parts, resulting in the provision of ecosystem services upon which humans depend for well-being and survival [1,39], and offers potential pathways for justice for those considered to be non-sentient or non-living individuals [30]. Justice for ecosystems also rests on the interconnectedness of human and more-than-human well-being [24]. Justice for ecosystems could ensure justice for ecosystem services, Earth systems, and natural collectives of multidirectional relationships.

While justice for ecosystems at first glance appears to include everyone equally, there is potential for individuals to be harmed in the process [24]. For example, some conservation projects cause harm to human individuals by displacing them when areas are protected from humans for the well-being of an ecosystem [24], and individual members of certain species are sometimes culled for the benefit of the ecosystem in the name of conservation [24,33]. Another concern is that justice for ecosystems might result in limited justice for ecosystem services for the primary benefit humans, an example of which can be seen in planetary health pointing to the “safe environmental limits within which humanity can flourish” [1]—an interspecies justice framing of this statement would require the consideration of more-than-human flourishing as well. As such, to be effective for more-than-human interests, justice for ecosystems would include ecosystems as wholes made up of biotic and abiotic constituents, but also consider ecosystems as groups and individuals with multidirectional relationships—and consider justice across scales from the individual to the whole [46]. Justice for ecosystems can further be informed by consideration of essential relationships between animate and inanimate beings as potentially deserving of justice, which further complicates ideas of who is deserving of interspecies justice and planetary health.

The scope of justice can narrow to the individual, as we consider animal rights for a singular cow in the agricultural system, or perhaps each wild individual as is considered in the work of compassionate conservation [33], and broaden to consider groups of species (birds, trees, animals), or other human classifications (domesticated, feral, liminal, wild) [36], and still wider until we encompass specific communities, entire ecosystems and all of their living and non-living components, and the planetary biospheric whole. As we shift in scope, how does justice change? If we include health or flourishing as a metric of such justice, how might justice for the whole advance justice in planetary health? More work is needed to answer these questions.

3.4. Interspecies Justice and Relationships

Some interspecies justice scholars go beyond the who and what, to consider the possibility of extending justice to relationships between species, and between species and their environments [9,16,24,25,28,47]. This is a key contribution to the development of a theory of planetary health justice given its central focus on the ability of humans to live and flourish within earth system limits. Justice for essential relationships and interdependencies recognizes the interconnected nature of our planet, its ecosystems, and the individual species that exist within them. This line of inquiry embeds human and nonhuman individuals and communities in the lands, ecosystems, and places where they exist, and considers that physical damages that harm relationships between an individual or group and their natural ecosystem could be moral harms as well [9]. In this framing, damaging physical, spiritual, cultural or other parts of a relationship between interspecies individuals or between individuals and ecosystems, could be considered a transgression of moral, ethical, or normative standards. Justice for relationships further creates opportunity to extend moral consideration and justice to entities like mountains, rock, soil, and water, which we are dependent on, but are often left out of the scope of justice. For example, when considering health for fish and justice for their relationships, there cannot be justice for the fish without justice for the river, lake, or ocean, since harm to the water will result in injury and injustice to the fish.

Planetary health and interspecies justice are both grounded in interdependence. However, where planetary health focuses mostly on the dependence of human health on functioning ecosystems [1,2,48], interspecies justice considers fair and multidirectional relationships between humans, non-human individuals, collective natural ecosystems, and natural entities like rocks or water [8,9,10,17,18,28,33,43]. In this regard, justice in planetary health could be expanded by epistemic re-conceptualizing of human–nature–other interdependence and relationships. Celermajer et al. and Matevia both offer examples of how describing just interspecies relationships should include the understanding that flourishing ecosystems and healthy biotic and abiotic communities are essential to the health of individuals and their communities, including humans [24,28]. Achieving justice for relationships would require further reflection on which relationships are valuable and to whom, and for what reasons, as well as who and how one should decide when injustice has occurred [24], and regarding how human systems that rectify injustice should be employed. Beyond these considerations, planetary health actions for justice could more explicitly focus on how human health-promoting theories (including health literacy) and actions might benefit the health of other species. Moreover, regardless of the scope of justice at a given time, Celermajer et al. posit that moral consideration should remain a contentious space, continually evolving and adapting as humans deepen their understanding of varied worldviews, species experiences, and relationships [24].

3.5. Decolonizing Planetary Health

There is growing call to decolonize planetary health [14,49,50,51,52,53,54]. Decolonial planetary health aims to center the diversity and importance of Indigenous worldviews, thought, and stewardship, and to acknowledge that Indigenous worldviews of interdependence underpin planetary health theory and scholarship [49]. Like planetary health [49], interspecies justice is fundamentally based on Indigenous epistemologies of interconnectedness and interdependence with nature and more-than-humans. Interspecies justice literatures particularly acknowledge how diverse Indigenous epistemologies reject binaries between humans and the natural world. The literature describes how many Indigenous groups and traditions continue to engage deeply with these concepts, and often have cultural practices and protocols to ensure interwoven ideas of justice are acted upon [11,16,24]. Celermajer et al. acknowledge the Indigenous philosophies that have been practiced for thousands of years which center human–non-human relationships as relational, feeling, and agential, and describe interspecies justice processes as requiring continuous engagement with different ways of knowing and being, maintaining commitment to doing better, and practiced self-conscious decolonization [9]. Decka proposes that efforts at reconciliation and decolonization will likely be unsuccessful without shifting settler epistemologies and ontologies to an interspecies justice ethic of interconnectedness and relationality between humans and more-than-humans [43]. Expansion of justice to include more-than-humans will require diverse ways of knowing, doing, and being [4]. Therefore, Indigenous knowledges enrich how planetary health professionals might conceptualize interspecies justice.

There are abundant examples of how Indigenous worldviews embody and perceive the interdependence and relationality between human health and well-being, and those of more-than-humans and ecosystems. Wiradjuri women of New South Wales, Australia conceptualize links between sick rivers and sick humans, simultaneously understanding connections and pathways between ground and surface waters and how their pathways impact human health [12]. Winter writes of how Māori Mātauranga (knowledge) conceptualizes well-being as resulting from relationships between an individual and other humans, species, and ecologies [11]. Their protocols and practices embody ethics of support, care, generosity, respect, and connectedness to place and multispecies relationships. Māori Mātauranga values all matter and situates the individual as only existing within the context of supportive relationships. The holistic Māori conceptualizations of rivers embody the river’s relationship with the mountain snows and the glacial melt, their silt, sediment, and bedrock, the fish, ferns, and mosses that grow along their banks, and the people who are in relationship with the river—the river is the people and the people hence are the river [11]. The Sami people of the Arctic similarly conceptualize all worldly elements as interconnected, including rocks, rivers, and mountains [15]. In Canada, Mi’kmaq First Nation’s cosmologies see all animals as human relations, and acknowledge that other species experience life in similar ways to humans: “overcoming fears, having adventures, falling in love, raising families” and having a relationship with… the creator” [43]. Clearly, diverse Indigenous epistemologies offer insights on how changes in worldview might alter the scope of justice.

This way of thinking, combined with Western ideas of legal rights, has resulted in the Whanganui River in Aotearoa (New Zealand) (and other rivers) being granted rights, and considered for legal personhood. Although nature’s rights are outside of the scope of this review, some interspecies justice scholars also engage with rights for nature, and rights for nature is a relevant consideration for how justice for other species could be put into practice. Where rights for nature show up in the interspecies justice literature, some tension exists. Fitz Henry describes how some perceive the rights for nature movement as a “new tool of colonisation” that reinforces the conceptualization of nature as property, and could be used to sever Indigenous relationships with the land [37]. Moreover, they posit that rights for nature are incongruent with Indigenous relationships, obligations, and reciprocity with land, whereby people and land are too deeply connected to be considered as individuals with individual rights [37]. As an alternative to nature’s rights, the authors offer that First, Natural, and Aboriginal Law and political arrangements that center traditional Indigenous governance would radically surpass the protections that rights or personhood for nature currently provide to rivers, mountains, and other non-human entities [10,37].

4. Discussion: Advancing Justice in Planetary Health

Our findings show the following: that the health or related terms are represented in most interspecies justice literature; that the health of humans and that of other species are often represented as intertwined; that in many cases the interspecies justice literature focuses on health benefits that other species and ecosystem services provide for humans; and that climate change is often considered as a connecting and compounding factor for interspecies justice and health. The findings also show that the scope of justice is not consistent but includes diverse ideas about justice for more-than-human species, ecosystems, non-living beings, relationships between species and systems, and the need for the continued re-evaluation of justice’s scope. Diverse Indigenous epistemologies offer guidance and examples of more holistic conceptualizations of justice that include all more-than humans, including non-living entities, relationships between species and human’s interdependent relationship with Earth and beyond.

The question of how we can know what health and flourishing are for more-than-humans is valid and should be explored if we are going to cultivate ideologies and practices around health justice for all. Bringing more nuanced attention to what health is for more-than-humans will likely also help to foreground myriad ways that human health is contingent on the health of more-than-human individuals, ecosystems, and abiotic entities. Through the fields of veterinary science, ethology, animal ethnography, wildlife conservation, ecology, biology, and observation by those who care about other species and nature, we already have rich knowledge of what flourishing and health are, or at least what they could be, for more-than-humans and we can draw on this wisdom to work for the well-being, health, or flourishing of all. Where there are questions about what health is, Celermajer et al. draw from Nussbaum’s suggestion of “sympathetic imagining,” combining sympathy and imagination, and activating biocentric wonder to curiously imagine what health, flourishing, and justice are for others and what is required of humans to generate these conditions within which health and flourishing are possible [24]. Where we cannot decide what health is, we can work to avoid inflicting harms on more-than-humans and ecosystems as a first step to upholding health and justice. Planetary health actions are beginning to engage with this space, albeit primarily through the lens of sustainability vis-à-vis emissions reduction for climate mitigation (e.g., considering where healthcare might reduce carbon emissions and waste to reduce harms to ecosystems and climate) [55]. There is clearly more work to be done to change systems where humans benefit from explicit harms to more-than-human individuals and communities.

Based on this knowledge, scholars engaging in planetary health justice can work for a deeper understanding of what it means to cultivate reciprocal relationships with other species and environments based on a common pursuit of good health for current and future generations. Thorny ethical questions will continue to emerge as human societies innovate to bring the social metabolism (flows of energy and materials between nature and societies) in line with planetary boundaries. Planetary health might also follow interspecies justice’s call to develop and grapple with a sense of responsibility and restitution for the harms human activities have inflicted on more-than-humans in the name of human development and health, and require consideration of the consequences of reproducing these harms in the present and future [8,9]. Applying human concepts of physical, mental, and social health [56] to other species and ecosystems could offer additional thinking tools to support the development of a theory of planetary health justice that incorporates equity, reciprocity and accountability in interspecies relationships.

Matevia suggests that extending justice to nonhumans requires a new worldview that rejects individualism and embraces communal, life-centered epistemologies [28]. Winter calls for a shift away from speciesism and a global evolution towards an ethic of respect for nature [11]. Occupational and physical therapists likewise urge decentering humans and transitioning to an ethic of interspecies justice to counter the ethic of human exceptionalism they believe underpins current health crises [3,7]. Many Indigenous cultures around the world provide us with examples of worldviews that perceive interspecies relationships as reciprocal, health promoting, and deserving of justice. While one may question whether worldview predisposes action, or action shapes worldview, some would argue that we cannot effectively achieve planetary health without changing worldviews to reject human exceptionalism, recognize the interconnectedness of all species, expect flourishing interspecies relationships, and hone our understanding of human dependence on Earth’s systems. Worldviews that perceive more-than-humans as equally deserving of justice and health would demand transitional justice actions by governments and institutions to produce systems that value and enable reciprocal flourishing. Advancing transitional interspecies justice in planetary health requires asking how we might teach, research, and learn differently, what institutional, legal, or policy changes we should advocate for, what kinds of government and economic systems we should promote, and what kinds of human activities should be supported, discouraged, or ceased to ensure that human relationships with other species and ecosystems result in reciprocal flourishing.

Decolonizing planetary health first and foremost requires centering and supporting Indigenous voices, research, and leadership, and advocating for Indigenous people to have sovereignty over their traditional territories. Indigenous worldviews are holistic in their scope of moral consideration, including flora, fauna, non-living entities, minerals, and spirit [11]. Re-imagining Western notions of the constituents of health, decentering individualist theories of health in preference for more collectivist notions, and integrating the worldview that individuals can only be healthy where the whole flourishes [11] (a reality illustrated by COVID-19) can further advance decolonial and antisexist practices of justice and health. Moving forward with these approaches in an age of mass extinction, colonial biocultural histories, and climate change will require great shifts in worldviews and decolonial practices, theories, research, and actions [32]. Recognizing and acting to support structurally marginalized and at-risk individuals and communities—not only within human populations, but also across species—will further the goals of advancing interspecies justice practices and epistemologies in planetary health [10,43].

Storytelling is one of the methods capable of changing human worldviews [57,58]. Guasco proposes complexity-aware, thoughtful, interspecies, and social justice forward storytelling as a possible method that can illuminate spaces of restorative justice for more-than-humans [32]. Changing the stories we share, for example by portraying humans as part of nature, can demonstrate respect for other species, negate human exceptionalism, acknowledge where injustices have occurred, and highlight pathways towards reparation and interspecies reconciliation. Engaging with narratives in this way might help humans grapple with extinction of non-humans and envision “potential futures of survival, coexistence and flourishing” and the imperative of this for human survival [32].

Where worldviews stagnate in anthropocentric perceptions, perhaps actions, research, and advocacy can still advance interspecies justice in planetary health. Research in this field has the potential to leverage decolonizing, anti-racist, and feminist discourses that value more-than-humans; meanwhile, however, there are shifts needed to ensure we avoid harms caused by the research on the very communities (human and non-human) that we aim to benefit [12]. Some Western epistemologies and ontologies in research and action, where unquestioned, can lead to harms to fragile microecosystems, more-than-human entities, and marginalized human populations. Neimanis offers the example of how research to “enlighten” knowledge of stygofauna (microorganisms who live in soil) is often damaging to those being studied. The act of studying these microbiota, which often involves digging into their natural soil environments and exposing them to light, often causes harm to their health and well-being which may skew scientific findings [12]. Considering this in relationship to justice in planetary health research, there is need for scholars to consider what harms or damages to health might be inadvertently (or purposefully) inflicted upon other species through research practices. Neimanis invites consideration of how the focus on dominant ways of seeing—such as how research subjects are visualized—can limit what is knowable [12]. Furthermore, questioning, reducing, or eliminating harms that are allowable in the name of science and the reproduction of hierarchical assumptions, for example in studies of animal intelligence, pain, or communication, will further advance interspecies justice in planetary health research.

Considering what tangible steps can be taken to produce a world that is more just for all species, multispecies urban development offers ways of planning and creating systems with other species in mind. Srinivasan urges a shift in focus from how much humans can extract resources from the natural world and still live within our planetary boundaries, to a focus on cultivating how humans live, work, and generally exist on Earth and in relationship with nature [8]. The nascent framework created by Fieuw, Foth, and Caldwell explores what it might look like to embrace greater systemic shifts in how we design where we live, work, and play. More-than-human cities, they posit, will aim for greater biodiversity and conservation, co-existence with healthy more-than-humans, centering nature in cities, and grounding posthumanism in planning, legislation, and development [59]. Centering interspecies health in design could further advance consideration for best practices in planetary health and urban development. This could include innovative “ways of planning, infrastructuring and, where necessary, disassembling built environments in a postcolonial context of reconciliation and geoecological repair” [36]. Systems should also support reducing consumption of nonessential resources and better reuse of resources already in human systems. These innovations offer frameworks for designing human spaces where interspecies justice is a priority, and could be applied to other sectors, such as the development of healthcare environments where other species’ needs can be addressed.

The field of planetary health has responded to human needs for nutritious, accessible, health-promoting foods, while mitigating the environmental damages caused by our food systems through the EAT-Lancet Commission on Food, Planet, Health. EAT-Lancet aims to create food systems that can feed the growing human population (8.1 billion at the time of this writing), while existing within our planetary boundaries. Advocating for a “plant forward” diet that centers eating fresh fruits and vegetables, whole grains, nuts, and legumes, EAT-Lancet offers opportunity to consider interspecies justice in our food systems through a planetary health lens [60]. Because the field of planetary health already acknowledges that industrial animal-based agriculture is the most resource intensive and environmentally damaging part of our industrialized food systems, there is need to advance justice in the planetary health diet through the consideration of justice for the animals, plants, ecosystems, and abiotic entities in our food systems and engaging with what that might mean for changes to human activities, particularly in the over-developed world. Since industrial agriculture causes significant harms to other species, ecosystems, environments, human and animal health, and culturally appropriate foods [20], planetary health professionals promoting a planetary health diet, especially when engaging with those who have abundant food choices, can generate immediate health benefits for humans, animals and environments [46].

5. Conclusions

This rapid review of forty-three articles asked how health is conceptualized in interspecies justice literature, how interspecies justice might advance planetary health justice, and how interspecies justice is understood and could be deployed in service of the continued evolution of the planetary health discourses. Our findings show that health, or related terms, are represented in most interspecies justice literature yet, who falls within the scope of justice is not consistent but rather is expressed through a range of diverse ideas about justice for more-than-human individuals and communities, relationships between individuals, groups, and systems, and identifies the need for continued re-evaluation of who deserves justice. Findings show ample opportunities for advancing planetary health justice by broadening epistemologies in relation to the scope and demands of justice and health, considering what health and flourishing are for more-than-humans, learning and relearning more reciprocal framings of justice, taking actions to decolonize planetary health, grappling with human exceptionalism, and disrupting cycles of systemic oppression. This review offers insights into how refreshing considerations of who, what, where, and when are subjects of justice can enable planetary health practitioners to engage in research, policy, practice and education in ways that promote interspecies justice. Bringing more wisdom, innovation, nuance and humility to research and practice will build capacity to support the flourishing of natural systems and more-than-human individuals, entities, communities, and relationships. It is through this reciprocal approach to health and justice that planetary health will produce the co-benefits of human health and well-being for current and future generations.

6. Future Directions

There is further opportunity to engage in research concerning the role of interspecies justice in planetary health. Such research could include consideration of how interspecies justice might more directly be incorporated into the EAT-Lancet planetary health diet, the ethical ramifications of considering interspecies justice on a planetary scale, and how justice changes as a researcher shifts the scale of their attention. Notably, animals involved in health research were not considered in the interspecies justice literature, so there is need for research and consideration of this contentious and challenging space. This research was approached by exploring how health was framed in the interspecies justice literature; research looking at how interspecies justice is framed in the planetary health literature, and how planetary health practices might include interspecies justice would further advance this line of inquiry.