Defining established and emerging field developments at the intersection of human health and environmental change

In the following section, we introduce seven field developments identified through an iterative, collaborative process based on extensive literature reviews and engagement with international scholars and practitioners. A ‘field development’ refers to a branch of study that emerged in response to some need for new tools or approaches to understand a given problem, sometimes in the context of a broader discipline (eg, public health). Here, we define each field development, situate it historically and provide example texts (summarised in table 1). The selection of these field developments was based on three criteria: (A) having a traceable scholarly lineage (including keystone publications or stand-alone established communities of scholarly or applied practice); (B) the deployment of specific principles or orienting concepts; and (C) the articulation of specific strategies or methodologies that synergise with either implicit or explicit goals and worldviews.

Occupational and environmental health, a well-established field, focuses on the prevention of adverse health conditions from exposure to biological, chemical or physical hazards in specific settings such as the workplace, home or community. Historical and current occupational and environmental health practice is oriented towards risk assessment, protecting human health and limiting exposure to environmental hazards. It is widely recognised to have emerged in the mid-19th Common Era (CE) during the sanitary public health movement in England.8 The positioning of environments as posing health risks leads to a broad and often institutionalised emphasis on protecting the environment to promote human health, involving classic public health practices such as testing water and air quality and conducting food inspections.9 Although occupational and environmental health rarely extends to the health of ecosystems or protecting non-human species—it acknowledges the need to understand human health in relation to broader ecological, social, economic and political contexts.10 This field works at the interface of various scientific disciplines including (but not limited to) chemistry, biology, medicine, toxicology and epidemiology.11 Collaborations among multiple types of health practitioners such as occupational physicians and safety specialists are seen as necessary to create healthy environments for future generations.10

Political ecology of health is a subfield of the broader field of political ecology12 which primarily focuses on human–environment relationships and power. The subset of practitioners who focus specifically on health in relation to the environment initially referred to their work as ‘political ecology of disease’, combining political economy with disease ecology, beginning in the late 1970s and early 1980s.13 More recently, work in this space has been framed as ‘political ecology of health’, recognising health as encompassing overall well-being and agency, rather than simply the absence of disease or injury.14 Studies may often, although not exclusively, employ ethnographic methods, informed by concepts from medical anthropology and human geography. Key themes in the field include tracing the impacts of unfair power relations on environmental conditions and health; examination of discourses about health generated by individuals, groups and institutions; and analysing the implications of asymmetries in power among humans and non-humans for health and well-being.14

Environmental justice is ‘the fair treatment and meaningful involvement of all people regardless of race, color, national origin, or income with respect to the development, implementation, and enforcement of environmental laws, regulations and policies.’15 It emerged in the 1980s as a social movement in the USA, fuelled by the civil rights movement, as people organised against the disproportionate and therefore unjust siting of hazardous land uses near marginalised (ie, often minority) communities.16 17 This orientation is rooted in the notion that environmental quality and human rights are inseparable, and that ideas about justice should be incorporated into understandings of environmental sustainability.18 19 In health contexts, environmental justice refers to the equal distribution and reorientation of economic, health and environmental systems that empower rather than discriminate against populations. Legal and procedural relationships between health equity and environmental management are a main focus, while action is directed towards three orienting goals: (A) ensuring safe and equitable amenities; (B) influencing decision-making that enables positive health outcomes; and (C) recognising and engaging with the whole community, especially marginalised groups, in health-related decisions.20

Ecohealth adopts systems approaches to promote the health of people, animals and ecosystems in the context of social and ecological interactions.21 Notable developments in this field occurred between 1995 and 2005, drawing on a range of scholarly efforts that called attention to the impacts of ecosystem change on health and well-being. Ecosystem health can be seen as a precursor to the development of ecohealth, including efforts in the late 1990s to define the health of ecosystems in relation to system organisation, productivity and resilience.22 The emergence of ecohealth as a distinct field was influenced by attending to reciprocal relationships among health, ecosystems and society. Thus, ‘ecosystem approaches to health’ demand explicit attention to social and political dynamics, including the role of diverse actors in understanding and responding to ecosystem changes.23–25 This requires careful consideration of past social-ecological approaches to promoting health and the need to explicitly recognise how ecology and ecosystems are foundational to human health.26 Other influences include disease ecology, the study of emerging infectious diseases and their implications for human, animal and wildlife health,27–29 and ongoing attention to social-ecological resilience in relation to public health.25 26 30 Drawing from a decade of case studies of ecosystem approaches to health, Charron31 outlined six key principles of ecohealth research practice as: (A) systems thinking, (B) transdisciplinary research, (C) stakeholder participation, (D) sustainability, (E) gender and social equity, and (F) knowledge to action.

One Health examines and promotes the inter-relationships between human and animal health through interdisciplinary cooperation and communication. With roots in veterinary and human medicine, the intellectual lineage of One Health can be traced back to the mid-19th CE and the concept of ‘one medicine’.32 The field more recently gained momentum in the early 2000s in response to the severe acute respiratory syndrome and avian influenza epidemics.33 One Health primarily focuses on zoonotic disease research, communicable diseases, food safety, nutrition and antimicrobial resistance.34 Veterinary and public health practitioners make up the majority of the field, although One Health is not limited to those disciplines35 and also includes conservation biology and conservation medicine. There is a focus on collaboration, particularly among medicine, veterinary medicine, public health, environmental science36 and, more recently, ecohealth.35 37 38

Ecological public health is a scholarly approach that calls for the unification of physical, biological, social and cultural aspects of health, thereby expanding public health’s multisector approach to health promotion.39 Advocates argue that human and ecosystem health are interdependent and that contemporary political goals of promoting continued economic growth often ignore or obscure emerging threats to long-term environmental sustainability.40–42 Ecological public health emerged in the late 20th CE from a long intellectual heritage attempting to incorporate broader determinants of health across multiple levels of analysis and contexts.43 44 This includes incorporating concepts from human ecology into health promotion activities,45 46 which paved the way to consider ‘eco-social theory’—that is, the intertwined realities of every ecological scale and social context of which health is the product.47 This approach calls for health practices rooted in collective rather than individual efforts, and encourages engaging new actors across levels of influence and action.48 Ecological public health has also been taken up in practice via the Canadian Public Health Association’s ecological determinants of health framework,49 developed in response to WHO Commission for the Social Determinants of Health report,50 which is critiqued for omitting key environmental/ecological determinants of health.

Planetary health is a relatively recent field development that has emerged since 2010. It seeks to understand and promote ‘the health of human civilization and the state of the natural systems that define the safe environmental limits within which humanity can flourish.’1 Planetary health emerged from the Lancet and Rockefeller Foundation report on Planetary Health in the Age of the Anthropocene, and now includes a stand-alone scholarly journal—The Lancet Planetary Health—and a growing international network of colleagues. As a field of inquiry and practice, planetary health situates human health within global biophysical processes, recognising the tight interdependencies that exist between human civilization and the life-sustaining systems of the planet.51 Planetary health is also considered by some as a health movement calling for ‘collective public health action at all levels of society—personal, community, national, regional, global and planetary.’52

Discussion: convergences between emerging and established fields operating at the nexus of environment/ecosystem, animal and human health

Increasingly, there is overlap among the field developments identified in this paper, yet differences in approach and foci remain, reflecting the unique epistemological positions, historical lineages, and the priorities of scientists, institutions and funding sources that shape these fields. While not an exhaustive list, from our standpoint none of the fields listed here are a priori ‘better’ or ‘more useful’ in tackling complex socioecological health problems; instead, each contributes specific strengths and tools to the task of understanding and responding to the health impacts of environmental change.

The most apparent commonality bridging these fields is the explicit recognition of the complex interdependencies among the health of ecosystems, humans and other species. Notwithstanding, the level of integration to holistically understand links between human health and natural systems varies across field developments. More recent fields, such as ecohealth and planetary health, closely embrace the nested nature of multiple scales in driving health outcomes, focusing on the interactions between and within both ecosystems and human societies. Across all fields, this has precipitated a new generation of research methods built around systems-level determinants of health (eg, systems dynamics modelling, multilevel modelling).53–56 The degree to which complex systems thinking is epitomised or mainstreamed into contemporary environmental public health remains debatable, raising the question of how to disrupt existing models of public health to better protect ecosystems and environments. Indeed, while most field developments argue for new ways of thinking or conducting research and call for novel intervention designs that respond to complexity, challenges remain in terms of how this can be achieved.

Equity considerations are also relevant across fields. This translates into questioning what is fair, right or just, and implies critical inquiry into systems that replicate inequitable societal structures and skewed power relations. Advocating for the promotion of health equity, for humans and for other living organisms and ecosystems, is an orienting goal that speaks to the need to question the role of dominant anthropocentric narratives, and to reposition knowledge systems that have traditionally been omitted from conventional public health approaches. Such considerations are particularly strong in fields actively engaged with the politics of science and public health, notably political ecology of health, environmental justice and ecohealth (with its orientation towards social and gender equity). The related disciplinary subfields of medical anthropology and medical sociology also provide guidance for those interested in power and equity.

All fields endorse the importance of working across academic disciplines. This is most evident in intentional engagements between the ecological and environmental sciences, veterinary medicine and public health.35 Increasingly, there are calls to transcend disciplinary boundaries in health research and practice.31 57 Collaborations with an array of likely and unlikely allies—including, but not limited to, grass roots community groups, and stakeholders in the public, private and non-profit sectors—are also gaining importance as a means to share power, reconcile conflicting priorities and intentions, and develop more inclusive and equitable intervention strategies.58 In practice, the form and degree of critical engagement with non-academic actors and multiple scholarly traditions is variable across and within fields. Thus, a core issue remains: how do we deal with diverse (and sometimes incommensurable) worldviews, value systems and methodological orientations? Discussions around transdisciplinarity57 and undisciplinarity59 may provide interesting opportunities to address this question, with mixed methods and participatory research approaches supplying pragmatic tools to conduct related research. This question is particularly relevant to next-generation scholars and practitioners who are tackling increasingly complex environmental issues (eg, health impacts of global environmental change) which necessitate the integration of multiple disciplines, fields and approaches. Overcoming the bias of any single discipline or field should be seen as paramount to the conduct of such research.

As fields evolve, they are faced with the challenge of moving from theory to practice by actively moving across scales and boundaries to understand complexity. Health scholarship, like other fields, has a tradition of adopting a territorial approach that fails to harness the potential of cross-fertilisation and adoption of unfamiliar, although innovative, ideas. True engagement with ecological systems as living entities requires committing to work with people who think and act in diverse ways, and to think about how these systems extend beyond (often arbitrary) governance boundaries designed for human populations (eg, as watersheds, airsheds, bioclimatic zones, and so on). It also entails approaches that do not simply gather specialists to provide ‘expert’ opinion, but to assess issues collectively from various perspectives.

In this sense, a fundamental step forward seems to be participating in processes of (re/un)learning, where public health researchers and practitioners interrogate their underlying assumptions and beliefs, examine dominant narratives and question power structures that persist across field developments. Of note is the responsibility (and not always a strong suit of emerging fields) of being engaged, reflexive, and both inclusive and respectful of history, precedents and intellectual near-neighbours. Indigenous knowledge and perspectives serve as a particular—and often overlooked—exemplar demonstrating rapid and ongoing developments in indigenous leadership and governance for the ecological dimensions of health in relation to other social, cultural, historical and political determinants.60 Indeed, much has been written on overcoming dominant political-economic discourses and cultural imperialism that have separated humans from nature. Finding ways to respect and engage with both traditional wisdom and Western scientific traditions has potential to greatly enhance future research endeavours.61 62