The health of ecosystems and human health are closely linked. Concepts and initiatives such as “OneHealth,” “EcoHealth,” and, more recently, “Planetary Health” articulate these links.2-4 Those concepts are based on recognizing that there is a relation of interdependence between living organisms, both human and non-human, and their ecosystems. And yet, we are living in a time when human activity is leading to a profound degradation of the environment all around the world. Thresholds that, on a global scale, must not be crossed if ecosystems are to remain intact and not be completely transformed have been identified in nine areas5,6: 1) climate change, 2) the erosion of biodiversity, 3) disturbances in biogeochemical cycles of nitrogen and phosphorus, 4) deforestation and changes in ground soil use, 5) chemical pollution, 6) acidification of oceans, 7) depletion of the ozone layer, 8) the degradation of drinking water, and 9) aerosol pollution. These “planetary limits” (figure 1) make up an inflexible framework within which human activity can play out while still allowing the Earth’s systems to function sustainably as a whole and for humanity to pursue its own development. Yet several of these thresholds have already been crossed or are in a concern-ing grey zone. This is all the more worrying because the relationships that connect these various forms of environmental degradation to one another and to human health are nonlin-ear and complex.
Therefore, while significant improvements in terms of life expectancy and overall health have been made in the past few decades, that progress risks being compromised by the an-thropogenic degradation of the climate and of natural ecosystems.2,7 For instance, the loss of biodiversity, global warming, and soil depletion all risk compromising the sustainability of the food production system. Similarly, climate imbalance and air pollution are responsible for respiratory illnesses and a growing number of deaths around the world. The acute prevalence of heatwaves is already linked to steep rises in mortality amongst elderly people in our part of the world and risks compromising the habitability of some regions on the planet. Bearing this in mind, the Lancet Countdown’s annual reports are sounding the alarm in the face of the major threats to the health of global populations and of future generations that stem from the current global warming and, more generally, environmental degradation trends.8,9
Healthcare workers are thus key witnesses to the harmful impact that these degradations can have on the health of individuals and of the population. Reinforcing the visi-bility of the link between crossing planetary thresholds and health issues can contribute to making environmental stakes more tangible and thus encourage changes in the behaviors of individuals as well as structural changes on the level of community governance. Yet the 2019 Lancet Countdown report reveals that very few people conduct any searches that link “global warming” to “health” on Wikipedia.9 A growing number of editorialists and medical organizations have spoken out about the role that healthcare professionals should play in encouraging people to transition towards lifestyles that are more compatible with planetary limits,9,10-18 but few studies are available about how to put those ambitions into practice, and about how effective doing so is.
While our lifestyles may well be part of the over-exploitation of resources and the degradation of natural ecosystems, it is also clear that a certain amount of health problems that society faces today also result from those same lifestyles. For instance, the acute prevalence of type 2 diabetes, cardiovascular disease, and obesity is related to consuming hyper-processed foods that are full of saturate fats and sugar and to the increasingly sedentary lifestyle of the population, which gets around mostly using motorized vehicles, or struggles to commit to outdoor physical activity.
Given the fact that certain aspects of our modern lives, on the one hand, contribute to climate change and the degradation of ecosystems around the world and, on the other, lead to the growth of so-called “lifestyle diseases,” some changes in individual and societal behavior can directly benefit both human health and environmental preservation. The literature refers to this concept by using the term “co-benefits.” The term is used to describe the direct co-benefits on human health of measures that are aimed at reducing environmental degradation,8,10,11,16-22 or conversely the environmental preservation co-benefits of measures that are geared at promoting health.13 From a clinical point of view, the WONCA (World Organization of General Practitioners/Family Physicians) suggests the following definition: “Every-day choices and key changes that people/patients can make in their own lives to simultaneously benefit their own health and that of the environment.”23 From a more structural point of view, it is a matter of local government choices and structural changes that are favorable to both health and the environment. To be effective, these two perspectives ought to complement one another, to ensure that promoting certain individual behaviors is happening within a structural environment that encourages and bolsters them.
A sustainability society requires human societies, particularly in terms of their relationship to the natural environment, that ensures their long-term stability, and enables human flourishing across generations. This implies keeping the impact of human activities under the ecological limits that the planet can withstand. These planetary limits thus set a strict framework that ought to limit human activity. The concept of planetary limits thus provides a framework for guiding the exploration of the idea of co-benefits within health interventions. For instance, nutritional recommendations could take into account optimal intakes in macro- and micro-nutrients for human health, as well as the various indicators on the environmental impact of various foodstuffs (greenhouse gas emissions, surface area required, freshwater or synthetic input use, etc.).
The aim of using the concept of co-benefit isn’t to entertain a kind of dualism between humans and the natural environment. Given the dependence of humans on ecosystems, to feed themselves for instance, or for regulating the climate, the environmental impact of an action that is carried out to im-proved human health is also beneficial to humans - it is therefore a double benefit in terms of health, rather than a co-benefit that solely affects the environment (figure 2). Nevertheless, the concept of health & environment “co-benefits” allows us to link the long-term benefits of ambitions to reduce our impact on the environment and ecosystems to tangible, short-term effects on public health.24 It can thus contribute to encouraging changes (both individual and structural), by hedging its bets on a systemic account-ing for the costs and benefits of our actions: for the individuals who are directly affected, their community and ecosystems, both in the short term and in the longer term, here and on the other end of the planet. This concept also offers a novel and positive perspective that can allow us to broach questions of environmental sustainability in an interdisciplinary fashion within the clinical practice. This approach thus presents us with an opportunity to accelerate the societal changes that the already highly compromised planetary limits make necessary, and could enable healthcare to play a key role in those changes.11,16,19,20,25 Figure 2 schematically displays the notion of co-benefits.
We have explored the concept of co-benefits in three areas (among others) that are recommended by the WONCA:13 nutrition, active mobility, and ties to nature. Studies show that, within these areas, certain structural changes, as well as individual behavioral changes, that reduce our environmental footprint, provide direct co-benefits for health, which could justify such matters beings broached in a clinical context.
The goal of this work is therefore to explore certain system relations that link together population health, individual health, and ecosystem health. It further presents several tangible tools for approaching environmental questions within a clinical context. Despite there being many questions that remain in this area, the tracks that are outlined could make it possible to begin thinking about how to move our societies in the direction of greater sustainability through a new vision of health & environmental co-benefits. We will discuss the lever that health services can function as when it comes to changing individual behaviors, all while recognizing the limits of individual behavioral adaptations in the face of the challenge of sustainability. With this in mind, we also explore the structural measures that could accompany these types of interventions.