Climate change may be the greatest public health threat of the 21st century (Romanello et al. 2023). Climate change is already plausibly to blame for increasing the frequency of deadly natural disasters, aggravating air pollution, and exacerbating the spread of infectious diseases. With a temperature increase projected to reach the 1.5°C limit in a few decades and 3°C by the end of the century (IPCC 2021), the negative health impacts of climate change will only intensify.[1] The key question then is how to promote and protect population health in the face of climate change.
In this chapter, we address two issues related to the interplay between climate change and population health. First, we focus on the potential “health co-benefits” of climate change mitigation and discuss why recognizing, comprehensively measuring, and accounting for these co-benefits can spur timelier and more effective climate action. In particular, we highlight how a proper assessment of health co-benefits can address two of the main economic and policy challenges of climate change mitigation: the intergenerational issue and the free-riding problem. Second, we argue that health is often undervalued in economic assessments of climate change, despite the growing evidence that, much like education, population health promotes economic growth and wellbeing (Bloom and Canning 2003). This implies that (i) we need to rethink what exactly is the full value of population health and how to quantify it better, and (ii) accounting for the potential broad social and economic benefits of improving population health strengthens the case for near-term climate action.
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That climate change frequently impinges on population health is now well understood (WHO 2021). For example, climate change is expected to intensify the risk of extreme weather events such as droughts, wildfires, heat waves, tropical storms, and floods. A recent report from the World Economic Forum estimates that floods, heat waves, and droughts will cause 13.3 million deaths globally by 2050 (WEF 2024). In addition to widespread destruction and death, extreme weather events also lead to soil and water degradation, which increases the risk of foodborne and waterborne illnesses. Considering that an estimated 2 billion people currently lack access to safe drinking water (WHO 2022) and that unsafe food already causes 600 million cases of foodborne illnesses and 420,000 deaths per year (WHO 2015), the increased risk due to climate change will exacerbate an already daunting problem. Furthermore, climate change will likely impose a significant long-term mental health burden due to the cumulative effects of grief, displacement, and the loss of livelihoods (Obradovich et al. 2018).
Climate change is also expected to reduce agricultural, fishery, and aquaculture yields and disrupt the food supply, leading to volatility in food prices and thereby causing further illness and death. For example, the Intergovernmental Panel on Climate Change’s special report on climate change and land projects up to a 29% cereal price increase by 2050 due to climate change, putting as many as 183 million more people at risk of hunger (Mbow et al. 2019).[2] The most recent Food and Agriculture Organization report estimates that between 691 and 783 million people (nearly 10% of the world population) already faced hunger in 2022 (FAO et al. 2023).
Rising temperatures and changes in precipitation patterns are expected to substantially increase the risk of infection by vector-borne diseases, such as malaria, dengue, Zika, and yellow fever, in many geographies (Thomson and Stanberry 2023). Globally, vector-borne diseases account for more than 17% of all infectious diseases and cause more than 700,000 deaths annually (WHO 2020).
Finally, climate change is increasing the burden on already strained healthcare systems and medical resources. The combination of climate change-induced secular increases and episodic surges in the demand for healthcare will impede the ability of health systems to provide timely and quality care for many health issues and impose potentially crushing fiscal burdens (WEF 2024). Just to give a concrete example, when Hurricane Maria hit Puerto Rico in 2017, it inflicted severe damage on manufacturing plants that produce IV bags, sparking a shortage of those bags in the United States (Mazer-Amirshahi and Fox 2018).
Compounding these challenges, disadvantaged populations – due to geographic location, pre-existing health status, and access to health and economic resources – are likely to bear the brunt of the health impacts of climate change (Hallegatte et al. 2016). Such populations include people living in low-income countries and on small islands, children and older adults, ethnic minorities, poor communities, and migrants. Notably, and unfairly, these are also the populations that have contributed the least to the accumulation of greenhouse gas emissions (Chancel 2022).
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To explain countries’ apparent lack of action (or insufficient action) against climate change, the classical economic framework highlights two aspects of climate change that impede intervention. First, climate change reflects a tragedy of the commons (Ostrom 1990). Because the climate change effects of greenhouse gas emissions have no borders, the cooperation of all countries is needed to solve the problem, but some countries may decide to wait for – and free ride on – the climate change mitigation efforts of other countries (Nordhaus 2015). Second, climate change is characterized as both an intergenerational justice problem and an intragenerational justice problem. As an intergenerational justice problem, the current generation bears the burden of change and cost while future generations reap the benefits (Broome 1994). Thus, a generational bifurcation exists between who pays the costs and who enjoys the benefits. Climate change is also an intragenerational justice problem, as the world’s poor are expected to bear the brunt of a changing climate, which may further reduce the incentives of wealthy nations to tackle the climate change problem.
Stressing the health co-benefits of climate change mitigation can help stimulate the design and implementation of interventions that address the dual challenges of the free-riding problem and the justice problems. Indeed, the major sources of climate change coincide with some main drivers of current poor population health. As a consequence, slowing the pace of climate change will deliver substantial health co-benefits, in addition to myriad non-health benefits such as the preservation of biodiversity and the preservation of physical capital and infrastructure.
Let us consider three specific examples. First, the sectors that contribute the most to greenhouse gas emissions, like transportation and energy, are – intuitively – the greatest sources of air pollution, increasing the risk of cardiovascular diseases, respiratory diseases, cancers, and dementias. To give an idea of the potential magnitude of the health co-benefit of retooling these sectors, recent estimates suggest that fossil fuel air pollution accounts for 5 million deaths per year (Lelieveld et al. 2023). That means that transitioning to greener energy sources by, for example, incentivizing the use of electric vehicles will not only mitigate future climate impacts but also improve air quality and save numerous lives over the next few decades.
Second, the Food and Agricultural Organization indicates that meat and dairy production contributes roughly 14.5% to global greenhouse gas emissions (FAO 2016).[3] The prevalence of red meat – and processed meat-based diets are also major risk factors for chronic noncommunicable diseases such as type 2 diabetes, coronary heart disease, and colorectal cancer (Kennedy et al. 2024). Thus, especially in higher-income countries, transitioning to plant-based diets can reduce both greenhouse gas emissions and the growing burden of noncommunicable diseases (Laine et al. 2021). Estimates suggest that the monetized value of health improvements from dietary changes could be comparable to, and possibly larger than, the environmental benefits of the avoided damages from climate change (Springmann et al. 2016).
Third, urban planning that focuses on car transportation encourages a sedentary lifestyle and increases the risk of noncommunicable diseases (Rutter et al. 2024). By contrast, urban planning that promotes safe walking, cycling, and the use of public transportation contributes to a healthier lifestyle while mitigating climate change (Sharifi et al. 2021).
Importantly, the health co-benefits of climate change mitigation will be substantially experienced (i) in the near and medium term (especially clean air); (ii) locally; and (iii) disproportionately by disadvantaged populations, as those suffering the most from poor health are also those who suffer the most from the health impacts of climate change. The last feature adds to the moral imperative of addressing climate change. The first two features – the near-term and local nature of health co-benefits – imply that stressing the health co-benefits of climate change mitigation can encourage a more urgent policy response.
First, because health co-benefits are near-term, some benefits of climate action can be realized immediately, allowing both current and future generations to gain from responsible climate policy. Thus, the narrative that the current generation pays the costs and the future generations reap the benefits no longer applies. Everyone, now and in the future, benefits from aggressive climate action.
A few modeling studies have demonstrated this result. For example, Scovronick et al. (2019) develop an integrated climate-economy model with an air pollution component and report that failing to acknowledge near-term air quality health co-benefits results in an optimal climate action policy that has net costs for much of this century and that will not keep the temperature increase below the 1.5°C limit. When accounting for the health co-benefits, optimal climate policy is more stringent and will have immediate and continued monetized net benefits – upwards of trillions of dollars annually worldwide. Similarly, Markandya et al. (2018) find that air pollution health co-benefits far outweigh the policy cost of achieving the mitigation targets set in the Paris Agreement.
Second, because health co-benefits tend to be local in nature, they do not suffer from the tragedy of the commons and free-riding incentives. Only cities and states that implement some form of climate mitigation can reap these health co-benefits. This implies that health co-benefits may enhance the potential efficacy of gathering local support for climate policies. As an intuitive example, by incentivizing the use of green energy sources in place of fossil fuels, governments can improve air quality for their citizens – a local benefit – while simultaneously providing climate benefits for the whole world.
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Focusing on population health and in particular on the health co-benefits of climate change mitigation will naturally drive more urgent climate action. Moreover, the complementary message that investing in population health is good for the economy magnifies the case for climate change action.
Let us take the example of clean air once more. Clean air promotes health, but by improving population health, clean air also creates a sequela of economic benefits. These take the form of improvements in concentration, learning abilities, and educational outcomes among children, which in turn lead to better labor market opportunities, higher wages, more human capital, and more robust economic growth. Clean air also increases labor force participation and labor productivity and reduces the healthcare costs of treating respiratory conditions, eye infections, and other chronic illnesses. These reductions will lead to lower fiscal pressure and more economic growth. The same story can be told for the other health co-benefits previously mentioned, like encouraging healthy lifestyles and reducing the burden of noncommunicable diseases. These changes also have sizable, quantifiable economic implications.
For decades population health has been substantially and widely undervalued by economists (Bloom et al. 2004; Ferranna et al. 2023). The undervaluation is rooted in economists’ failure to reckon with the fact that health not only has intrinsic value but also has instrumental value. Intrinsic value refers to the fact that actual and prospective states of good health are enjoyed for their own sake. By contrast, instrumental value refers to the fact that good health enhances our capacity to gain other things of value, for example, by improving our ability to work productively and earn income; to attend school and augment our knowledge, skills, and productive potential; and to look after our children and grandchildren and contribute to their wellbeing. The bottom line here is that the benefits of climate change interventions will encompass gains in human health and the social and economic gains that follow from those health gains.
Accounting for the social and economic sources of benefits is conceptually appropriate and technically feasible. Doing so greatly magnifies the estimated returns to climate change interventions, thereby strengthening the case for such interventions. It also emphasizes the economic value of investing in population health and allows the calculation of rates of returns and benefit-cost ratios, which is the natural language of ministers of finance and planning and other policymakers who hold the power of the purse. Also worth noting are the recent innovations in economic evaluation methods that incorporate distributional equity concerns and allow for the calculation of distributionally sensitive rates of return and benefit-cost ratios, which are crucial ingredients in remediating the inequities of climate change impacts (Adler and Norheim 2022).
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Climate change is already imposing substantial economic, social, health, and environmental costs on the world. Accounting for these costs is appropriate to the design of current climate change mitigation policies and rationalizes more aggressive interventions. For example, reducing greenhouse gas emissions will deliver sizable near-term, local health co-benefits. Such health co-benefits not only have intrinsic value but also instrumental value that is conferred to virtually every aspect of our lives. They can promote economic growth and wellbeing through their impact on labor force participation, productivity, education, and healthcare costs, and on nonmarket productive contributions such as childcare. Accounting for these economic and social implications provides a strong argument for policymakers to invest in population health and contribute to the climate change fight.
Acknowledgments. We would like to thank Dr. Jeremy Farrar, Cardinal Peter K.A. Turkson, and all the participants at the 2024 Summit From Climate Crisis to Climate Resilience for insightful discussions. We also thank Joseph Knee for helpful comments.
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[1] The 1.5°C threshold represents the level of warming above preindustrial temperatures that the signatories to the Paris Agreement have agreed to try to respect (IPCC 2018). The Paris Agreement was signed in 2015 by 196 parties at the 21st United Nations Climate Change Conference in Paris, France.
[2] Across the Shared Socioeconomic Pathways 1, 2, and 3, the median price increase by 2050 is 7% (range 1-29%). This corresponds to a median increase in the number of people at risk of hunger by Shared Socioeconomic Pathway equal to 8, 24, and 80 million, respectively (range 1-183 million). The wide range in price increase and in additional people at risk of hunger depends on differing model assumptions.
[3] The greenhouse gas emissions associated with animal-based foods are due principally to land management (e.g., cutting down trees to create grasslands), enteric fermentation (methane emissions during the digestive process of cows and sheep), manure management, and chemical fertilizers used on crops for cattle feed (Xu et al. 2021).