Today at COP28 is the first-ever dedicated Health Day in the international climate negotiations, which has the potential to highlight how climate change is harming our health, and the health co-benefits of tackling climate change. Lei Bian and Elizabeth J Z Robinson outline some of the key issues.

The first Global Stocktake is set to conclude at COP28 – a review of how countries are progressing in the implementation of actions outlined in their nationally determined contributions (NDCs) to the Paris Agreement. Preliminary results of the Stocktake have already been published and show that countries’ existing efforts are insufficient to achieve the Paris temperature targets. Our collective poor progress is leading to more weather extremes and higher temperatures, and is increasingly harming human and ecosystem health in complex and interconnected ways. Indeed, 2023 has been the hottest on record, with serious consequences for people and wildlife: the average global temperature is likely to have reached 1.5°C above pre-industrial levels this year.

Interrelated challenges of climate change, health and the environment

Extremes of heat due to climate change are increasing the incidence of heat stress and heat stroke, worsening heart disease and acute kidney injury, and increasing mortality from non-communicable diseases (NCDs), such as cardiovascular, cerebrovascular and respiratory diseases. This is leading to greater healthcare and economic burdens, particularly in countries that have ageing populations. Further, emerging health threats such as zoonotic diseases, antimicrobial resistance and exposure to microplastics have been worsened by the triple threat of climate change, environmental degradation and biodiversity loss. For example, warming oceans can accelerate the replication of marine bacteria, linked to an increase in outbreaks of Vibrio infections

Food insecurity is also exacerbated by extreme heat and drought, through impacts on crop yields, labour capacity, livelihoods in resource-dependent communities, disrupted supply chains, and food access. Combined with climate-change-induced changes in the spread of diarrhoeal diseases, reduced access to clean water for sanitation and hygiene, and lower nutritional quality of some grains, these factors are increasing the risk of malnutrition, including stunting and wasting.

An increase in sea surface temperatures is threatening marine food yields, making fishing communities in lower-income countries particularly vulnerable to socioeconomic determinants of poor health, such as loss of jobs and income, and widened inequalities.

Heat stress is also reducing the number of hours during which it is safe to work and do physical activity outside. The health and wellbeing of workers, particularly in the high-exposure sectors of agriculture, construction and manufacturing, are undermined through an increased prevalence of heat-related illnesses, workplace injuries and reduced work productivity. In 2022, heat exposure led to the loss of 490 billion potential labour hours globally, with nearly 40% of this loss occurring in India. In the same year, the associated potential income losses in lower-income countries were equivalent to 6.1% of their GDP. The number of hours each day during which it is safe to exercise fell  the most in Cambodia and the Philippines.

Countries with large and/or rapidly ageing populations, including China, India and the US, are particularly vulnerable. Ageing has already been identified as a global economic risk, leading to a sharp rise in government spending on pensions, and health and social care. Healthy ageing can be considered an important climate adaptation strategy, as promoting healthier behaviours can increase older people’s resilience to impacts such as extreme heat, in turn reducing pressure on health and social care and improving labour force health. Without taking into account climate change as a systemic risk, the progress already achieved in improving people’s health might be reversed, and any future efforts linked to healthy ageing diluted.

Creating a healthier living environment through reduced exposure to environmental pollution, improving access to nature, including blue and green spaces, and encouraging behavioural change towards healthier lifestyles through increased physical exercise and healthy eating, is becoming harder in a climate-insecure world. Climate change and air pollution are both drivers of biodiversity loss, which in turn is increasing the transmission of infectious diseases and pathogens from animals and the environment to human health. Emerging evidence shows that the combined impacts of extreme heat and air pollution increase the number of deaths disproportionately. Further, air pollution, unhealthy diets and physical inactivity are three major risk factors for NCDs.

Global governance in climate, health and the environment

Climate change adaptation and mitigation, and health and healthcare, can be conceptualised as global public goods, and links between them are starting to be explicitly recognised in global governance. The World Meteorological Organisation’s Early Warnings for All initiative calls for increased climate adaptation investments in early warning systems, which can minimise loss and damage to protect vulnerable and ageing populations. Under India’s G20 Presidency, the joint Development Bank Working Group for Climate-Health Finance is anticipated to play a vital role in mobilising resources to address shortfalls in financing for climate adaptation and crossovers with health. And the COP28 Declaration on Climate and Health is expected to be endorsed by member states to set out a global roadmap and opportunities, with a key focus on the three priorities of cross-sectoral collaborations, climate-resilient health systems and financing.

These initiatives are a promising start to addressing the interactions between climate, the environment and health and set the stage for a focus on building health system resilience at COP28.  

Identifying and acting on health co-benefits from a just transition to net zero

Building on this increasing cooperation, an improved understanding is needed of the climate-health-environment nexus and a sense of urgency to undertake decisive actions to reduce pressure on health systems from the growing burden of disease. National governments, working with partners, can lead interventions by mobilising capital towards investments centred on healthier living environments, healthier livelihoods and nature-based solutions, that improve environmental sustainability.

A more holistic approach can promote solutions that integrate climate mitigation and adaptation strategies, and natural capital, into economic development and poverty reduction. The potential health co-benefits from tackling climate change can be felt in four critical areas: reduced air pollution, active travel, healthy low-carbon diets, and urban greening. Mainstreaming health into a just transition approach – in other words, routinely making interventions that restrict harm to health that might be caused by the transition to net zero and climate resilience (such as the toll from job losses as the energy sector transitions away from fossil fuels, or as the agricultural sector transitions away from livestock and dairy farming) – can support and accelerate the development of sustainable energy and food systems. This requires collaboration between stakeholders such as health, economic, fiscal and monetary authorities, and increased investment in health-determining sectors including energy, transport, building and agriculture, and urban settings.

Accelerating a shift to low-carbon and more plant-based diets, including reduced meat production where appropriate, can contribute to improved food security and provide health and climate mitigation co-benefits. Reducing livestock production can reduce methane emissions, while freeing up land to support carbon sequestration and biodiversity conservation, and for crop production for direct human consumption.

In parallel, adopting a ‘One Health’ approach, which recognises that the health of people is closely connected to the health of animals and our shared environment, can highlight the role of nature and the oceans in tackling the climate crisis. For example, investing in urban green spaces can contribute to reducing mortality among older people, especially those who might not have access to cooling during periods of extreme or prolonged heat, by providing a counter to the urban heat effect.

Improved marine food security can promote healthy ageing across the life course by building sustainable blue food systems, comprising fish, aquatic plants and algae, that are rich in protein and micronutrients such as zinc, iron, vitamins and omega-3 fatty acids. Investing in blue carbon habitats such as mangroves also has the potential to store larger quantities of carbon compared with terrestrial forests. These types of nature-based solutions can provide an important source of food and income for local communities, while strengthening health resilience to climate-related disasters, reducing biodiversity loss, and contributing to climate change mitigation.

If future policy priorities on climate and health were to increasingly focus on the implications of climate change for population health, it could make more resources available for a health-centred just transition. Considering the health co-benefits and associated reduced costs that come from climate action, there is an even stronger case for the multilateral development banks to further align their financial flows with the 1.5°C target, scaling up finance for climate adaptation and mitigation and to protect the oceans. Looking forward, countries could incorporate and reflect the health arguments of a just transition to net zero more broadly into the revised NDCs thatare due to be submitted by 2025.

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