The 2024 small island developing states report of the Lancet Countdown on health and climate change

The 2024 small island developing states (SIDS) report for the Lancet Countdown on Health and Climate Change expands on the global Lancet Countdown 2023 and 2024 reports to explore the unique contexts, geographies, vulnerabilities, and needs that shape the evolving links between health and climate change in SIDS in the Pacific, Caribbean, and Atlantic, Indian Ocean, and South China Sea regions. SIDS were first recognised as a distinct grouping of island nations at the 1992 UN Conference on Environment and Development; they share high vulnerability to extreme weather events, climate change, and global economic shocks. The message of the global Lancet Countdown is echoed in this Lancet Countdown report for SIDS: a health-centred response is essential to allay the severity of the encroaching impacts of global climate change on the health and wellbeing of populations. Such a response requires international action from high-income countries to reduce greenhouse gas emissions. This action, in conjunction with other locally and internally driven efforts, should enable a prosperous future for the SIDS, which collectively have low emissions.

The past 9 years (ie, 2015–23) have been the warmest on record globally, and populations across SIDS have been exposed to increasing summer temperatures. The consequences of heat exposure to human health are thus acutely prominent in SIDS. During the record-breaking summer heat of 2023 alone, infants (ie, aged 1 year or younger) experienced 48 times more heatwave days than the annual averages for 2000–04. Furthermore, across SIDS since 2019, there have been 14 additional days of per-person exposure to heatwaves for both infants and adults aged 65 years or older—two age groups particularly vulnerable to short-term and long-term complications associated with heatwaves. On average between 2018 and 2022, people aged 65 years or older in SIDS were exposed to 103 days per year of health-threatening heat, up from an average of 53 days per year between 1998 and 2002. As a result, this population was at increased risk for complications of mental and physical health and increased risk of death for more than 3 months per year. The number of deaths attributable to heat in 2017–22 was double that in 2000–05. These heat-attributable excess deaths can also be translated to monetary losses, with losses equivalent to US$647 million incurred across SIDS in 2020.

Addressing heat through adaptation efforts would be an extremely effective and life-saving intervention in SIDS. However, only one of the projects addressing heat-related risks that was approved by the Green Climate Fund between 2015 and 2023 was inclusive of SIDS (focused on cooling facilities). Revamping and upscaling locally appropriate heat-adaptation strategies requires accelerated implementation of surveillance and early-warning and response systems. Of 29 SIDS responding to the WHO Health and Climate survey (2021), only six had early-warning systems in place for heat-related illnesses. Surveillance of cardiovascular, neurological, and psychological conditions sensitive to heat remains inadequate. In addition to these systems, urban green spaces can provide local cooling benefits and alleviate heat exposure in cities. Exposure to greenness and spaces for leisure and physical activity can also lead to improvements in physical and mental health and reductions in overall mortality. There has been some progress in greening urban spaces across several SIDS, primarily via transforming areas of low greenness into areas of moderate greenness. However, these modest incremental improvements have not alleviated high urban temperatures.

The growing risk of heat exposure has become one of many prominent economic pressures affecting SIDS. Labour productivity and healthy lives are undermined by increasing temperatures, with more than 4·4 billion potential labour hours lost in 2023, compared with an annual average of 2·5 billion hours in 1991–2000. In 2022, reductions in labour capacity from health-threatening heat exposure brought potential earning losses equivalent to 2·1% of the average gross domestic product of SIDS. In labour-intensive sectors—eg, agriculture, construction, and tourism—profound changes in occupational standards, such as staggering work hours to reduce heat exposure, should be considered to preserve workers' health and to maximise productivity.

The burden of human-induced climate change has also affected food security and physical activity patterns across SIDS, with detrimental consequences for health. Compared with the annual average in 1981–2010, in 2022 an additional 2·6 million people reported moderate or severe food insecurity as a consequence of drought and heatwave days. The risk of undernutrition, especially in low-income and middle-income households, is being exacerbated by climate change. In SIDS, there are worrying long-term trends towards import-dependent processed diets and associated high morbidity and mortality attributable to chronic non-communicable diseases as a result of these carbon-intensive, unhealthy diets. The widespread health effects of food insecurity and increasing reliance on unhealthy foods are further compounded by the reduced potential for outdoor exercise: even low-intensity physical activity in SIDS was associated with more than three times more risk for extreme heat stress in the past 5 years compared with in 1991–2000. However, there are opportunities in SIDS to transition to more resilient and sustainable agricultural systems and to improve overall health outcomes by embracing healthier, more plant-based diets, with reduced consumption of carbon-intensive red meat and dairy products that increase the risk of chronic disease.

Health systems are not climate-ready

Total land area affected by extreme droughts in 2014–23 compared with 1961–70 has expanded by nearly 30%. More severe and frequent droughts destabilise food systems and contribute to infectious disease proliferation in SIDS, further burdening health clinics and hospitals. Of the 24 SIDS surveyed, 20 (83%) had surveillance systems for infectious and food-borne diseases, which provide essential data for climate and health assessments.

Altered temperature, rainfall, and humidity combinations across all SIDS have resulted in a 33% increase in the transmission potential for dengue compared with the 1950s, and there have been more frequent outbreaks of the disease since 2019. 24 (75%) of 32 SIDS surveyed reported having health-care systems with high or very high capacities for responding to and managing public health emergencies, such as dengue outbreaks. However, data suggest that SIDS are still lagging in the identification and management of the growing climate-related risk of infectious-disease transmission: only five (8%) of 59 SIDS have developed national health and climate strategies or plans, only nine (15%) have done climate and health vulnerability assessments, and only six (10%) have surveillance systems that integrate meteorological parameters with health. Furthermore, the few climate and health vulnerability assessments that have been done have not strongly informed health policies. Climatic shocks have the potential to overwhelm improvements in health-care provision, especially given the complex interactions with climate-sensitive diseases (eg, non-communicable diseases, infectious diseases, and mental health disorders).

Clean air and sustainability necessitate a hastened transition to renewables

An absence of data for most SIDS means that most metrics for monitoring the effects of air pollution are unreliable. In congested cities, some of the main contributors to high levels of particulate matter—ie, the industrial, transportation, and commercial sectors—are also among the largest contributors to greenhouse gas emissions. There are thus clear benefits to transitioning to clean, renewable energy both to mitigate climate change and to improve air quality. Concerningly, energy generation, distribution, and transmission capacities in SIDS tend towards heavier dependence on fossil fuels. Around 17% of populations across SIDS (and 66% of the population in Guinea-Bissau) still do not have universal energy access. Increasing fair access and use of energy is fundamental to enabling development and improving the health and wellbeing of local populations. The abundance of natural renewable energy resources presents an opportunity for SIDS to transition to renewable energy, which can be locally produced and made available off-grid. Such transitions could result in substantial reductions in air pollution-related diseases and increase energy self-sufficiency. However, international cooperation and support for funding, knowledge, and technology transfer, as well as adequate commercial conditions, are necessary. Government intervention and community engagement are essential to ensure the transition towards achieving minimal or zero-carbon emissions by 2050 is hastened. Stringent policies are needed to regulate energy-intensive sectors and the international corporations that support them.

Continued destabilisation of the marine environment

There is an intimate relationship between small islands and the marine environment (the largest natural buffer for climate change), which dictates the subsistence and vulnerabilities of SIDS. Since 2015, steady increases in 3-year average sea surface temperatures, a universally acknowledged marker of the effects of global warming on ocean basins, have been noted within coastal regions around SIDS. As marine basins and coastal ecosystems are altered by climate change, there are complex implications for various aspects of wellbeing across SIDS, including food security and displacement. Contrary to global trends, marine capture of fish for production (consumption and exportation) has markedly increased in SIDS while aquaculture has declined. The increased dependence on captured fish production could have pronounced effects on the economies and coastal communities of SIDS if global warming and overfishing decline fish stocks, as has occurred in other regions. Furthermore, changes in sea surface temperatures and other ocean properties attributed to climate change have increased the exposure of populations in low-elevation coastal zones to rising sea levels and increased the potential for Vibrio transmission. Oceans absorb most of the excess heat produced by human-driven global warming, but at an immense cost to the marine environment. Without global action to substantially reduce greenhouse gas emissions by 2050, the goal of keeping global average temperature increases to less than 2°C will not be attained. SIDS and non-SIDS will continue to experience the increasing effects of the intensification of cyclonic events, storm surges, and other associated climatological processes.