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date: 27 June 2022

Climate Adaptation and Public Healthfree

Climate Adaptation and Public Healthfree

  • Sarah E. Scales, Sarah E. ScalesUniversity of Delaware
  • Julia MassiJulia MassiUniversity of Delaware
  •  and Jennifer A. HorneyJennifer A. HorneyUniversity of Delaware


Climate change is affecting every region of the world and is accelerating at an alarming rate. International efforts for mitigating climate change, like the Paris Agreement, through reductions in greenhouse gases are vital for slowing the global increase in temperatures. However, these mitigation measures will not have immediate impact, so urgent action is needed to address negative impacts currently posed by climate change. Adaptation measures are central to this response now, and will continue to be critical for protecting human health as temperatures rise and climate-related disasters increase in both frequency and severity. To maximize the effectiveness of adaptation measures, the health impacts of disasters should be well-characterized at the global, regional, national, and local levels. Surveillance and early warning systems are vital tools for early identification and warning of hazards and their potential impacts. Increasing global capacity to identify causes of morbidity and mortality directly and indirectly attributable to disasters are in line with the objectives of the Sustainable Development Goals and Bangkok Principles of the Sendai Framework for Disaster Risk Reduction. Both improving data collected in disaster settings and more effectively using that information in real time are central to reducing the human-health impacts of disasters. The human-health impacts of climate change and associated disasters are interrelated. Climate change and commensurate changes in environmental suitability, vector viability, and human migration strongly influence the prevalence and seasonality of infectious and communicable diseases. Both drought and flood contribute to food and water insecurity, leading to a higher prevalence of undernourishment and malnourishment, especially in children. Compromised nutritional status, in conjunction with resulting human migration, leave individuals immunocompromised and populations at a high risk for spread of infectious disease. Extreme heat exposure likewise compromises individuals’ ability to regulate their physiological response to external stressors. Disasters of all classifications can result in exposure to environmental hazards, decrease air quality, and negatively affect mental health. Accordingly, health adaptation measures to climate change must be equally interrelated, addressing needs across disciplines, at both individual and community levels, and incorporating the many facets of the health needs of affected populations.


  • Management and Planning


Climate-related disasters are increasing in both frequency and severity and have appreciable impact on human health. The Intergovernmental Panel on Climate Change (IPCC) 2021 report definitively showed that “human-induced climate change is already affecting many weather and climate extremes in every region across the globe” (IPCC, 2021). At a warming level of 1.5°C, all global regions are predicted to experience concurrent and changing patterns of climatic-impact drivers, including heat, precipitation, storms, flooding, and droughts, among other hazards (IPCC, 2021). Since the IPCC’s Fifth Assessment Report, the human causes of heat events, heavy precipitation, tropical cyclones, and droughts are even more well-established (IPCC, 2021). All of these hazards and associated disasters have severe impacts on water, sanitation, and hygiene (WASH), particularly in communities already at a high risk for hazard exposure (WaterAid, 2021a).

As communities have more climate-related hazard exposures, it is vital that these communities have the ability to adapt to threats. The IPCC Fourth Assessment Report defined adaptation as an “adjustment in natural or human systems in response to actual or expected climatic stimuli or their effects, which moderates harm or exploits beneficial opportunities” (IPCC Working Group II, 2007). Adaptation measures can include modification of the built environment, protection and augmentation of existing ecosystems, and expansion of social support programs. Such measures are often codified by accompanying laws and regulations (IPCC, 2014). To operationalize these adaptation measures from a public health perspective, it is important to identify both real-time and future hazards as well as their acute, longitudinal, and cascading health impacts.

Climate resilience necessitates collaboration between many areas of science to anticipate, prepare for, and respond to climate hazards. Distinct disciplines—economics, health, engineering, agriculture—are often siloed when creating climate adaptation policy. Such isolation greatly inhibits the potential impacts of adaptation measures. The public health impacts of climate change are multisectoral, covering a range of effects such as food and water security, compromised physical and mental health, displacement, changes in access to care, and exposure to infectious diseases. For example, WASH programs require collaboration between engineers, ecologists, public health practitioners, financiers, and urban planners, amongst others, for their effective implementation. The efficiency of climate adaptation measures can be maximized by co-opting the successes of other developmental programs and initiatives. While WASH programs are often underfunded and underutilized, these programs present opportunities for integrating climate change adaptation and policy into global development plans (Alhassan & Hadwen, 2017).

As the impacts of climate change become more evident across all facets of life, global priority setting in developing approaches to climate change mitigation and adaptation policy is slowly becoming more holistic and integrated. For example, global priorities are coordinated and reinforced across United Nations (UN) and associated agendas. The objectives set forth in the Sustainable Development Goals (SDG) are reflected in the undertakings of the United Nations Educational, Scientific and Cultural Organization (UNESCO), the United Nations Environment Programme (UNEP), the World Meteorological Organization (WMO), and the Food and Agriculture Organization of the United Nations (FAO), among others. Accordingly, adaptive measures for protecting health in the face of climate change must consider the range of influences from individual to population levels that contribute to health.

Brief History and Objectives of Global Agendas

Disasters are significant disruptors to the functioning of communities occurring at the intersection of humans, development, and natural hazards. For example, hydrological disasters, caused by changes in the presence, movement, and/or distribution of bodies of water, include floods (riverine, coastal, ice jams, flash floods) and landslides (CRED, 2020). Climatological disasters, including droughts and wildfires, are prompted by hazards arising from changing atmospheric processes across seasonal to decadal timescales. Meteorological disasters are short-lived, geographically distinct disasters caused by extreme weather and atmospheric conditions. Examples include extreme temperatures and storms. Biological disasters include epidemics and hazardous breakdowns of the human–environment interface, which create atypical human exposure to living organisms. These four categories represent the hazards most influenced by climate change.

Both climate change and disasters disproportionately affect individuals and populations experiencing greater levels of social inequality (World Bank, 2021). These groups include female-headed households, children, Indigenous persons, ethnic minorities, the nondomiciled, the elderly, persons with disabilities, sexual and gender minorities, and other marginalized groups (World Bank, 2021). Broadly, social conditions act as fundamental causes, leading to persistent and differential health outcomes (Phelan et al., 2010). Socioeconomic and social inequality contribute to increased exposure to climate hazard, higher susceptibility to loss and damage from climate hazards, and attenuated capacity to deal with those damages (Islam & Winkel, 2017). Effective undertakings for reducing the human-health impact of climate-mediated disasters must include measures to address social inequities at global, national, and local levels.

Given the wide-ranging impacts of climate change, it is nearly impossible to separate climate adaptation agendas by discipline. Rather, the historical development of initiatives to address climate change at the global level serve as guideposts to understand how the intersections of climate-related topics have changed and expanded over time. Cumulatively, the standards and objectives set forth in the UN’s Sustainable Development Goals (SDG), in conjunction with the Paris Agreement and the Sendai Framework for Disaster Risk Reduction, provide key indicators for making progress toward reducing the human-health impacts of disasters (Oxfam International, 2020). Important historical events in the development of international bodies and policies for addressing climate change and reducing the human costs of disasters are summarized in Table 1.

Mitigation broadly, and health adaptation strategies specifically, should synergistically work to reduce the situational and environmental factors that create circumstances which are detrimental to the health of the planet and its inhabitants, all while addressing the existing and emerging health and well-being needs of populations. At the core of many of these agendas is the importance of people-centered policies and careful considerations of equity and fairness; such a focus is vital for truly addressing the human-health impact of climate change and related disasters. The coordinated and complementary goals of global agendas provide common indicators to track progress toward creating better health conditions across the world. Reducing the risk of both morbidity and mortality in disaster contexts will contribute to these goals and lay the foundation for developing and instituting adaptation measures to respond to the increasing human costs of climate-mediated disasters.

Table 1. Brief Overview of Important Events Related to Climate Change and Disaster Risk Reduction Policy and Global Agendas, 1988–2021




Intergovernmental Panel on Climate Change founded through UN Environment Programme and World Meteorological Organization joint action.


The UN began giving formal, specified attention to disaster risk reduction, ushering in the “International Decade for Natural Disaster Reduction.”


First IPCC Assessment Report published, prompting the UN General Assembly to tackle climate change at an institutional level.


Yokohama Strategy for a Safer World introduced.


IPCC Second Assessment Report published.


International Strategy for Disaster Reduction introduced.


IPCC Third Assessment Report, including more in-depth exploration of human-health impacts of climate change.


Kyoto Protocol adopted.


Kyoto Protocol formally ratified.

Hyogo Framework for Action, 2005–2015, adopted, expanding on both the Yokohama Strategy for a Safer World and International Strategy for Disaster Reduction.


Global Framework for Climate Services established following World Climate Conference-3, organized by UN Educational, Scientific, and Cultural Organization; UN Environment Programme; World Meteorological Organization; Food and Agriculture Organization; and the International Council for Science.


World Health Organization and World Meteorological Organization Joint Office for Climate and Health established.


21st UN Climate Change Conference of the Parties (COP) occurred in Paris, France.

UN Office for Disaster Risk Reduction adopted the Sendai Framework for Disaster Risk Reduction, 2015–2030.


Paris Agreement, the deliverable from the 21st COP, became legally binding.

The Bangkok Principles for the Implementation of the Health Aspects of the Sendai Framework, 2015–2030 introduced.

The first Lancet Countdown annual report is published detailing the global human-health impacts of climate change in the context of progress toward Paris Agreement objectives.


24th COP takes place in Katowice, Poland, and a funding floor of $100 billion USD is pledged from developed nations to support combating climate change in developing countries.


The United States formally withdrew from the Paris Agreement.


The United States formally re-enters the Paris Agreement.

The 26th COP, widely viewed as the last opportunity for keeping the Paris Agreement objectives within reach, takes place in Glasgow, Scotland, United Kingdom.

Source: GFCS, n.d.; IPCC Secretariat, 2014; The Lancet, 2021; UNDRR, 2015, 2016; UNFCCC, 2008; United Nations, 2015; Watts et al., 2021; WHO, 2020a

Areas for Action

Early Warning Systems and Data in Disasters

As meteorological, climatological, and hydrological disasters give way to biological hazards, the development and expansion of early warning and surveillance systems is imperative to reducing the human cost of disaster sequelae. Improving data collection, quality, and access in pre-, peri-, and post-disaster contexts is critical to improve adaptation measures. For example, real-time information characterizing the human impacts of hazard exposure is needed for the timely and situation-appropriate mobilization of resources. Meteorological warning systems have been critical adaptation measures for reducing human costs of disasters. Following cyclones Lothar and Martin in December 1999 that resulted in 96 deaths in France and more than 21 billion euros in damage across the storm paths, Météo-France instituted the Vigilance warning system (CRED, 2020; Golnaraghi, 2012; Soyka, 2019). When Cyclone Klaus—the most damaging storm since Lothar and Martin—impacted France in January 2009, the Vigilance system contributed to the nearly 90% reduction in deaths (CRED, 2020; Golnaraghi, 2012). Following hundreds of thousands of deaths due to storms in the late 20th century, the government of Bangladesh and the Bangladesh Red Crescent Society developed the Cyclone Preparedness Programme that includes an early warning system (BDRCS, 2021). Expanding early warning systems to include real-time information characterizing the health impacts of hazard exposure is needed on a wider scale for timely and situation-appropriate mobilization of resources.

Data availability at a global level must also be improved to support effective adaptation moving forward. There is a notable disparity between which entities hold data, their data-sharing practices, and the accessibility of data at a global level; such barriers to data access are impediments to disaster response and limit the scope and scale at which preparedness mechanisms can be developed based on lessons learned from previous disasters. More equitable data collection and dissemination is foundational to improving the adaptive capacity of communities around the globe.

The origins of biological disasters cover a wide range of possible ways in which humans come into contact with zoonotic pathogens. The index case for the 2014 West Africa Ebola epidemic was determined to be a two-year-old in a remote village of Guinea (Baize et al., 2014). Dromedary camels have been identified as the likely host of the Middle East Respiratory Syndrome (MERS) virus, a coronavirus with limited, human-to-human transmission patterns among clearly delineated contact clusters (al Awaidy & Khamis, 2019; Hemida et al., 2014). Cyclical drought and floods in Yemen and post-cyclone flooding in Mozambique are just two examples of climate hazards preceding cholera outbreaks (Ng et al., 2020). As global water cycles have changed, deviances from historic precipitation levels have become more pronounced, and sea levels have risen. Transmission patterns of both water- and vector-borne diseases have also changed (Booth, 2018).

The late 1990s and early 2000s saw significant growth in the global capacity for the surveillance of biological hazards commensurate with increased attention for preparedness and response capacities leading up to the turn of the century. The Program for Monitoring Emerging Diseases (ProMED), started as an internet-based reporting system for clinicians, scientists, veterinarians, journalists, and the general public to access reports of infectious disease outbreaks across the globe (ProMED, 2021). This crowdsourced and expert-validated and curated reporting system was the first to report cases of high-consequence infectious and communicable disease clusters, including but not limited to Severe Acute Respiratory Syndrome (SARS), MERS, Ebola virus disease, and Zika virus. In 2000, WHO established the Global Outbreak Alert and Response Network (GOARN), which coordinates global health surveillance across 250 technical institutions and mobilizes personnel and material resources for deployment to affected countries in public health emergencies (GOARN, 2020). Public Health England, in partnership with the London School of Hygiene and Tropical Medicine, established United Kingdom Public Health Rapid Support Team (UK-PHRST) to support global epidemic responses, including in disasters (Raftery et al., 2021). However, it is imperative that surveillance systems benefit not only those with access to state-of-the-art technologies and systemic supports but also those in low-resource settings. The U.S. Centers for Disease Control and Prevention (CDC) and WHO, in collaboration with on-the-ground partners, developed the Early Warning, Alert and Response Network (EWARN). EWARN works through a system of partners across health-adjacent fields to support data collection and reporting for epidemic-prone diseases in low-resource settings and complex emergencies (Cordes et al., 2017; WHO EMRO, 2021).

Early warning systems are useful tools not only for infectious diseases. As with meteorological forecasting, early warnings for meteorological, climatological, and hydrological disasters give communities advanced, even if limited, time to prepare or begin personal response to hazards (United Nations, 2021). Warnings can be acute notifications of imminent hazards or can provide time for longer-term preparedness actions in response to impending events or continued hazard risk. For example, the CLIM-WARN project, supported by the United Nations Office for Disaster Risk Reduction and the WMO in conjunction with the Kenyan office of the United Nations Environment Programme and both international and in-country partners, sought to develop a multihazard, cross-sector early warning system tool for use in high-vulnerability settings (IKI, 2021). The project recognized that different communities have different needs, unique vulnerabilities, and varying means of communication, necessitating modifications to fit the needs of end users (Sitati, 2014). The WMO manages projects under the Climate Risk and Early Warning Systems (CREWS) Trust Fund, which supported 44 projects with more than 310 million USD in funding from country contributions and public funds (WMO, 2019). The fund works in Least Developed Countries (LDCs) and Small Island Developing States (SIDS) to provide weather and risk warnings to give governments and populations critical information for attenuating the impact of extreme weather, climatological, hydrological, and other environmental hazards (WMO, 2019).

Extreme heat early warnings are critical tools for adapting individuals’ day-to-day activities, business continuity, and transportation and energy usage for dangerous heat conditions (Hess & Ebi, 2016). Triggers for heat-health warnings are locally set, given that the thresholds for heatwaves are broadly defined as “a period of abnormally hot weather” and vary by geographic location (Masson-Delmotte et al., 2018). Although not as commonly utilized in heat early warning systems, the integration of syndromic surveillance of heat-related health issues can also contribute to both preemptive protective behaviors and early intervention to identify and address the negative health impacts of heat exposure. Undertakings like Europe’s Horizon 2020 HEAT-SHIELD are expanding the capacity of warning systems to operate as heat-health warning systems with actionable response capabilities (Casanueva et al., 2019).

Although much progress has been made in global surveillance in the last three decades, surveillance systems must continue to be augmented to adequately respond to health impacts resulting from increased hazards prompted by climate change. At a global level, disaster-related mortality is poorly characterized in terms of crude numbers and cause of death (Green et al., 2019; Saulnier et al., 2019). For example, in heatwaves, most measures of heat-related mortality are assessed through excess mortality or hospital admissions data (Limaye et al., 2018; Williams et al., 2018). Better methods for characterizing the “near misses”—negative health impacts that do not result in clinical care—as well as morbidity and mortality in affected communities are critical for developing and operationalizing more effective measures for adapting to extreme heat events. Another indicator of the SDGs is increasing the number of countries with vital registration systems to ensure that cause of death is recorded. As natural hazards affect more populations globally, understanding the impacts in terms of mortality will be vital for creating meaningful adaptation measures. Cause of death identification provides important information for public health preparedness and response to disasters. For example, cause of death data can be incorporated into forecasting and surveillance systems, increasing sensitivity for detecting early warning signs of clusters of disease, effectively triggering alerts for appropriate health interventions to break disease transmission patterns, institute mitigation strategies, or bolster service provision to vulnerable communities to prevent future deaths.

Floods and Droughts


Changes in precipitation patterns are predicted with medium to high confidence across global regions under a warming level of 1.5°C (IPCC, 2021), making it clear that climatic changes are outpacing the potential impact of climate mitigation strategies. In July 2021, the same week the European Commission formally adopted its 2030 Climate Target Plan, more than 170 people in Western Europe were killed in floods while thousands more were evacuated as rivers continued to rise following record rainfall (European Commission, 2021; Wischgoll & Sahl, 2021). Displacement, sanitation, potable water and food security, pathogen and environmental exposures, and vital infrastructure are among the most pressing concerns following flood events across countries of all economic development levels (Barrett et al., 2015). Globally, about 785 million people do not have ready access to potable water, and the associated risks are augmented in post-flood events (WaterAid, 2021a). Adaptation measures for protecting human health must address the full spectrum of health risks posed by flood exposures.

A modeling study under an assumption of stable emissions at 750 ppm carbon dioxide in the year 2210, as well as constant numbers of annual cases and stable costs per treatment, estimated the annual cost of treating malaria, malnutrition, and diarrheal diseases will be in the range of 4 to 12 billion USD by 2030 (Ebi, 2008). Flooding and unusually wet seasons contribute to higher incidence rates of malaria in affected areas, leading to higher numbers of disability-adjusted life years in those populations (Ding et al., 2014). Floods and post-flood environmental exposures also increase the incidence rates of diarrheal diseases such as bacillary dysentery, cholera, Cryptosporidium hominis, E. coli, Campylobacter, and other enteric pathogens (Brumfield et al., 2021; Dimitrova & Kumar Bora, 2019; Gertler et al., 2015; Ma et al., 2021; Rieckmann et al., 2018; Yard et al., 2014). Malaria and diarrheal diseases, often comorbid with undernutrition and malnutrition, are leading causes of childhood deaths globally (WHO, 2020b). Public health measures will be central to reducing the burden of early childhood diseases and associated mortality as more children are exposed to hydrological disasters globally. Early nutritional interventions are critical for reducing the susceptibility of young children to infectious disease and bolstering immunological capacity to respond to pathogen exposures associated with flooding (Chandra, 2002).

In a study assessing the vulnerability of Vietnamese provinces in the Mekong Delta, an area considered to be highly vulnerable to extreme climatic events and hydrological disasters, the level of health vulnerability and exposure to heavy flooding were highly correlated (Phung et al., 2016). Provinces with higher population density, unemployment rates, levels of population migration, malnutrition, infant mortality rates, and proportions of women, children, and elderly were more susceptible to negative health impacts in flood events (Phung et al., 2016). In India, a country with an undernutrition prevalence of 15.3% between 2018 and 2020, children are at an appreciably higher risk of undernourishment when they experience wetter-than-usual monsoon seasons and associated floods (Dimitrova & Kumar Bora, 2019; Muttarak & Dimitrova, 2019). Addressing the underlying prevalence of childhood undernutrition and malnutrition, in line with objectives set forth in the SDGs, is vital for longitudinally decreasing the susceptibility of populations to negative health impacts of disasters.

In March and April 2019, successive cyclones Idai and Kenneth made landfall in Beira City and Cabo Delgado, Mozambique (Cambaza et al., 2019). The cyclones and the associated flooding and rainfall affected roughly 1.85 million people, not including affected communities in the neighboring countries of Zimbabwe and Malawi (UNICEF, 2019). Following Cyclone Idai, a cholera epidemic was declared in March 2019, and a second outbreak was declared in May 2019 following the flooding and mass displacement from Cyclone Kenneth (Cambaza et al., 2019, 2020). Cholera control is a priority of the SDGs, with the Global Task Force on Cholera Control setting objectives by 2030 for a 90% reduction in global cholera deaths and the elimination of cholera from a minimum of 20 countries (GTFCC, 2017; Legros, 2018). Early warning and surveillance systems are paramount to detecting and controlling outbreaks of cholera, as reflected in the Sendai Framework’s call for the development and utilization of multi-hazard early warning systems to reduce disaster risk. Cholera is endemic in Mozambique, occurring in seasonal, weather-mediated cycles. Using the knowledge of the seasonality of cholera, the National Meteorology Institute’s storm tracking models were used to give advanced warning to communities and response workers in areas expected to see high levels of flooding, rainfall, and damage to critical infrastructure and likely cholera outbreaks (Cambaza et al., 2019; Kahn et al., 2019).

Accordingly, shelters for those displaced by the cyclones and subsequent floods were set up with logistical measures for cholera control in place. Such measures included, but were not limited to, the allocation of basic dignity kits, Certeza chlorine tablets for distribution at water points-of-access, and WASH campaigns (Chen & Azman, 2019; Lequechane et al., 2020). While these measures are critical for curbing cholera transmission in crowded, often unsanitary camp conditions, the rurality of most affected areas posed additional complications to its effective control. In addition to meteorological predictive modeling, additional modeling efforts were undertaken to plan and operationalize local, provincial, national, and international efforts to support a mass vaccination campaign and set up an operational contact tracing and surveillance system. Utilizing Gavi’s global oral cholera vaccine (OCV) stockpile, mass vaccination with whole-cell OCV (Shanchol and Euvichol+) was targeted to high-incidence areas (WHO, 2019). Ensuring the integrity of global vaccine stores and addressing equitability of access to vaccines are imperative for mounting effective adaptive responses. Preparedness and response capacity can be enhanced by the utilization of predictive modeling and quickly operationalized surveillance systems. While these are critical tools for reducing the human-health impact of disasters, such methods are not fail-safe and do not preclude the potential for hazards to place a heavy burden on affected populations.

Measures for protecting human health should be incorporated into flood adaptation plans. While the imperative of providing safe drinking water and quickly re-establishing the integrity of water and sanitation systems is well-acknowledged, the execution of these measures is typically slow and managed on a very local scale. As floods affect larger and larger geographic areas for longer periods of time, support needs to be extended across jurisdictional levels to ensure that even smaller, lower-resourced communities have the capacity to respond to the immediate health needs of their populations and the surge capacity to maintain response as long as is necessary for protecting health. Environmental sampling and immediate activation of surveillance systems should be carried out to adequately prepare populations for potential flood-related infectious disease outbreaks. Further, shelters and temporary units for displaced persons should be prepared to logistically handle communicable diseases—from COVID-19 to cholera—in these communal settings.

Health system resilience and medical surge capacity are other critical considerations for assessing population risk and vulnerability (Runkle et al., 2018). Provision of care and protection of healthcare infrastructure, particularly in high-propensity flood areas, are also cornerstones of climate change adaptation and health in the context of floods. Flood-related disruptions to water, power, supply chains for medical material, and transportation infrastructure have substantial impacts on healthcare facilities’ ability to provide care and continue serving communities (HCWH, 2018). Further, health threats—both physical and mental—related to flooding do not end when flood waters recede, placing continued stress on healthcare systems (Ahern et al., 2005; Ahmad et al., 2011; Bubeck et al., 2018).

Challenges related to health system resilience and response capacity are faced in both well-developed healthcare systems and more fragile systems. In the United Kingdom, a series of qualitative interviews with healthcare providers in communities susceptible to coastal flooding found that the healthcare sector, at large, does not have the requisite capacity to respond to existing meteorological hazards and will be further overwhelmed as they become more frequent and severe (Landeg et al., 2019). Hurricanes Katrina (2005), Sandy (2012), and Harvey (2017) overwhelmed hospitals and healthcare facilities in three large U.S. cities, often with patients who lacked access to medicines and durable medical equipment needed for the maintenance of chronic conditions including diabetes and cardiovascular diseases (Sen et al., 2018). Following a 2008 flood in rural communities in Orissa, India, primary and preventive care health services were severely impacted. A review of the factors that contributed to experienced challenges highlighted the need for facility-specific preparedness and operations continuity plans (Phalkey et al., 2012). Ensuring standardization of normal operations and instituting disaster contingency plans are important steps for bolstering local adaptation plans.


Climate change, while impacting the entirety of the world’s population, leaves the most physically and socially vulnerable populations at the highest risk of exposure and negative outcomes related to changing climate hazards (Acharya, 2015; Levy & Patz, 2015). The Sahel region of the African continent and the Horn of Africa face high levels of food insecurity, driven by paradoxically complementary floods and droughts, as well as conflict and migration (FAO, 2014, 2021; Lindvall et al., 2020; Mayans, 2020). In 2020, roughly 5.5 million people in South Sudan were estimated to experience food insecurity resulting from the long-term impacts of a 2017 famine, driven in part by flood and drought conditions (WFP, 2019). In 2020 alone, more than one million Somalians were displaced by floods, drought, and conflict (NRC, 2021). From January to March 2021 alone, roughly 38,000 people were displaced by drought. In Yemen, water insecurity and conflict simultaneously exacerbate one another, contributing to one of the most profound humanitarian crises in history (Suliman, 2019). By the end of 2021, United Nations Children’s Fund (UNICEF) predicted 2.3 million children under the age of five would be experiencing acute malnutrition (UNICEF, 2021). These estimates are reflected in the 2.2 million children and 1.3 million pregnant and lactating women and girls projected to suffer from acute malnutrition through 2022 (WFP, 2022). The impacts of droughts are far-reaching and complex, and the sheer number of individuals living with perpetual exposure to associated food insecurity, displacement, and conflict necessitate immediate action. The needs of affected populations far outpace the potential impacts of mitigation measures such as reducing greenhouse gas (GHG) emissions, again highlighting the urgent need for comprehensive health adaptation measures (Lelieveld et al., 2019).

Adaptation objectives for protecting human health in drought conditions are centered on food security due to the cascading negative impacts (e.g., immune deficiency) of undernutrition and malnutrition, especially for young children (Rytter et al., 2014). The timely provision of macronutrient balanced food aid and micronutrient supplementation is central to adaptation in food insecure populations (Bhatia & Thorne-Lyman, 2003). Acutely malnourished children are roughly nine times more likely to die of diarrheal disease and early childhood diseases such as measles than their healthy counterparts (UNICEF, 2018). Given the severe impacts of malnutrition on immune system function and the high proportion of deaths attributable to diarrheal disease, malnutrition, and early-childhood vaccine preventable diseases (VPD), additional public health undertakings such as supplementary immunization activities (SIA), expanded programs on immunization (EPI), and vitamin A supplementation should also be included in the adaptation (Cabrol, 2011; Prendergast, 2015). Further, it is not feasible or reasonable to separate climate change from geopolitical considerations, including sustained civil and international conflict. Accordingly, the challenges of mobilizing humanitarian responses in areas experiencing conflict must be considered in the logistical requirements of adaptation plans. Understanding the population-level impacts of conflict and the associated displacement is critical for the allocation of food, water, and medical countermeasures in complex emergencies (Anderson et al., 2021).

Biological Hazards

Climate change and resulting disasters have greatly influenced the seasonality of diseases and vector patterns (Rocklöv & Dubrow, 2020). By 2050, more than 1.8 million people will be at risk of malaria, not accounting for the potential mitigative effects of the RTS,S/AS01 malaria vaccine recommended for widespread use by WHO in October 2021 (Onyango et al., 2016; WHO, 2021). A spike in malaria cases and a measles outbreak were associated with disruptions caused by cyclones Kenneth and Idai (Mongo et al., 2020; Schroeder, 2019). Conversely, following an El Niño event in Tanzania in the 1997/1998 cycle, the incidence rate of malaria dropped notably (Lindsay et al., 2000). Cyclone Amphan impacted the Indian state of West Bengal, requiring mass evacuations across a region of more than 9 million residents, interrupting testing capacity, and leading to a spike of the case fatality rate for COVID-19 (Baidya et al., 2020). Tuberculosis, typhoid, West Nile virus, yellow fever, African sleeping sickness, and bacterial pneumonia are diseases with transmission and infection patterns driven by vector seasonality and seasonal climate (Martinez, 2018).

Transmission of both vector-borne and communicable diseases is greatly influenced by human behaviors, including behaviors prompted by climate change (Verelst et al., 2016). Measles transmission, for example, is influenced by rural-urban migration patterns mediated by agricultural patterns due to extended droughts and unusually heavy wet seasons (Ferrari et al., 2008, 2010). By altering the number of contacts, the amplitude of outbreaks of human-to-human transmission is commensurately altered (Ferrari et al., 2010; Korevaar et al., 2020). Redoubled efforts to increase global vaccination coverage will continue to be an important aspect of decreasing the human cost of disasters in the era of rapid climate change. Disruptions of routine immunization schedules and vaccination campaigns globally due to limitations related to public health workforce shortages, fear of infection, and logistical challenges related to vaccine supply mean that after the COVID-19 pandemic many large gaps in vaccine coverage will need to be addressed (Olorunsaiye et al., 2020).

Damages to municipal services such as garbage, waste, and water management due to flooding and extreme weather events can increase infectious disease risk in post-disaster settings. In Lewes, England, the risk of gastroenteritis among adults exposed to flooding was 70% higher than adults not exposed to flooding when controlling for age and sex (Reacher et al., 2004). Beyond the immediacy of exposure to enteric pathogens in flood and storm waters, WASH considerations are also important for other infectious diseases such as cutaneous leishmaniasis (Hussein et al., 2019). Secure water storage and distribution of potable water is needed for vector-control in drought-affected populations, as shown by the emergence of chikungunya in coastal East Africa starting in 2004 (Chretien et al., 2007). Following Hurricane Katrina, the incidence rate of West Nile neuroinvasive disease was 282% and 193% higher in affected areas of Mississippi and Louisiana respectively than in unaffected areas (Caillouët et al., 2008). Because arbovirus-carrying mosquitoes breed in wet environments, standing water from significant coastal flooding and rainfall, in addition to increased exposure of individuals to these flooded areas, likely contributed to the observed increase in West Nile incidence. Further, because disasters do not occur in a vacuum, the impacts of climate change augment the negative effects of non-climate related disasters, as seen in the increased vector density and disease burden of Zika in Ecuador following an earthquake in April 2016 (Reina Ortiz et al., 2017).

As historically cooler areas become warmer, pathogens and vectors that were once unable to survive in those environments are now able to thrive there. Further, globalization of trade and travel has created more complex pathways through which vectors can be introduced to geographically new areas. For example, tick-borne encephalitis and Lyme disease, transmitted by Ixodes ricinus, are emerging diseases of concern across Europe (Baylis, 2017). Zika virus, an arbovirus carried by Aedes aegypti mosquitos, infected over 1 million people in across the Americas in 2015–2016, with likely transmission beginning years before coming to prominence (Baylis, 2017; Lowe et al., 2018). Other competent vectors for Zika transmission, as well as dengue, chikungunya, and leishmaniasis, have extended their geographic distribution and are present in much of Europe and in the Southern United States, resulting in cases of these diseases from Italy and France to Russia and Georgia (country) to Texas and Florida (Akiner et al., 2016; Baylis, 2017; Wright et al., 2008).

Extreme Heat

It is “virtually certain” that heatwaves will continue to increase in frequency and intensity moving further into the 21st century (IPCC, 2021). The human-health impact of heat is indisputable, with exposures resulting in immediate negative health impacts (Guo et al., 2014). Heat stress, dehydration, and rapid changes in body heat deteriorate an individual’s ability to regulate their body temperature, potentially resulting in cramps, exhaustion, heatstroke, and hyperthermia (WHO, 2018). Heat can also compromise the safety of publicly accessible water sources, encouraging the proliferation of bacteria and water-borne pathogens if not treated and safely stored (Chalchisa et al., 2017). Migrant and seasonal workers are at a high risk of occupational exposure to extreme heat, and high morbidity and mortality rates are observed in these populations during periods of extreme heat (Pradhan et al., 2019; Zhang et al., 2016). Generating awareness for physiological symptoms of heat-related conditions, expanding surveillance and reporting requirements for heat-related conditions, ensuring community access to safe drinking water, and changing or limiting work hours during heatwaves are straightforward yet high-impact adaptation measures.

Local measures for heat protection are among the most relevant and effective for protecting population health. Adaptation at the community-level such as the implementation of a heat action plan has been successful in reducing heat deaths in Ahmedabad, Gujarat, India (Ahmedabad Municipal Corporation, 2016, 2019). In 2015, a historic heatwave affected much of India and Pakistan. While 2,300 Indians died due to heat-related causes, fewer than 20 heat-related deaths were recorded in Ahmedabad, a city of roughly 8 million people, despite experiencing temperatures exceeding 45°C (Ahmedabad Municipal Corporation, 2016). This has been widely attributed to the clarity, completeness, and operational capacity of Ahmedabad’s heat action plan. Other cities have effectively implemented heat action plans. More than 1,000 people were killed in the same 2015 heatwave in Karachi, Pakistan, prompting more deliberate mobilization of community networks and collaboration between disaster management, public health, education, meteorology, and social services professionals to be integrated into the city’s heat action plan (Commissioner Karachi, 2017; Ghumman & Horney, 2016). Queensland, Australia’s heat action plan not only addresses the clear health implications of extreme heat exposure but also addresses the non-clinical impacts of extreme heat, such as increased demands for water (Queensland Government, 2019). Clear guidance is provided for individuals, community groups, and local governmental entities to manage the increased demand for water, potential impacts on food systems, and shortcomings in infrastructural capacity to manage additional stress. Clearly articulated, coordinated, and locally administered adaptation methods such as these should become standard practices for all municipalities to ensure community-level preparedness for and protection during extreme heat events.

Extreme heat events pose unique threats to water security and safety. Across the world, women and girls spend more than a collective 200 million hours per day traveling to collect and transporting water (UN Water, 2021a; WaterAid, 2021b). Such physically demanding tasks in extreme heat conditions contribute to heat-related morbidities such as heat exhaustion, dehydration, and exacerbation of preexisting conditions. Recognizing the importance of safe and readily available access to water, SDG 6 focuses on improving “water and sanitation for all” (UN Water, 2021b). Water storage, especially in extreme heat events, has ramifications for human health. Within hours of extreme temperature onset, water stored in galvanized drums and/or metal tanks can exceed acceptable temperature limits for human use and can provide ideal environments for the proliferation of microbes (Chalchisa et al., 2017). Temperature changes also impact natural reservoirs for waterborne pathogens like Vibrio cholerae; these effects can be both positive and negative with some pathogens thriving in warmer waters while others find extreme temperatures and temperature fluctuations to be detrimental (Jones et al., 2020).

As populations become urbanized, the urban heat island effect should be addressed through innovative design, the expansion of urban green spaces, and investing in more efficient transportation and energy infrastructure. The heat management plans of Adelaide, Australia; Barcelona, Spain; Santiago, Chile; and Los Angeles, United States have explicitly incorporated urban design initiatives into adaptation measures (Paz et al., 2016). Such design measures include greening cities and reducing the impacts of the urban heat island effect through green infrastructure and energy use changes (Newman et al., 2019). Green spaces—parks, orchards, grassy areas, sports fields—offer health benefits beyond helping dissipate urban heat. Green spaces provide mental health benefits to communities, improve air quality, and, in some cases, offer safe recreational spaces for communities (Adulkongkaew et al., 2020; Ramirez-Rubio et al., 2019). Other design measures include the use of thermal resistant building materials, reflective paints, and engineered airflow (Kuta, 2021; Vellingiri et al., 2020). Such measures are particularly important in low-income and informal settlement housing for improving ventilation and reducing ambient indoor temperatures (Santamouris et al., 2007). Adaptation to extreme heat should include innovative bioclimatic approaches to improving built environments.

Mental Health

A range of psychological and mental health issues—post-traumatic stress disorder (PTSD), depression, generalized anxiety disorder (GAD), prolonged grief disorder—are clearly associated with disaster exposure (Goldmann & Galea, 2014). Direct and indirect impacts of climate change influence mental health experiences and inform the steps needed for mental health protection across policy, practice, and research domains (Berry et al., 2010; Hrabok et al., 2020; Palinkas & Wong, 2020).

In August 2005, Hurricane Katrina made landfall in southeast Louisiana, United States as a Category 3 hurricane before making a second landfall, again as a Category 3 storm, in Hancock County, Mississippi (National Weather Service, 2016). Katrina generated the highest storm surge in U.S. history, peaking at 27.8 feet in Pass Christian, Mississippi (Knabb et al., 2005). The scale of the disaster had severe and far-reaching population-level impacts. Comparing mental health as captured in the Behavioral Risk Factor Surveillance System surveys, the number of poor mental health days experienced by adult Mississippians and Louisianians comparatively increased between 2004 to 2006 following Hurricane Katrina in 2005 (An et al., 2019). Wildfires have both acute and chronic impacts on mental health, including increases in substance use and dependence (To et al., 2021). Following the 2018 Camp Fire in California, anxiety disorder, post-traumatic stress disorder, and depression exceeded pre-disaster levels (Silveira et al., 2021). Access to treatment may also be limited as disasters can isolate victims from support networks and reduce access to community-based supports and resources.

Among children, research is beginning to look at the synergistic effects of physical security, physical health, and mental health in disaster contexts, but more work is needed to understand the pathways through which these modulate physical, behavioral and developmental, and mental health outcomes (Felix et al., 2020). Nearly half of middle and high school students surveyed in Alberta, Canada after the 2016 Fort McMurray wildfire had one or more probable diagnoses of PTSD, depression, GAD, or substance use (Brown et al., 2019). Students with higher impact exposures were more likely to report negative mental health effects compared to their peers. Children and youth with disabilities not only face the mental health effects of hazard exposure but also the stressors related to navigating limited accessibility, disruption of schedules and educational support programs, and compromised social and familial support systems (Ducy & Stough, 2021; Ronoh et al., 2015). The COVID-19 pandemic has had severe mental health impacts globally, resulting from both direct effects of illness and more distal factors. Lockdowns and loss of social connectivity, politicization of response, stigma of disease, media saturation, job losses, changes to work environment, school closures, lack of access to personal protective equipment, and a range of other considerations have contributed to the negative mental health impacts of the COVID-19 pandemic (Brooks et al., 2020; Kumar & Nayar, 2021; Pfefferbaum & North, 2020; The Lancet Psychiatry, 2021).

Displaced populations, even those temporarily displaced, face unique stressors that require immediate, in-shelter support and access to care as well as longitudinal support for reintegration into social support systems when either returning or moving to new communities. Following Hurricanes Sandy and Harvey, which impacted the U.S. mid-Atlantic states and Texas respectively, displaced persons isolated from community resources experienced high levels of mental distress across recovery time periods that generally exceeded the limited availability of post-disaster mental health supports (Taioli et al., 2018). As climate migration becomes even more prevalent, the mental health impact of this displacement will become more important (Balsari et al., 2020; Lustgarten, 2020). Central to adaptation, immigration policies must recognize and accommodate displaced individuals, and appropriate social and mental health services should be accessible to persons both peri- and post-migration to attenuate the psychological impacts of climate-driven displacement.

Further characterizing these needs is imperative for curbing the negative impacts of disaster exposure. Climate adaptation moving forward should include comprehensive mental health and psychosocial support systems to address both the acute and long-term mental health impacts of hazard exposure. More and more individuals will experience disasters, often multiple disasters throughout their lifetimes. Climate grief and solastalgia, or the sense of loss and anxiety related to the changing environment and its impacts on day-to-day life, should also be considered in adaptation policy addressing mental health (Albrecht et al., 2007; Bourque & Willox, 2014; Pihkala, 2020). Characterization of dynamic, climate-related mental health support needs must be a focus of future research. Better characterization of the mental health impact of disasters can provide individuals, response entities, and communities with the information needed to make informed decisions for protecting long-term mental well-being as climate change accelerates.

Environmental Exposures, Pollution, and Hazardous Materials

Hurricane Katrina increased the exposure to hazardous materials throughout the Gulf region, exposing survivors and responders to pollutants such as oil, lead, formaldehyde, and particulate matter (Rabito et al., 2012; Wilson et al., 2020). Following flooding resulting from Hurricane Harvey, recreational areas in Harris County, Texas, were susceptible to petrochemical exposure via flood-associated breaches at Superfund sites, petroleum storage tanks, and municipal solid waste sites and potential redistribution of contaminated soils and sediments (Karaye et al., 2019).

Studies related to air pollution and climate change typically assess impacts in terms of observed and expected mortality and place less focus on assessing changes in morbidity patterns (Orru et al., 2017). The relationship between climate change and air pollution is complex, necessitating coordination from experts in both domains to ensure that policy decisions work toward curbing the negative effects of both (Kinney, 2018). Understanding the interdependence of air pollution and climate change is difficult in that diligent efforts to reduce emissions as laid out in the Paris Agreement would, in general theory, also improve air quality and decrease the negative health impacts of exposure to increased concentrations of pollution (Orru et al., 2017). Various climatic events such as extreme heat and wildfires increase air pollution concentrations. Extended exposure to poor air quality can exacerbate preexisting cardiovascular, pulmonary, and metabolic conditions, increase the risk for infectious diseases like COVID-19, and be harmful to small children, pregnant persons, and the elderly (Anenberg et al., 2020; Cascio, 2018).

The majority share of adaptation measures that address environmental exposures due to climate change and/or disaster exposure must be facilitated at a policy level rather than through individual behaviors. For example, a 2019 study from the U.S. Government Accountability Office found that roughly 60% of Superfund sites in the United States could be affected by flooding, storm surge, wildfires, or sea-level rise in the immediate future (GAO, 2019). Water and environmental management will play a central role in navigating the risks at the intersection of built environment and climate-driven natural hazards. Tighter regulations and stronger containment protocols for hazardous materials sites are needed to protect communities from the compound effects of disaster and hazardous material exposure.


Climate change is accelerating, and the health impacts of climate change will become even more acutely felt across the globe. Even if goals for reductions in the levels of GHG emissions are met and countries and blocs move toward the goal of carbon neutrality, the damage caused by climate change will outpace and outlast the effects of the steps taken to mitigate further damage. While mitigation strategies are central to international priority-setting frameworks like the Paris Agreement, adaptation measures serve as the stopgap to address the existing and imminent threats posed by a changing climate.

Meteorological, hydrological, and climatological disasters, as well as biological disasters, represent the hazards most affected by climate change. Risk of hazard exposure and vulnerability to resulting disasters are often interrelated, creating compound and complex emergencies that necessitate coordinated responses to reduce the human-health impact of disaster exposure. The need for such coordination is realized in the complementary goals of global agendas such as the 2015–2030 initiatives set forth by the UNDRR, WMO, FAO, and UNEP, among others. Redoubled efforts to ensure collective progress toward common goals and continued dialogue to iteratively update the emerging needs addressed in common goals will facilitate even greater impact.

Better understanding of both the acute and chronic impacts of disaster exposure on mental and behavioral health is essential to protecting overall human health as disaster exposures become even more ubiquitous. Food and water insecurity are at the heart of virtually all peri- and post-disaster needs of affected populations. WASH programs are existing, critical resources from which to build climate change adaptation measures. Further, adaptation measures should include plans for food and potable water provisions on massive scales, along with complementary public health measures such as mass vaccination campaigns and logistical management of disease risk. Plans for accommodating increasing numbers of climate refugees and displaced persons are essential for all health adaptation, including but not limited to providing physical and mental health resources in temporary shelters and instituting legal protections. Cross-cutting, innovative approaches to address the totality of the human-health impact of disasters will drive the success of health adaptation to climate change.

Positive strides have been taken in some areas to build global capacity for protecting health in disaster settings. However, existing systems, preparedness and response capacities, and evaluation tools must scale up to meet the level of need driven by the increasing frequency and severity of climate-related disasters. Data collection and sharing systems in disasters—from surveillance and early warning systems to vital statistics—are, in their present state, inadequate for capturing the full spectrum of human-health costs or the benefits of adaptation. Bolstering and expanding these systems will give policymakers the tools they need to develop timely, evidence-based adaptation measures.

Further Reading