Extreme climatic events and human biology and health: A primer and opportunities for future research

Abstract

Extreme climatic events are increasing in frequency, leading to hotter temperatures, flooding, droughts, severe storms, and rising oceans. This special issue brings together a collection of seven articles that describe the impacts of extreme climatic events on a diverse set of human biology and health outcomes. The first two articles cover extreme temperatures extending from extreme heat to cold and changes in winter weather and the respective implications for adverse health events, human environmental limits, well-being, and human adaptability. Next, two articles cover the effects of exposures to extreme storms through an examination of hurricanes and cyclones on stress and birth outcomes. The following two articles describe the effects of extreme flooding events on livelihoods, nutrition, water and food insecurity, diarrheal and respiratory health, and stress. The last article examines the effects of drought on diet and food insecurity. Following a brief review of each extreme climatic event and articles covered in this special issue, I discuss future research opportunities–highlighting domains of climate change and specific research questions that are ripe for biological anthropologists to investigate. I close with a description of interdisciplinary methods to assess climate exposures and human biology outcomes to aid the investigation of the defining question of our time – how will climate change affect human biology and health. Climate change is a water, food, and health problem. Human biologists offer a unique perspective for a combination of theoretical, methodological, and applied reasons and thus are in prime position to contribute to this critical research agenda.

1. Introduction

The picture painted by climate change is reminiscent of an apocalyptic science fiction movie. Hotter days and heatwaves, more frequent extreme weather and rainfall, drought, rising oceans, salinization of soil and drinking water, and less food and freshwater (Pörtner et al., 2022). Each aspect of climate change carries with it distinct, yet interconnected implications for multiple aspects of human biology, health, and disease risk (Ebi et al., 2021; Jay et al., 2021; Joshua et al., 2021; Metts, 2008; Rakib et al., 2019; Raymond et al., 2020; Romanello et al., 2022; Rosinger, 2018; Rosinger & Young, 2020). For an exhaustive overview, see the 2022 Intergovernmental Panel on Climate Change (IPCC) 6^th Assessment Report (Pörtner et al., 2022).

One need only look at the cascade of historic climatic examples during the summer and fall of 2022 to witness such extreme climatic events. Multiple locations in different continents experienced the hottest temperatures ever recorded, including in Pakistan where the daytime temperature eclipsed 50° Celsius. The Western United States (U.S.) suffered extreme heat, including an infamous “heat dome” coupled with the worst drought in 1200 years (Williams et al., 2022). This drought has resulted in the Colorado River, underground aquifers, and lakes dipping to dangerously low levels, including Lake Mead which provides drinking water to 25 million people (Hannoun et al., 2022). The implications of drought reduce both water availability and remaining water quality – severely stressing socio-ecological systems and jeopardizing human health. Across the Greater Horn of Africa, in Somalia, Ethiopia, and Northern Kenya, four consecutive below average rainy seasons have brought the worst drought in 40 years resulting in the deaths of hundreds of thousands of livestock and severe famine and food insecurity and water insecurity for tens of millions (WHO, 2022). In Western Europe, a trend of extreme heat and prolonged drought (van der Wiel et al., 2022) re-emerged in August 2022, resulting in a severe heat wave and wildfires in Portugal.

Moving into late summer, several sites suffered 1000-year rainfall events. Most notably, the country of Pakistan suffered such an intense monsoon rainfall that more than two-thirds of their districts were affected. One-third of their country was flooded, which resulted in the deaths of >1500 individuals, the destruction of >1,000,000 homes, and displacement of fifty million people (Sarkar, 2022). In the US, severe flooding hit Eastern Kentucky and St. Louis, leading to death and havoc on their infrastructure, and brought national emergencies. In Jackson, Mississippi, a city that was already dealing with severe water infrastructural problems and had a boil water advisory for the prior month, flooding yielded their water systems unusable as either raw water was pushed through the pipes or no water flowed at all. A national emergency was declared due to lack of access to drinking water – including bottled water. Additionally, residents were unable to shower or flush toilets, further affecting sanitation and risk of disease. The situation in Jackson is particularly important to highlight as it was the product of a climatic and social disaster – the syndemic (or synergistic epidemic) of what happens when flooding hits a town that is 80% black dealing with structural racism and lack of investment in the water supply for a town (Nwanaji-Enwerem & Casey, 2022).

In the fall of 2022, two category 4 Hurricanes, Fiona and Ian, created catastrophic damage, hitting Puerto Rico, islands in the Caribbean, and the Southeastern United States, and in the case of Fiona reaching as far north as Canada. These severe storms served as a reminder that populations living in coastal environments suffer disproportionately to severe storms and flooding and the stress associated with the fragility of energy, water, and food services. Hurricane Fiona brought damage to places in Puerto Rico that were still recovering from a major 2017 Hurricane, Maria, that devastated power and water systems on the island (McSorley, 2022; Roque et al., 2021). Further, Hurricane Ian was the deadliest in Florida since 1935.

There is not enough space to discuss all of the extreme weather disasters that occurred in 2022. Yet all of these extreme climatic events occurred over the span of only a few months, which illustrates that the future painted by climate change is already a reality and impossible to deny. The fact that so many 1 in 1000 year events are occurring with respect to rainfall, drought, floods, and storms, tells us that perhaps we need to a recalibrate those models and projections to better match our new reality (Kent et al., 2022).

For readers interested in a deep dive on adaptation and behavioral strategies to cope with climate change, please see the 2021 special issue of American Journal of Human Biology. In that issue, evolutionary and biological anthropologists as well as archeologists discuss how biological adaptation varies from large scale adaptation measures to mitigate climate change (Anne C. Pisor & James H. Jones, 2021).

The current special issue, in contrast, aims to examine the toll that extreme climatic events have on human biology. This explicit focus on extreme climatic events can provide an understanding of what is to come under varying climate futures with respect to the impacts on health and human biology. It also broadens our understanding of the limits of human adaptability to mitigate these intense physiological and psychosocial stressors imposed by climate change. Human biologists are primed to contribute to this field owing to the breadth of theoretical insights of human adaptability, developmental origins of health and disease (DOHaD) and plasticity, biocultural analyses, and intergenerational transmission of health.

The current special issue features seven exciting papers that address five of the most important extreme climatic events posed by climate change: 1) Extreme Heat, 2) extreme cold and icing in the arctic, 3) hurricanes and cyclones, 4) historic flooding, and 5) severe drought. These articles delve into how these different extreme weather events affect dimensions of human biology, including risk of disease, food insecurity, water insecurity, stress, birth outcomes, well-being, nutrition, growth, and chronic disease. They do so by employing a variety of methods, including literature reviews, retrospective analyses with biomarkers, and longitudinal and time-series analyses. They also examine the aftereffects of these severe climatic events to provide insight into the recovery process from these events.

2. Extreme climatic events covered in this special issue

2.1. Extreme heat

Most synonymous with climate change is global warming. Earth is currently on pace to surpass the 1.5° C rise from pre-industrial levels which scientists, the United Nations (Programme, 2022), and the Intergovernmental Panel on Climate Change (IPCC) project will to lead to catastrophic changes in climate (Pörtner et al., 2022). A shifting of the global temperature to hotter temperatures not only leads to changes in vector range and impacts on infectious diseases, but it leads to greater risk of heatwaves, which are deadly, particularly to the elderly, children, and those pregnant (Jay et al., 2021). Extreme heat is dangerous to health through reduced ability to thermoregulate, increased cardiovascular load, and dehydration (Ebi et al., 2021). Extreme heat is dangerous to both humans as well as many land animals, which die during heat waves. For example, in Australia during heat waves, koalas, ring-tail possums, and birds all died due to loss of body water from active cooling and the inability to replenish that water (Turner, 2020). Ringtail possums, similar to other terrestrial animals, in Australia rely on adaptations to deal with heat like facultative hyperthermia – i.e., increasing their body temperature to maintain an elevated body temperature relative to ambient temperature. In this way, they are able to improve the efficiency of their water economy to conserve body water (Turner, 2020), similar to birds (Gerson et al., 2019). Prior work by human biologists has demonstrated the connection between ambient heat, thermoregulation, and human water needs, by examining how lifestyle and environmental changes may modify water needs, thirst perception, risk of dehydration (Bethancourt et al., 2021; Rosinger, 2015; Rosinger et al., 2022), as well as other cardiometabolic health risks like obesity (Gildner & Levy, 2021; Pontzer, 2021).

In this issue, Wolf, Vecillio, and Kenney (2023) provide an updated review of the literature to examine how extreme heat affects adverse-health events and human environmental age thresholds to extreme heat. They highlight the relations between extreme heat on morbidity and mortality, including kidney failure, heart attacks, stroke, hospital admissions, circulatory and respiratory mortality, and all-cause mortality. They demonstrate that the human limits to heat stress are lower (i.e., ~32° C) than the previously believed threshold of 35° C for wet bulb temperature. This finding has large-scale implications for human adaptability in hotter and more humid settings. They highlight the experimental procedures, including heat chambers and psychometric charts to better understand these limits (Wolf et al., 2023). Further, they discuss how global demographic patterns of an aging population will play into this dilemma, as those aged 65 and over are at greatest risk of mortality from heat stress. These findings are critical and help us understand at what ambient conditions risk from hotter temperatures and heatwaves is greatest.

2.2. Changes in extreme cold and icing

While extreme cold does not get the same attention as extreme heat in climate change research, it is important to understand how changes in historically cold regions with high snow and ice affect health and well-being of populations (Steegmann Jr., 2007). When regions that were previously frozen and hard-to-reach become warmer, an influx of people and economic exploration – often from the fossil fuel industry – can lead to ecosystem and disease risk changes (Snodgrass, 2013). Look no further than the permafrost thawing in the arctic and its potential implications for anthrax transmission and exposure to other viruses and microbes (Stella et al., 2020; Wu et al., 2022). It is the well-being and health of indigenous populations living in these regions who will be most affected. Anthropologists have previously shed light on how changes in cold weather and climate change are interlinked with changing food systems, technology, and physical activity levels, which have implications for food insecurity, metabolic health, chronic health, and birth outcomes (Egeland et al., 2011; Leonard et al., 2002; Ocobock & Niclou, 2022; Snodgrass, 2013; Snodgrass et al., 2005; Sorensen et al., 2009; Young & Mäkinen, 2010).

In this issue, Ocobock and colleagues provide a review of the impact of cold and changes in winter weather events on health and wellbeing among reindeer herders focusing on Finland as a case study for understanding changes in a rapidly changing Arctic (Ocobock et al., 2023). They focus specifically on what happens when snowfall patterns deviate from historic norms. When snowfall and ice-cover arrive later, this has implications for herders’ livelihood and behavioral strategies, which can put them at risk. In these types of ecosystems, especially where livelihood is intimately connected to the environment, it is critical to examine how changes in cold, snow, and ice affect the weight and health of reindeer themselves because this creates feedback loops to human food security and well-being. Further, changes in technology, like use of snowmobiles or all-terrain vehicles, affect exposure to wind and can increase frostbite. Ultimately, climate change will have a cascade of effects on the ecosystems and health of individuals living in these arctic environments. Clearly, more work is needed for a deeper understanding of changes in exposures and human biology outcomes in these environments.

2.3. Extreme storms: Hurricanes and Cyclones and stress

Hotter global and water temperatures lead to more frequent and more intense storm events, like hurricanes and cyclones (Pörtner et al., 2022). These severe storms are not only detrimental to immediate health through the risk of injury, death, property loss, and heightened distress (Pomer et al., 2019), but they can also have long-term negative health implications. Stress is a key mechanism for investigating the often-invisible effects of these events. Recent work by biological anthropologists have shed a light on the damaging impacts of severe storm events on body systems in model organisms. An elegant example is a recent study of Cayo Santiago monkeys in Puerto Rico who experienced Hurricane Maria in 2017. They found that the rhesus macaques who were exposed to the hurricane compared to those who were not experienced a 4% change in gene expression tied to aging-related genes and cellular aging of nearly two additional years, the equivalent of 7–8 additional human years (Watowich et al., 2022). Understanding the mechanisms linking the impact of hurricanes and cyclones in terms of stress, as well as the modifying social factors are critical to understand. This is particularly true for vulnerable groups, like pregnant women and their fetuses who are most susceptible to these stress events (Horan et al., 2022).

In the special issue, we have two papers that tackle the role of stress among pregnant women who experienced hurricanes/cyclones. The first article, by Howells and colleagues (2023) examines chronic stress during and after Hurricane Florence in Wilmington, North Carolina in 2018. They use a retrospective biomarker of chronic stress, hair cortisol concentration, to investigate stress both during and 3–4 months after the hurricane in concert with other life risk factors. They find that social support, through marriage status, is protective of heightened chronic stress both during and after the hurricane. Unmarried women may face additional compounding stressors, like lower resource support, that place them at greater risk to navigate extreme climatic events and during the aftereffects. These findings are important because they shed light on how pregnant people may experience stress and how that affects the fetus – with implications for birth outcomes

Second, Parayiwa and colleagues (2023) tackle the question of how severe storms affect birth outcomes of pregnant women who experience these shocks. They test this question using two category 5 cyclones – one in 2011 and one in 2015 – using robust quantitative methodology of interrupted time series analysis. This paper provides a nice model of how climatic data, extreme events, and hospital record data can be merged to examine the effects of severe storms. In contrast with their hypotheses, they find that early pregnancy exposure to the cyclones were associated with greater proportion of male births, potentially due to spontaneous abortion of female fetuses. The fact that they are able to examine two events provides additional strength to their findings. More work is needed to understand the impacts of hurricanes and cyclones, especially when the actual stress response of the pregnant women is measured – as the prior paper by Howells et al (2023) shows that there may be other protective factors that buffer the vulnerability to these events.

2.4. Extreme flooding

Flooding is the most common extreme-weather disaster in recent history and causes the third highest death toll after droughts and storms (World Meteorological Organization, 2021). Flooding can result from a range of other climatic events, including El Niño/la Niña oscillations, severe storms, be spurred by drought, urbanization, and anthropogenic modification of environments. All of these factors have the potential to disrupt multiple aspects of health and human biology, including water and food insecurity, risk of diarrheal and respiratory diseases, psychosocial stress, and nutrition and growth (Ahern et al., 2005; Akukwe et al., 2020; Alderman et al., 2012; Rosinger, 2018). Similar to other extreme climatic events, it is marginalized groups who disproportionately suffer the health, death, and economic effects from flooding (Alderman et al., 2012).

In the special issue, two articles discuss the effects of historic flooding events on human biology. First, Rosinger and colleagues (Rosinger et al., 2023) examine changes in measures of well-being, health, and nutrition from the end of and two months following a historic 2014 flood in the Beni, Bolivia among Tsimane’ forager horticulturalists to see how their health recovers. They find that water insecurity and food insecurity were high at the end of the flood, but that only water insecurity improved two months later. In contrast, food insecurity persisted as the flooding killed crops and resulted in loss of property and livestock. Interestingly, the loss of crops not only negatively affected dietary diversity and food availability, but it also changed hydration strategies – showing the connection between food and water insecurity. They found that blood pressure improved two months following the flood, indicating that the acute stress response to the flood dissipated as the water retreated. Nutritionally, adults and children showed divergent patterns as adults lost adiposity and children gained weight. Finally, this article demonstrates how different illnesses pose challenges at different stages of the recovery from flooding, whereby diarrheal prevalence owing to contaminated water decreased, but respiratory illnesses increased two months later.

Second, Starkweather (Starkweather et al., 2023) and colleagues examine the economic and nutritional effects of flooding using longitudinal data among a Shodagor fishing community in relation to an extreme 2017 flooding event in Bangladesh. They demonstrate that rice expenditures and fishing productivity were affected by the flood and index this to anthropometric data. They ultimately find that the flood, particularly among children and adults from households that spent more on rice – potentially as a way to mitigate against decreases in fishing income – lost more body mass, which did not recover by 2019. This finding indicates a persistent nutritional effect of flooding and provides a longer-term picture of the nutritional effects of flooding. Whereas Rosinger and colleagues (2022) found that adults lost measures of nutritional status, children at least in the market integrated community were buffered and gained measures of adiposity in the short term. What the Starkweather piece tells us is that extreme flooding events may affect nutritional status and energy reserves for multiple years – especially for populations already facing nutritional stress. Overall, these two articles indicate the multiple facets of well-being, health, and nutrition that flooding touches and how populations that are most vulnerable in the global South often bear the consequences for a prolonged period of time.

2.5. Drought and Food systems

Droughts are the final extreme weather event covered in the special issue and the most lethal as they lead to the highest death toll due to their impact on food availability. The lack of water has dangerous implications for nutrition, growth, and food security. Global climate change affects precipitation patterns, but increasing temperatures increase evapotranspiration leading to greater loss of surface freshwaters and groundwater (Pörtner et al., 2022). Human biologists have a long history of examining how populations deal with water scarcity and drought, particularly among pastoralists and how drought affects birth outcomes, nutrition, dietary strategies, and stress (Bauer & Mburu, 2017; Galvin, 1992; Leslie & Fry, 1989; Leslie & Little, 1999; Pike & Williams, 2006). Further, droughts are an interesting avenue of research in relation to gestational programming, stunting, and long-term outcomes, precisely because it is possible to tie long-term drought events to birth records (M. W. Cooper et al., 2019; Epstein et al., 2019; Hyland & Russ, 2019; Salvador et al., 2020). A DOHaD framework provides a theoretical understanding of the mechanisms driving these patterns (Gluckman & Hanson, 2004; Ross & Desai, 2005). In the short-run, however, an examination of experiences surrounding food insecurity, stress, and well-being is critical to understanding how populations navigate these challenging situations.

It is from this vantage point, that Prall and Scelza (Prall & Scelza, 2023) launch their article in this special issue. They examine how recent drought in Namibia affected diet among Himba Pastoralists, where two national emergencies were declared during the study period (2016–2019) with annual rainfall dropping by half from annual averages. They use serial cross-sectional surveys of food insecurity and dietary recall along with stressors over a four-year period. They demonstrate that the increasing drought and aridity in concert with market integration led to increases in food insecurity, especially with more frequent reports of hunger at night and not having food in the house. They further find declines in diet breadth while also seeing a shift in dietary strategies. For example, a traditional means of calories among pastoralists is milk, and they found that sour milk consumption declined – potentially due to drought impacts on livestock. While pastoralists have a long-term adaptation strategy to dealing with arid environments, they are not immune to the food and water impacts of climate change (Bethancourt et al., 2022). This article casts important light on the ramifications that prior colonial policies have on pastoralist populations in regards to access to different resources to navigate shocks, like severe drought.

3. Future research directions and methods

The topics covered in this special issue are only the tip of a fast-melting ice-berg. They provide answers but also open up new questions for study. Moving forward, there are many research opportunities available for human biologists interested in examining extreme climatic events. In the table below, I have outlined a non-exhaustive set of climate change and health questions that are well-suited to the theoretical and methodological skillsets of human biologists – some that extend from those topics covered in the articles in this special issue as well as other key topics not covered (Table 1). Also, please note that many climate domains are inextricably interconnected, whereby extreme storms lead to flooding or extreme heat leads to wildfires and drought, and thus studying one domain may necessarily extend to other domains.

Table 1:

Future research questions for human biologists to explore in relation to climate change domains

Climate domains	Examples of questions	Suggested references
Extreme heat/heatwaves	What are the human and non-human environmental limits to heat? At what limit does heat stress increase risk of cardiovascular and kidney damage?	(Pradhan et al., 2019; Wolf et al., 2023)
	How does extreme heat experienced in utero affect human water needs, thirst perception, and sweat gland distribution?	(Best et al., 2019; Rosinger, 2020)
	How does extreme heat affect cognitive processes?	(Martin et al., 2019)
	How do humans and animals conserve body water during heat stress? How does variation in morphological traits, like hair, skin, and nose shape provide protection or create potential mismatch to changing temperatures?	(Lasisi, 2021; Turner, 2020)
	How is extreme heat and humidity affecting sleep physiology and circadian health?	(Okamoto-Mizuno & Mizuno, 2012)
Extreme cold/changes in snow and ice-cover	How do extreme cold and changes in exposures to cold temperatures affect metabolism and physiology? How do exposures in utero to cold/changes in temperatures affect brown adipose tissue development?	(Leonard, 2018; Steegmann Jr., 2007) (Levy et al., 2021; Niclou & Ocobock, 2022)
	How does permafrost and economic expansion affect exposures to emerging and re-emerging diseases and cardiometabolic and chronic diseases?	(Snodgrass, 2013; Wu et al., 2022)
	How do changes in cold, snow, and ice affect mental health and well-being of indigenous populations in the arctic?	(Cunsolo Willox et al., 2015; Ocobock et al., 2023)
Extreme storms: Hurricanes/cyclones	How do extreme storms affect stress and stress physiology? What are their short- and long-term impacts on human biology? How do extreme storms affect pregnancy and birth outcomes?	(Howells, this issue; Parayiwa, this issue).
	How do extreme storms affect coping strategies, like migration, water sharing, and shifts in hydration strategies, and what are the implications for disease transmission and health?	(Anne C. Pisor & James Holland Jones, 2021; Roque et al., 2021; Stoler et al., 2021)
	How do extreme events affect mitochondrial function, methylation changes, and aging?	(Watowich et al., 2022)
Drought/water scarcity	How are drought and water scarcity affecting food systems, water and food insecurity and preferences/strategies? Can stable isotopes map changes in dietary and hydration strategies?	(Prall & Scelza, 2023; Reitsema, 2015)
	How is drought experienced in utero affecting fetal programming and stunting/birth outcomes?	(Ross & Desai, 2005)
	How does drought affect biomarkers of inflammation, immune function, methylation, and disease?	(Fujita et al., 2022; Straight et al., 2022)
Wildfires	How do wildfires affect pulmonary function? How do wildfires affect stress and cognitive performance?	(Wen & Burke, 2022)
Wildfires-heat	What are the synergistic ways extreme heat and wildfires affect water and air quality and health? What are the synergistic ways extreme heat and wildfires affect food availability, food insecurity, and water insecurity?	(Hohner et al., 2019; Kpienbaareh & Luginaah, 2019; Proctor et al., 2020)
Salinization of water sources	How does salinization of water sources and soil due to climate change affect risk of non-communicable diseases? How is it associated with birth outcomes, pre-eclampsia, hypertension, and kidney damage? How does salinization of water sources affect perceptions of drinking water sources and water insecurity?	(Gurmessa et al., 2022; Kaushal et al., 2021; Rahman et al., 2019; Rakib et al., 2019; Rosinger, Bethancourt, Swanson, et al., 2021)
Rising sea levels	How are rising sea-levels affecting health and food and water availability in coastal populations?	(Khan et al., 2011; Nunn, 2013)
Climate change	How is uncertainty about climatic extremes and climate change affecting mental health, anxiety, and depression? How is sense of loss of ecosystems affecting mental health?	(Berry et al., 2010; S. Cooper et al., 2019; Cunsolo & Ellis, 2018)

For example, while this issue covers extreme heat and cold, hurricanes/cyclones, flooding, and drought, other issues of climate change are important domains to investigate, including the impacts of wildfires and the synergistic effects of extreme heat and wildfires on air quality, water quality, respiratory health, cardiovascular health, and food and water insecurity. Globally, the number of extremely hot days has led to greater risk of wildfires (Romanello et al., 2022). Further, examining increasing salinization of water sources will be critical to studies of climate change (Kaushal et al., 2021) as they can have implications on the availability of drinking water sources and the consumption of high saline water can affect cardiovascular and kidney health (Naser et al., 2019; Rosinger, Bethancourt, Swanson, et al., 2021; Scheelbeek Pauline et al., 2017). Additionally, many human biologists work with island populations. It will be important to study how rising sea-levels are affecting their access to clean water and food and all aspects of their health and human biology. Finally, biocultural anthropologists are well-positioned to take a holistic view of the impacts of climate change on mental health, including asking how uncertainty about our climatic future is affecting hope, anxiety, and depression.

Within all of this future work, there needs to be a focus on marginalized populations. Exposures to and consequences of extreme climatic events are often the result of environmental injustice and legacies of policy which mean that the effects are felt most heavily by racially minoritized, indigenous, and lower income populations.

3.1. Methodological tools for climate-human biology research

Several interdisciplinary methods are particularly useful to link climate-related exposures to health and human biology. Here, I highlight five methods on the climatic event exposure side:

1. The use of large-scale climatic databases, like the National Climate Data Center and Climate Hazards Group InfraRed Precipitation with Station data (CHIRPS) are necessary to link ambient conditions, including rainfall, drought, and extreme cold and hot temperatures for studies of human biology. This type of data integration for long-term studies, especially during pregnancy and early childhood can help us better understand the impacts on birth outcomes and childhood nutrition (Freudenreich et al., 2022; Randell et al., 2020; Thiede & Gray, 2020; Thiede & Strube, 2020).

2. Integration and use of environmental health methods, including water quality (Wutich et al., 2020) and air quality (including particulate matter) (Awokola et al., 2020; Clements et al., 2017; Wen & Burke, 2022) will provide a way to understand changes in the water and air to which people are exposed. Systematic collection of these types of data will allow for analyses of how they are changing over time and affected by extreme events, like flooding or drought, to impact health and human biology.

3. In tracking how heat and cold stress are affecting health, being able to assess microclimate exposures will be critical. Using small, portable weather stations in field sites, like the Kestrel 5400 Heat Stress Tracker, can provide real-time changes in ambient conditions, including temperature, relative humidity, wind speed, solar radiation, heat index, and wet bulb globe temperature to link to physiological variables being measured.

4. The use of climate chambers is a more expensive, yet gold-standard measure of ensuring exposures to precise climatic conditions, including both heat and humidity as well as cold. These experimental methods are providing a way to understand human environmental limits (Vecellio et al., 2022; Wolf et al., 2023) and to test biogeographical rules in relation to different climatic conditions (Maddux, Cowgill, & Ocobock, in process).

5. Finally, the use of mapping and GIS software will help to assess differential impacts of extreme climatic events ranging from extreme flooding to hurricanes to extreme heat with respect to social disparities and environmental injustice. Mapping their spatial relation to health outcomes will demonstrate how risk differs by intersecting marginalities like low socioeconomic status and race/ethnicity (Sanders et al., 2022).

Next, on the human biology and health outcome side of the equation, a range of well-known along with novel methods can be useful to measure the effects of climate change exposures:

1. Retrospective minimally invasive biomarkers can be linked to the timing of climatic exposures. For example, several studies have used hair and nail cortisol concentration to examine chronic stress retrospectively in relation to other events (Binz et al., 2018; Horan et al., 2022; Jankovic-Rankovic et al., 2020; Rosinger, Bethancourt, Young, et al., 2021; Stalder et al., 2017). Other studies have shown how different timescales from 1 week, 3 months, and 20 months can be used to understand recent patterns of infection and immune function with C-reactive protein, immunoglobulin E, and immunoglobulin G (Urlacher et al., 2018). Both of these methods can be applied to exposures of extreme climatic events – as is demonstrated by Howells and colleagues (2023) in this issue. Regardless of biomarker, care must be made to link the measure to the timing of the exposure to the biomarker being measured.

2. Point-of-care (POC) biomarkers, including urinalysis, lipids panels, iron, glucose, and many others can provide detailed analyses on many human biology and health outcomes of interest (Madimenos et al., 2022). POC biomarkers can be useful in the field during a rapid assessment following an extreme climatic event to assess acute impacts – as is demonstrated by Rosinger et al., (2023) in this issue. These POC biomarkers have the added benefit providing the results in real-time to the studied population.

3. Integration of administrative, mortality, health-record, and birth-record data can provide large sample sizes to test ecological patterns in relation to specific climatic events (Parayiwa et al., 2022, this issue). For example, linking birth records to water quality over time can test the question of how shocks to water systems and water quality affect pregnancy outcomes, like pre-eclampsia (Thompson et al., 2022).

4. Experiential scales are important to use for understanding how lived experiences related to “too much”, “not enough”, “too dirty”, and “not the right type” of water and food are affected by extreme climatic events. Measuring water insecurity (for example with the HWISE scale)(Young et al., 2019) and food insecurity (for example with the HFIAS scale)(Coates et al., 2007) in rapid assessments following hurricanes, flooding, drought, and heatwaves will further our understanding of the full impact of these events on well-being (Rosinger, 2018; Rosinger et al., 2023).

5. The implementation of novel wearable biosensors which track physiological processes in sweat, tears, saliva, blood, and exhaled air can provide high resolution micro-level human biology and physiological data on the effects of ambient conditions (Yang & Gao, 2019; Zhang et al., 2020). For example, examining skin blood flow and fetal placental blood flow non-invasively to study how heat stress affects pregnant agricultural workers will increase our understanding of the effects of hotter temperatures (Bonell et al., 2020; Bonell et al., 2022; Chaseling et al., 2020). Integration and work with biomechanical engineers in this space will yield promising insights.

6. Finally, the use of model organisms, including non-human primates and murine models in relation to climatic event exposures can help unpack physiological and biological mechanisms and long-term implications in shorter timespans. For example, studying how extreme climatic events affect cellular damage and aging (Watowich et al., 2022).

4. Conclusion

Overall, the collection of papers in this special issue make an important contribution to our understanding of how human biology and population health are affected by extreme climatic events. A central cross-cutting theme is that these extreme climatic events affect water and food insecurity. Climate change is a water and food problem.

Human biologists offer a unique and important perspective to the study of the impacts of climate change for a combination of theoretical, methodological, and applied reasons. Expertise with evolutionary and DOHaD theory will help advance understanding of how climatic shocks affect human biology not only acutely but in the long-durée across generations. Practically, human biologists have many methodological tools needed to contribute in novel ways, including non-invasive biomarkers, survey research, interviews, and observational techniques. Implementation of additional climatic exposure methods along with methods from adjacent fields of environmental health, biomechanical engineering, and electronic medical records will further open up opportunities for addressing novel questions. Finally, human biologists work in the field with hard-to-reach and often marginalized populations, with long-term research studies. By adding environmental data collection to ongoing studies, particularly in community-engaged ways to incorporate their needs and priorities for research and action, human biologists can make unique contributions to studying the impacts of climate change.

I hope this article and special issue encourages more work by human biologists into studying and linking the impact of environment and climatic events on human biology and health. Adding to the body of evidence of the detrimental effects of climate change on human biology will hopefully further spur policy and required action to mitigate a dire climatic future.