11.3: The Health Effects of Climate Change
As global warming causes a cascade of climate changes and weather pattern disruptions, these too cause changes to the ecological systems in which we live, which in turn affect human health. Besides the dangers of extreme weather events, which can be deadly on their own, climate change will affect both physical and human health in many ways. According to the most recent (5th) National Climate Assessment from the U.S. Global Change Research Program:
Health risks from a changing climate include higher rates of heat-related morbidity and mortality; increases in the geographic range of some infectious diseases; greater exposure to poor air quality; increases in some adverse pregnancy outcomes; higher rates of pulmonary, neurological, and cardiovascular diseases; and worsening mental health (USGCRP, 2023b)
And these risks to health are not equal across America or across the globe. Social determinants of health also influence which populations will be at higher risk for experiencing the health effects of climate change, with the most severe impacts being felt by communities and countries with less wealth, fewer resources, less education, and those historically marginalized by the rest of society. Even within relatively wealthy countries, the populations most at risk include the elderly, unhoused, children, pregnant people, and those with chronic conditions and disabilities (USGCRP, 2023b).
While warmer temperatures in some areas actually increase the capacity to grow food, they can harm crops and farmers in other regions, and disrupt the food supply chain. The northern regions in Siberia (Russia) and Canada are now warm enough to grow crops that would not have survived before (like soy and wheat), but South Asia, South America, and Africa will experience significant losses to dietary staples (wheat, corn, etc.). Warmer weather also encourages the growth of pests, fungi, and other plant diseases, causing more crop losses (Frumkin, 2016). Warmer ocean temperatures threaten fish and shellfish, which are important sources of protein for many Indigenous communities (USGCRP, 2023b). And although CO₂ can be removed from the air by certain trees and plants, it can also change the nutrient content in some food sources like rice and soybeans. Meanwhile, weeds, allergy-producing plants (like ragweed), and poisonous plants (like poison ivy) thrive in the heat and higher CO₂ (Frumkin, 2016). Food insecurity is already high in many of the same places experiencing negative agricultural effects of climate change.
Foodborne, waterborne, and vector borne pathogens are likely to increase with climate change via several pathways. Many bacteria and fungi thrive in warm, humid climates, and many vectors (like mosquitos) breed in standing water. Water sources can be contaminated with runoff from heavy rains and flooding, and can contribute to food contamination via irrigation and washing of plants. Water shortages may also prompt people to turn to other sources of water like nearby lakes and streams, which are more likely to be contaminated with runoff and/or pathogens. And higher temperatures also promote harmful algal blooms (colonies of algae), both in freshwater (lakes) and saltwater (oceans), which can be harmful to humans and other marine organisms. Vectors like mosquitoes and ticks have spread further as other regions warm, bringing with them diseases like malaria, West Nile virus, dengue fever, and chikungunya. Even fungal diseases like Valley Fever are expected to spread north with drought conditions (Frumkin, 2016, USGCRP, 2023).
Many regions are experiencing higher-than average temperatures, and more frequent heat waves, or extreme heat events (EHE). In the summer of 2023, Phoenix experienced a record 31-day streak of temperatures over 110 ℉ (The Associated Press, 2023). While the American Southwest is not stranger to hot summers, other regions also experienced severe heat waves for which they have little history or preparation. In 2021, the Northwestern states and Canada (typically a cooler, “oceanic” climate) experienced a “heat dome” which caused high temperatures over the summer (Zhang et al., 2023). Similar heatwaves have hit Australia, China, Japan, and Europe (Zachariah et al., 2023), and can be particularly dangerous in regions that aren’t typically prepared for hot summers with air conditioning in buildings and public transportation. EHEs can cause acute heat-related illnesses (HRIs) such as heat exhaustion, dehydration, and heat stroke, and they also increase risks for cardiovascular events and kidney problems in those with chronic diseases like diabetes, as well as health complications for infants and pregnant people.
People most at risk for HRIs are older folks, young children, and pregnant people, as well as those who take certain medications, those who lack housing or air conditioning, and those who work outside. Social determinants of health also impact disparities in HRIs. If folks lack the money to pay for high electric bills, they may not run their air conditioning during the summer months. And poorer, urban communities may actually experience hotter conditions than wealthier suburban neighborhoods. A lack of tree cover/greenspace and more cement can create “urban heat islands” up to 4℉ hotter, and less likely to cool down at night. But plants that provide shade and absorb CO₂ need irrigation, which is why wealthier neighborhoods tend to have more of them (Dialesandro et al., 2021, USGCRP, 2023b). See Figure 11.3 below for region-specific climate change effects in the U.S.
Figure 11.3 Examples of Potential Health Impacts from Climate Change in the United States, by Region. U.S. Government Accountability Office from Washington, DC, United States, Public domain, via Wikimedia Commons. November 10, 2015.
Climate change affects mental health in several ways. People may lose everything in a natural disaster like a hurricane, wildfire, or flood. They may lose friends and family members, pets, photographs, homes and vehicles, and entire communities. They might lose their jobs and livelihoods to a natural disaster, or a change in climate - particularly in agricultural economies. Experiencing environmental trauma can have a severe and long-lasting impact on mental health, often causing post-traumatic stress disorder (PTSD) and heightened anxiety for many years (USGCRP, 2023). Historically minoritized communities and those who have fewer resources to begin with are often those the most harmed. For example in 2005, Hurricane Katrina devastated parts of New Orleans. The areas hardest hit were home to majority Black residents due to historical redlining practices which had segregated homeownership to certain parts of the city. These neighborhoods were below sea level, and so experienced the worst flooding (Burke & Weill, 2023). And the recovery has been just as difficult - nearly 175,000 Black New Orleans residents were displaced, and 75,000 have still not returned almost 2 decades later. Housing costs increased, flood insurance became expensive, and the federal program designed to fund rebuilding efforts ended up being sued for shortchanging poorer recipients and trying to collect overpayments (SPLC, 2023).
What happened after Hurricane Katrina is perhaps a microcosm of the displacement of communities due to climate change. Severe weather and natural disasters may destroy neighborhoods, towns, and even cities, forcing inhabitants to move elsewhere. Likewise, heatwaves and droughts may make agriculture unsustainable in certain regions, forcing people to migrate. Indigenous peoples already experience disparate impacts which threaten traditional ways of life, as well as the destruction of culturally and spiritually significant landscapes (USGCRP, 2023b). These and other socioeconomic impacts threaten civil and international conflict, and will likely disrupt global economies - all of which will have cascading effects on human health. See Fig. \(\PageIndex{2}\) below for a diagram outlining these health effects of climate change.