MEVE 011: Unit 12 – Human Health
UNIT 12: HUMAN HEALTH
12.1 Introduction
Climate change is not only an environmental issue but also a major public health concern. Rising global temperatures, erratic weather events, and shifting disease patterns directly and indirectly affect human health. From heatwaves to vector-borne illnesses and food insecurity, climate change poses multifaceted threats that disproportionately impact vulnerable populations, especially in developing countries like India. Understanding these connections is essential for developing preventive healthcare systems and resilient societies.
12.2 Objectives
After reading this unit, you will be able to:
· Explain how climate change directly impacts human health through heatwaves and disease patterns.
· Describe indirect impacts such as food insecurity and malnutrition.
· Understand the effects of climate change on human settlements, migration, and livelihoods.
· Identify measures to reduce vulnerability and increase resilience to health risks caused by climate change.
12.3 Direct Impacts on Human Health
Climate change brings various immediate and measurable impacts on human health, especially through rising temperatures and changes in environmental conditions.
12.3.1 Increased Frequency of Heat Stress
One of the most visible consequences of climate change is the increase in extreme heat events. These can lead to:
· Heat stroke and dehydration
· Cardiovascular and respiratory problems, especially in the elderly and people with pre-existing conditions
· Increased mortality rates during heatwaves (e.g., Ahmedabad heatwave in 2010)
· Reduced productivity in outdoor labor sectors like agriculture and construction
12.3.2 Vector-Borne Diseases
Climate change alters the geographic distribution of vectors (such as mosquitoes and ticks), leading to the spread of diseases like:
· Malaria
· Dengue fever
· Chikungunya
· Zika virus
· Lyme disease
Warmer temperatures and prolonged rainy seasons expand breeding grounds, bringing these diseases to areas previously unaffected.
12.3.3 Non Vector-Borne Diseases
Besides infectious diseases, climate change also worsens non-communicable conditions:
· Asthma and allergies (due to poor air quality and pollen levels)
· Respiratory diseases (linked to air pollution and smog)
· Skin disorders from increased UV radiation
· Mental health disorders, such as anxiety and depression following climate-related disasters
12.4 Indirect Impacts on Human Health
Climate change indirectly affects health by disrupting food production, water availability, and social structures, which ultimately compromises nutrition and well-being.
12.4.1 Malnutrition and Hunger
Erratic weather conditions such as droughts, floods, and crop failures lead to:
· Reduced agricultural yields
· Food price inflation
· Nutrient deficiencies, especially in children and women
· Stunted growth, weakened immunity, and developmental delays
Regions that rely heavily on monsoon-dependent farming are particularly vulnerable.
12.4.2 Food Insecurity
Climate change affects both the availability and accessibility of food:
· Unpredictable climate makes farming unreliable
· Pest outbreaks and plant diseases become more common
· Water scarcity reduces irrigation capacity
· Fisheries and livestock suffer from warming oceans and heat stress
All these factors together create food insecurity, affecting millions globally.
12.5 Climate Change Impacts on Human Settlement, Migration and Livelihood
As environmental conditions deteriorate, many communities are forced to relocate or adapt, leading to complex social and economic consequences.
12.5.1 Climate Change Impacts on Human Settlement and Migration
· Rising sea levels threaten coastal cities and island nations
· Flooding and cyclones damage housing and infrastructure
· Water scarcity leads to desertification and rural decline
· Climate refugees are forced to migrate in search of safer, more livable conditions
Unplanned migration can strain urban services, increase slum populations, and intensify resource conflicts.
12.5.2 Climate Change Impacts on Livelihood
Traditional livelihoods—particularly in agriculture, fishing, and forestry—are highly climate-dependent:
· Crop failures affect farmers’ incomes
· Ocean warming affects fishing communities
· Forest degradation impacts tribal populations
As a result, people may shift to non-traditional jobs or become unemployed, increasing their vulnerability to poverty and disease.
12.6 Let Us Sum Up
Climate change has far-reaching impacts on human health—both direct and indirect. Heat stress, vector-borne diseases, and respiratory issues are becoming more common due to rising temperatures and deteriorating air quality. Meanwhile, indirect effects such as malnutrition, migration, and disrupted livelihoods are emerging as long-term public health challenges. Addressing these requires multidisciplinary approaches, including healthcare system strengthening, sustainable agriculture, urban planning, and climate-resilient infrastructure.
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UNIT 12: HUMAN HEALTH
12.1 Introduction
Climate change is emerging as one of the greatest threats to human health in the 21st century. It affects the social and environmental determinants of health — clean air, safe drinking water, sufficient food, and secure shelter. The global rise in temperature, erratic weather patterns, melting glaciers, rising sea levels, and increased frequency of extreme events such as floods, droughts, and heatwaves are all manifestations of a warming planet. These environmental shifts have both direct and indirect impacts on human health, often with the worst effects being felt by the poorest and most vulnerable communities.
Health systems worldwide are already experiencing the pressure of these climatic changes, which are resulting in the emergence and re-emergence of diseases, heat-related illnesses, mental health problems, and food and water insecurity. It is essential to understand the links between climate change and human health in order to build resilient societies and effective health policies.
12.2 Objectives
After completing this unit, you will be able to:
· Explain how climate change directly impacts human health.
· Describe indirect effects of climate change on nutrition, disease spread, and livelihood.
· Understand how climate-related migration and settlement shifts affect human well-being.
· Identify the major diseases and health conditions associated with climate change.
· Examine adaptation and mitigation strategies to minimize health impacts.
12.3 Direct Impacts on Human Health
Climate change can directly affect human health through changes in temperature and weather patterns. These changes often result in immediate health problems, especially in urban and low-resource settings.
12.3.1 Increased Frequency of Heat Stress
· Heatwaves have become more frequent, longer, and more intense in many parts of the world.
· Heat stress leads to dehydration, heat exhaustion, and even fatal heatstroke.
· Elderly people, infants, outdoor workers, and those with pre-existing health conditions are most at risk.
· Cities experience the Urban Heat Island (UHI) effect, where temperatures in urban areas are significantly higher due to concrete surfaces, lack of vegetation, and high energy consumption.
· Example: The 2015 heatwave in India resulted in over 2,000 deaths, mainly due to prolonged exposure to extreme heat.
12.3.2 Vector-Borne Diseases
· Rising temperatures and humidity levels provide favorable breeding conditions for disease-carrying vectors such as mosquitoes, ticks, and fleas.
· The geographical range of vectors is expanding, bringing diseases like:
o Malaria
o Dengue
o Zika virus
o Chikungunya
o Lyme disease
· These diseases are now spreading into areas that were previously too cold or dry for their transmission.
12.3.3 Non Vector-Borne Diseases
· Respiratory illnesses such as asthma and chronic bronchitis are worsened by rising levels of air pollution and pollen.
· Cardiovascular diseases increase due to prolonged exposure to heat and poor air quality.
· Skin cancer and cataracts may increase due to higher exposure to UV radiation.
· Mental health issues, including anxiety, depression, and post-traumatic stress disorder, are reported after climate disasters like floods, wildfires, and droughts.
12.4 Indirect Impacts on Human Health
Beyond direct exposure, climate change affects human health through disruptions in food systems, water security, and economic livelihoods. These secondary effects can cause long-term health challenges, particularly in low-income communities.
12.4.1 Malnutrition and Hunger
· Changes in rainfall patterns, temperature extremes, and increased frequency of droughts or floods lead to reduced crop yields.
· Staple crops like rice, wheat, and maize are highly sensitive to temperature.
· Food shortages lead to undernutrition, especially in children, resulting in:
o Stunted growth
o Weakened immunity
o Increased vulnerability to infections
· Pregnant women and infants are particularly at risk.
12.4.2 Food Insecurity
· Disrupted agricultural cycles result in lower food production.
· Climate-induced pest outbreaks and crop diseases reduce the availability and affordability of nutritious food.
· Livestock are affected by heat stress, reduced feed quality, and disease, leading to loss of animal protein.
· Fisheries are impacted by ocean warming, acidification, and changing migration patterns of fish species.
· All these factors contribute to chronic food insecurity, leading to long-term health issues such as anemia and vitamin deficiencies.
12.5 Climate Change Impacts on Human Settlement, Migration, and Livelihood
As climate stress increases, people are forced to relocate, adapt their living conditions, or change livelihoods. These changes cause social, economic, and health-related stress on communities.
12.5.1 Human Settlement and Migration
· Rising sea levels and coastal erosion threaten the existence of small island nations and low-lying cities.
· Flooding, desertification, and extreme weather force millions of people to migrate, either temporarily or permanently.
· These climate migrants often end up in overcrowded urban areas, slums, or refugee camps, where they face:
o Poor sanitation
o Limited access to healthcare
o Greater exposure to disease
· Loss of cultural identity, land, and community also impacts mental health and social stability.
12.5.2 Climate Change Impacts on Livelihood
· Farming communities are the most vulnerable, as they depend directly on weather conditions.
· Fisherfolk are impacted by declining fish stocks and changing aquatic ecosystems.
· Pastoralists suffer from decreased grazing land and water scarcity.
· Loss of income leads to poverty, malnutrition, and inadequate healthcare access.
· In many developing countries, women and children face the harshest consequences, as they are often responsible for gathering water, food, and fuel.
12.6 Let Us Sum Up
Climate change has emerged as a global health emergency. It affects people through direct exposure to extreme weather events and indirectly through disrupted food systems, migration, and loss of livelihoods. The most vulnerable—children, elderly, the poor, and those living in developing countries—are hit the hardest.
To address these health threats, adaptation and mitigation strategies must be implemented at all levels—local, national, and global. These include improving public health infrastructure, early warning systems, climate-resilient agriculture, food security programs, and promoting sustainable urban planning.
Ultimately, protecting human health in a warming world requires a collaborative approach involving policymakers, health professionals, environmental scientists, and communities.
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