Heat Stress, Health, and One Health Concerns: A Scientific and Philosophical Exploration
Dr. Simant Kumar Nanda, Bhubaneswar, Odisha
Introduction
Heat is not just a climatic variable but a profound determinant of human, animal, plant, and ecological health. The last decade has been the warmest on record, with the World Meteorological Organization (WMO) confirming 2023 as one of the hottest years in global history (1). Rising temperatures are now linked with recurring heat waves, reduced productivity, increasing disease burden, and ecological imbalance. South Asia, particularly India, is at the frontline of this crisis, with average temperatures steadily exceeding long-term norms.
The problem of heat stress requires a One Health perspective, recognizing that human well-being, animal welfare, crop productivity, and environmental balance are inseparably linked. Indian philosophical traditions also remind us that survival during extremes depends not just on technology but also on moderation, ecological harmony, and collective responsibility.
Heat Stress and Human Health
When environmental temperature exceeds human thermoregulatory capacity, the body faces dehydration, electrolyte imbalance, heat exhaustion, and potentially fatal heat stroke. Humans maintain a narrow internal temperature range (36.5–37.5 °C), and exposure to sustained high temperatures disrupts this balance. The National Disaster Management Authority (NDMA) reported that more than 6,000 Indians died of heat waves between 2010 and 2020 (2).
Heat stress also reduces labor productivity, especially in outdoor workers. The International Labour Organization (ILO) estimates that by 2030, South Asia will lose up to 5% of total working hours due to heat, equivalent to 34 million full-time jobs (3). Agricultural workers in Odisha, construction workers in Delhi, and traffic police in Chennai are already unable to sustain outdoor activity during peak summer.
Heat worsens chronic illnesses and reduces cognitive capacity. Renal strain from dehydration contributes to chronic kidney disease of unknown origin (CKDu), particularly in agricultural workers in Andhra Pradesh and Sri Lanka (4). Neurological studies show that decision-making, memory, and learning are impaired under high-temperature exposure (5). Thus, both physical and intellectual human capital are threatened.
Impact of Heat Stress on Animals and Birds
Livestock and poultry, vital for food security, are highly vulnerable to heat stress due to limited thermoregulation. Dairy cattle experience decreased feed intake, reduced milk yield, and reproductive failures. The Indian Council of Agricultural Research (ICAR) estimates milk production losses of 15–20% during severe heat waves, amounting to thousands of crores in economic losses (6).
Poultry shows even greater sensitivity to heat stress, leading to higher mortality. Broiler farms in Andhra Pradesh and Telangana report summer mortality rates of 8–10%, compared to 3–4% in cooler months (7). Egg production also declines, and heat-induced immunosuppression increases disease outbreaks like coccidiosis.
Wild birds face mass mortality during extreme summers. In Rajasthan and Gujarat, pigeons, crows, and migratory birds have been found dead in hundreds due to dehydration and heat stroke (8). This indicates how rising temperatures disrupt biodiversity and ecological resilience.
Heat Stress and Crop Productivity
Plants, being immobile, suffer directly from elevated temperatures that damage photosynthesis, flowering, and grain formation. For wheat, India’s second most important cereal, yields decline by 3–5% for every 1 °C rise above the optimum (9). In Punjab and Haryana, premature grain filling due to heat reduces both quality and quantity.
Rice and maize also show significant yield reductions during heat waves. High nighttime temperatures reduce rice productivity in eastern India and Bangladesh, while maize shows kernel abortion under heat stress (10). These declines directly threaten food security.
Heat also worsens pest and pathogen attacks, leading to increased pesticide dependence. Aphids, whiteflies, and fungal pathogens thrive under warmer conditions, forcing farmers to use more chemical inputs, with ecological and economic consequences (11).
Heat Stress, CO₂ Elevation, and Cellular Damage
At the cellular level, heat stress causes protein misfolding, DNA damage, and reactive oxygen species (ROS) accumulation. ROS leads to oxidative stress, damaging membranes and reducing immunity (12).
Elevated CO₂ adds complexity by altering plant nutrient composition. Although CO₂ can enhance photosynthesis, research in Nature Climate Change shows that wheat and rice grown under high CO₂ and heat contain lower protein, iron, and zinc, worsening malnutrition risks in vulnerable populations (13).
Disease Susceptibility under Heat Stress
Heat acts as a catalyst for multiple epidemics across humans, animals, and crops. Warmer conditions accelerate mosquito breeding, causing spikes in malaria, dengue, and chikungunya (14).
Heat-stressed animals show greater disease vulnerability. Mastitis incidence rises in dairy cattle due to weakened udder immunity (15), while poultry faces outbreaks of Newcastle disease under heat stress (16).
Plants also suffer heat-linked disease epidemics. Rice blast, potato late blight, and maize rust spread more aggressively in alternating cycles of heat and humidity (17).
The One Health Perspective
Heat stress demonstrates the interconnectedness of human, animal, and environmental health, requiring integrated solutions. During the 2015 Indian heat wave, thousands of people died, livestock mortality rose, crop yields collapsed, and wild birds perished. Such multi-sectoral impacts highlight the necessity of a One Health approach (18).
Integrated climate-health policies are essential to resilience. Healthcare, veterinary services, agricultural extension, forestry, and environmental planning must act in synergy. WHO has also urged countries to integrate climate adaptation into public health policy (19).
Philosophical Insights: Rishi Culture and Yajña
Ancient Indian philosophy emphasized moderation, sacrifice, and ecological harmony, offering timeless guidance for today’s heat crisis. The Vedas and Upanishads taught that humans are part of prakriti (nature), not separate from it. Exploiting nature beyond limits leads to imbalance.
Yajña, the fire ritual, carried ecological and symbolic significance. Burning herbs was believed to purify air, and modern studies suggest herbal smoke has antimicrobial effects (20). More importantly, yajña symbolized collective sacrifice, reminding us that climate adaptation must prioritize community well-being over individual gain.
The Bhagavad Gita’s philosophy of moderation offers a blueprint for sustainable living. “Yoga is excellence in action” implies that balance in work, rest, food, and resource use is essential to survival under climate extremes. By merging rishi culture with modern science, resilience can be both technological and ethical.
Statistical Comparisons and Global Evidence
The scale of the heat stress crisis is reflected in global data:
Global temperature is already 1.1 °C above pre-industrial levels (IPCC, 2021) (21).
India experienced its hottest March in 122 years in 2022, with average temperatures 1.86 °C above normal (22).
Productivity loss due to heat stress in India may cost 34 million jobs by 2030 (ILO) (3).
Dairy industry losses in India from heat stress are estimated at ₹2661 crore annually (ICAR) (6).
Wheat yield declines by 3–5% per °C rise, while rice yield drops by 10% per degree above threshold (9, 10).
Poultry mortality doubles in summer compared to winter months (7).
These figures demonstrate that heat stress is not an abstract threat but a measurable socio-economic and ecological crisis.
Conclusion
Heat stress is both a scientific and philosophical challenge that threatens human health, animal production, crop productivity, and ecological stability. Rising CO₂ levels and recurrent heat waves amplify risks of malnutrition, disease outbreaks, and biodiversity collapse.
The One Health framework provides a unifying lens for addressing heat stress. By linking medicine, veterinary science, agriculture, and ecology, society can respond holistically.
Philosophy complements science by emphasizing moderation and harmony with nature. Ancient Indian wisdom, rishi culture, yajña, and the Gita’s message of balance, remind us that survival depends on collective responsibility.
Thus, the future requires an integration of scientific interventions, policy frameworks, and philosophical ethics. Only then can humanity withstand rising heat while protecting the delicate web of life.
References
- World Meteorological Organization. State of the Global Climate Report 2023. Geneva: WMO; 2023.
- National Disaster Management Authority (NDMA). Guidelines for Preparation of Action Plan – Prevention and Management of Heat Wave. New Delhi: NDMA; 2020.
- International Labour Organization. Working on a Warmer Planet: The Impact of Heat Stress on Labour Productivity and Decent Work. Geneva: ILO; 2019.
- Glaser J, Lemery J, Rajagopalan B, Diaz HF, García-Trabanino R, Taduri G, et al. Climate change and the emergent epidemic of CKD from heat stress in rural communities: The case for heat stress nephropathy. Lancet Planet Health. 2016;1(1):e1–e5.
- Gaoua N. Cognitive function in hot environments: a question of methodology. Scand J Med Sci Sports. 2010;20 Suppl 3:48–60.
- ICAR-NDRI. Heat Stress in Dairy Cattle: Impacts and Adaptation Strategies. Karnal: ICAR-NDRI; 2021.
- Food and Agriculture Organization of the United Nations. Heat Stress in Poultry Production: Mitigation Strategies. Rome: FAO; 2019.
- Times of India. Bird deaths during Gujarat heat wave. The Times of India. 2019 Jun 13.
- Lobell DB, Sibley A, Ortiz-Monasterio JI. Extreme heat effects on wheat senescence in India. Proc Natl Acad Sci USA. 2012;109(13):765–9.
- Wassmann R, Jagadish SVK, Heuer S, Ismail A, Redona E, Serraj R, et al. Climate change affecting rice and maize: role of heat stress and adaptation strategies. Field Crops Res. 2009;111(1–2):134–43.
- Sharma HC. Climate change effects on insect pests. Indian J Entomol. 2014;76(4):340–55.
- Mittler R. Oxidative stress, antioxidants and stress tolerance. Annu Rev Plant Biol. 2002;53:451–85.
- Myers SS, Zanobetti A, Kloog I, Huybers P, Leakey ADB, Bloom AJ, et al. Increasing CO₂ threatens human nutrition. Nature Clim Change. 2014;4:686–91.
- World Health Organization. Climate Change and Vector-Borne Diseases: Global Report. Geneva: WHO; 2020.
- Bernabucci U, Lacetera N, Baumgard LH, Rhoads RP, Ronchi B, Nardone A. Metabolic and hormonal acclimation to heat stress in dairy cows. J Dairy Sci. 2010;93(2):570–81.
- Lara LJ, Rostagno MH. Impact of heat stress on poultry production. Animals. 2013;3(2):356–69.
- Chakraborty S, Tiedemann AV, Teng PS. Climate change: potential impact on plant diseases. Environ Pollut. 2000;108(3):317–26.
- Government of India. Report on the 2015 Heat Wave Impact. New Delhi: Ministry of Home Affairs; 2016.
- World Health Organization. Climate Change and Health Country Profile – India. Geneva: WHO; 2021.
- Nautiyal CS, Chauhan PS, Nene YL. Medicinal smoke reduces airborne bacteria. J Ethnopharmacol. 2007;114(3):446–51.
- Intergovernmental Panel on Climate Change. Sixth Assessment Report: Climate Change 2021. Geneva: IPCC; 2021.
- India Meteorological Department (IMD). Seasonal Climate Summary: March 2022. New Delhi: IMD; 2022.
Author Bio
Dr. Simant Kumar Nanda holds an M.V.Sc. in Pharmacology from Orissa University of Agriculture and Technology. He has authored research-based and philosophical articles across diverse themes including science, environment, spirituality, and culture. His recent works include essays on Hanuman Chalisa, Digital Dharma, and Fascination and Human Excellence. He actively contributes to seminars, webinars, and social initiatives, with a focus on integrating scientific reasoning with Indian philosophical insights.He has worked as Research Officer, ADRI and also Joint Director,Animal Wellfare in Govt of Odisha.He can be reached at drsimantkumarnanda@gmail.com | Mobile: +91-9937500810.
