In 2020, Covid-19 was holding the world hostage. That year, Cyclone Amphan struck the Sundarbans which stretches across India and Bangladesh. The combined effect of these two assaults on human health and development was devastating. Lives were lost to both, but livelihoods, too, were endangered. Lockdowns, illnesses, restricted mobility, hospitalisations, home isolations and quarantines deprived people of opportunities to earn income. Accessing health and social services, too, became difficult due to pandemic-related restrictions on movement. Cyclone Amphan not only blocked access to services but also destroyed natural resources, therefore compromising health and nutrition.
The calamitous conjunction of climate change-related extreme weather events and disease pandemics is likely to be a recurring threat in the future. As the United Nations Office for Disaster Risk Reduction (UNDRR) noted in 2022, “The climate emergency and the systemic impacts of the Covid-19 pandemic point to a new reality.” As the world grows warmer and pathogenic microbes emerge more frequently, we need to recognise their connections so we can direct both mitigation and adaptation responses in a concerted manner. We must address the common causes and the cascading consequences of one impacting the other.
Deforestation is a major cause of global warming. It also removes the natural barriers that prevent microbial migration from wildlife to veterinary populations which live within human habitats. As animals confined to forests are driven to seek new shelters, viruses and vectors which co-existed with them also move out. This enables an easy spillover across species to new hosts—animals captive-bred for food, domesticated pets and also humans. When people who are immunologically naive to these unfamiliar microbes are infected, they develop serious illnesses.
Extensive deforestation results from: urban growth, expansion of agriculture to feed a growing human population as well as hordes of captive-bred animals, and logging and extractive industries (mining). Agriculture (which includes animal breeding) is responsible for 29% of global greenhouse gas emissions and 80% of global deforestation. Deforestation heats the planet and also lets loose microbes roam the world. As meat consumption goes up, greenhouse gas emissions rise as a consequence of industry-scale factory farming of animals bred for slaughter. Animals confined in crowded spaces offer microbes many opportunities for multiplication and mutation, triggering outbreaks among them and further transmission to humans.
Travel by humans and mechanised transport of goods are common contributors to climate change and pandemics. The use of fossil fuels has risen sharply over the last century, with extensive travel through mechanised transport on land, in air and water. Compared to 70 years ago, people are travelling much more—locally, within countries and internationally—for employment, education, trade, tourism and even for socialisation. This has accelerated global warming. As people commute fast and far, microbes hitch a ride and travel within and across countries at a speed never before possible. Climate change and pandemics commute using the same vehicles.
Global warming also results in the rise of vector-borne diseases. As the scorching heat gets worse by the day, mosquitos become athletic and spread farther to reach higher altitudes which become more permissive for their growth. Malaria, dengue and chikungunya affect many, as warm weather provides a longer transmission window and reduces the extrinsic incubation period. Flooding as well as heat-related drinking water scarcity, both caused by climate change, raise the risk of water-borne diseases.
Non-communicable diseases and mental health disorders, too, increase with climate change. As heat rises intolerably, risk of brain strokes, heart attacks, circulatory collapse and kidney failure increases, with dehydration playing a major role. Pre-existing mental health disorders are aggravated. People will also exhibit anxiety, depression and aggressive behaviour. These will stress the health system. As distressed climate refugees move to other lands, there is the risk of transmitting or contracting microbial infections. Climate change, epidemics and health system overloads are therefore knit together.
Extreme weather events disrupt health services by damaging healthcare infrastructure, hindering the mobility of healthcare personnel and patients seeking care while also causing physical harm to some healthcare providers. Such disruptions can hinder healthcare and seriously undermine the efforts for intensified health service provision needed during a pandemic.
The health sector is not just a hapless victim in these scenarios but also an unwitting villain, responsible for around 5% of greenhouse emissions. Its contributions to climate change are through extensive use of energy, water, disposable equipment and certain types of anaesthetic gases such as desflurane (which has 2,500x greater potential for global warming than CO2).
As per international NGO Health Care Without Harm, the global healthcare sector generates greenhouse gas emissions equivalent to 514 coal-fired power plants. It is estimated that 71% of the emissions from the health sector emanate from its supply chains, 17% directly from healthcare facilities and 12% from purchased electricity. There is now a global movement to enable the health sector to reach a zero-emission target by 2050, led by the Alliance for Transformative Action on Climate and Health (ATACH), a WHO-led initiative.
We are living in a world of increasing complexity. Scottish-American naturalist John Muir observed several decades ago: “When we try to pick out anything by itself, we find it is hitched to everything else in the universe.” Climate change is destabilising many components of that complex web. Even as we transform health systems to become climate-smart and disaster-resilient, we must contain climate change with utmost urgency. We owe it both to ourselves and future generations.
(Views are personal)
Dr K Srinath Reddy
Cardiologist, epidemiologist and Distinguished Professor of Public Health, PHFI