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Has Climate Change Impacted Past and Present Pandemics?

By: Simantini Dey


Last Updated: June 05, 2021, 19:39 IST

Photo for representation.

Photo for representation.

Many of the root causes of climate change also increase the risk of pandemics.

Until now, there has been no direct evidence to prove a correlation between climate change and the COVID-19 pandemic, although there is a growing consensus among the scientific community that climate change affects the ways species interact, humans and species migrate, and humans face the risk of infectious diseases, which are likely to be significant factors in propelling pandemics.

According to a report by the Harvard School of Public Health, many of the root causes of climate change also increase the risk of pandemics. Deforestation, which occurs mainly for agricultural purposes, is the most significant cause of habitat loss worldwide. Loss of habitat forces animals to migrate and potentially contact other animals or people and share germs. Historically, Climate change has also been a contributing factor in the spread of infectious diseases (which causes most pandemics). And, with urban crowding, wet markets for wild game, migration due to environmental reasons, many scientists, including Anthony Fauci, have speculated that the world has just entered a pandemic era with COVID-19, and there are more pandemics in store for us in the future.

“We already know that environmental factors like deforestation and desertification play critical roles in the emergence of new diseases. Bats are a good example. If you cut down the trees where the bats live, they don’t just disappear; they come live in people’s backyards and farms instead. That increases the likelihood that a person will be exposed to microbes that live in bats such as Ebola, Nipah, rabies and other pathogens. Bat movements related to deforestation have been pinpointed as the culprits in outbreaks of Ebola and Nipah virus among others," pointed out Sonia Shah, the author of Pandemic: Tracking Contagions, from Cholera to Ebola and Beyond.

Shah added that Climate change more generally alters the ranges of pathogens and insects that spread pathogens such as malaria, Zika, dengue, chikungunya and yellow fever. “Warming seas alter the distribution of water-borne pathogens such as cholera. In some places, these changes could mean a pathogen disappears from a certain area. But in other places, pathogens will emerge in people who’ve never been exposed to them before. That’s a recipe for more outbreaks since they won’t have any immunity," she explained.


According to ANI, a report published by researchers at the University of California, Berkeley, the Politecnico di Milano (Polytechnic University of Milan) and the Massey University of New Zealand recently claimed, “Global land-use changes including forest fragmentation, agricultural expansion and concentrated livestock production are creating ‘hot spots’ favourable for bats that carry coronaviruses and where conditions are ripe for the diseases to jump from bats to humans."

Souvik Bhattacharjya, Associate Director at the Resource Efficiency and Governance Division in TERI, told News18.com that, “When a lot of land-use changes happen, we tend to get exposed to more wildlife, if not directly then indirectly. Nonetheless, this exposure might threaten our health, apart from obviously being harmful to the environment.

Therefore, when forests or natural habitats are destroyed, they can result in an outbreak of diseases."

Virologist Dr Deepak Sehgal, Professor and Head of Department of Life Science at Shiv Nadar University, pointed out, “It has been observed that there is a reduction in immunity in summers, and often people catch the flu or suffer from allergies. Due to reduced immunity, the chances of people falling prey to COVID are higher. However, there is scientific literature that counters this view.

“According to a paper published in the journal Nature, ‘visual inspection of world maps shows that coronavirus disease 2019 (COVID-19) is less prevalent in countries closer to the equator, where heat and humidity tend to be higher.’ Therefore, it is difficult to predict if the weather has any significant impact on the spread of COVID because a body of scientific literature on COVID is yet to develop. Under such circumstances, to say that weather has an impact on covid would be premature," he added.

Rushikesh Chavan, who heads The Habitats Trust explained: “One of the major factors responsible for spreading infectious diseases is human migration. We travel far more than our previous generations did, and obviously, there is also an increase in material exchanges. Therefore, the chances of our exposure to a pathogen are far more likely now than it was in previous generations."

“The changing climatic patterns, with increased use of wildlife for consumption, the way they are stored, and sometimes, they are even illegal and therefore, smuggled in — these kinds of conditions create an environment for pathogens to hide and survive. We may not feel the climate change impact as deeply in our lives till now, but for a single-cell organism, that change is huge, and they adapt to it. Once they adapt and mutate, if they find ways to jump into the human body, we do not have an immune system to combat that, and that is how most outbreaks begin," pointed out Chavan.

“We have had these outbreaks throughout history. But, the terrifying thing that we are slowly beginning to understand is that the magnitude, intensity and frequency of these pandemics/epidemics is markedly higher now, and moving forward, we are likely to see many more of such events," he concluded.

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first published:June 05, 2021, 19:37 IST
last updated:June 05, 2021, 19:39 IST