Many have long since accepted the established effects of climate change — global warming, the melting of the polar ice caps and rising sea levels, to name a few. However, scientists also hypothesize that climate change may have new effects that they are not yet able to predict and now, under our present international circumstances surrounding the outbreak of a deadly pandemic, many are begging the question: are diseases related to climate change?
The suspicion likely stems from the fact that COVID-19, the strain of coronavirus that is currently infecting the human population, has never been seen in human beings before, marking it a novel development.
According to several UT scientists, diseases are not a direct product of climate change. However, climate change plays a large role in changing the way that diseases develop and spread.
According to Kristina Kintziger, associate professor in the Department of Health, no new pathogens have been created because of climate change; instead the phenomenon has allowed already existing pathogens to spread much more rapidly.
She explained that most diseases of significance in the health community are of zoonotic origins, meaning that they originate in animals and make their way to infect humans. The coronavirus is an example of one such disease.
Kintziger stated that as temperatures rise, arthropods are forced to change their breeding and and habitat patterns, allowing pathogens, which spawn disease and viruses, to spread to new areas. Furthermore, droughts brought on by climate change lead to an increased mixing of pathogens as well, as both humans and animals overcrowd the nearest water sources.
“Climate change has definitely been responsible for the spread and exacerbation of a variety of infectious and non-infectious diseases and health problems. This has occurred for many reasons,” Kintziger said.
Andrew Steen, associate professor in the Department of Earth and Planetary Sciences, seconded Kintziger’s statement about the increased spread of pathogens. He added that as climate change leads to increased agricultural failures, more people are forced to consume wild animals, leading to the further spread of pathogens.
“Climate change can cause agricultural failures, which can cause people who don’t normally hunt ‘bushmeat’ to begin to do so, which again creates new opportunities for new viruses to jump to humans,” Steen said.
Climate change leads to the increased spread of diseases through many other situations, such as overflowing sewer systems as a result of flooding, increased precipitation spreading chemicals into food and water and the introduction of new animals as they replace those who have gone extinct, leading to human interaction with new species.
Furthermore, climate change itself is not the only generator of increased disease spread; its causes, such as overcrowding and pollution, are just as culpable as well.
“The causes of climate change definitely contribute to disease development in humans. Overcrowding leads to greater mixing of people, and therefore, easier transmission of infectious diseases that are spread person-to-person. Pollution leads to a greater incidence of respiratory diseases, like asthma, particularly in vulnerable populations,” Kintziger said.
So, what does this information mean for the coronavirus in particular?
Scientists around the world have determined that the virus has natural origins and began in a bat, although they are unsure exactly how the disease spread to humans. Officials have yet to successfully determine whether the virus originated from a lab spill, where samples of a natural strain of the disease may have been held, or a wet market in Wuhan, China.
As Benjamin Auerbach, associate professor in the Department of Anthropology, explained, spillover events between animals and humans, similar to what may have occurred in the creation of the coronavirus, have led to the spread of infections in the past, and these events will likely increase as humans continue to expand across the planet.
“There were likely many spillover events (when infectious agents pass from animals to humans, like the one we are currently experiencing with SARS-CoV-2) in the past, as humans interacted with their environment; because these groups were isolated, the agent infected the local human population but never passed elsewhere,” Auerbach said. “I can say that we can probably expect to see more spillover events with the ongoing expansion of humans into previously remote ecosystems, especially given the ease by which those remote locations are linked to metropolitan areas.”
However, Auerbach is unable to connect these events specifically with climate change.
"Yet the connections with climate change are not easy to link, as the reasons why human groups choose to exploit these wild environments are varied, and the ecological circumstances for spillovers to occur and for diseases to be transmissible among humans are complex," Auerbach said. "Spillovers can occur because humans displace animals (like bats) when destroying wild habitats, increasing the contact with those species as they seek new ways to survive in a disrupted habitat. Spillovers can also occur because humans actively hunt wild species, which increases the chances for spillover events.”
Kintziger added that it is not possible to fully predict how climate change will affect the development of the coronavirus in the future. She explained that if the virus does behave similarly to the flu, however, the disease will be impacted and worsened by ongoing climate change and global warming.
“If COVID-19 proves to be similar to influenza in terms of seasonal patterns, then climate change will impact both the timing of infection and the severity of the season,” Kintziger said. “With influenza, we see that severe flu seasons were typically preceded by mild winters, and that these severe flu seasons began earlier in the year. Influenza is less transmittable in these mild winters, so not many people are infected. This yields a large susceptible population, with little immunity, the next winter.”
Because scientists have not currently determined exactly how the coronavirus made its leap from animals to humans, time will likely pass before we are able to postulate whether or not climate change played a role in the development of this modern pandemic.
Corrections have been made to this story to more accurately reflect scientific information.