The study found large-scale changes in the type of vegetation in the southern Chinese Yunnan province and adjacent regions in Myanmar and Laos over the last century. Changes in temperature, sunlight, and atmospheric carbon dioxide have altered the natural environment from tropical shrubland to tropical savannah and deciduous woodland, creating a suitable environment for many bat species that predominantly live in forests.
"Climate change over the last century has made the habitat in the southern Chinese Yunnan province suitable for more bat species," said Dr. Robert Beyer, a researcher in the University of Cambridge's Department of Zoology and first author of the study, in a press release. “Understanding how the global distribution of bat species has shifted as a result of climate change may be an important step in reconstructing the origin of the COVID-19 outbreak.”
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The number of coronaviruses in an area is linked to the number of different bat species present, according to a press release regarding the study—and an additional 40 bat species have moved into the southern Chinese Yunnan province in the past century, bringing with them around 100 more types of bat-borne coronavirus. Genetic data suggests that this region may be where SARS-CoV-2 arose. This region is also home to pangolins, which may have acted as intermediate hosts to SARS-CoV-2: The theory suggests that bats transmitted the virus to pangolins, which were then sold at a wildlife market in Wuhan, where the initial human outbreak occurred.While most coronaviruses carried by bats cannot jump into humans, several coronaviruses that infect humans are likely to have originated in bats, including Middle East Respiratory Syndrome CoV and SARS CoV-1 and CoV-2.
"As climate change altered habitats, species left some areas and moved into others—taking their viruses with them,” Beyer said. “This not only altered the regions where viruses are present, but most likely allowed for new interactions between animals and viruses, causing more harmful viruses to be transmitted or evolve.”
The researchers who performed the study called on policymakers to acknowledge the role of climate change in outbreaks of viral diseases, and to address climate change as part of COVID-19 economic recovery programs.
"The COVID-19 pandemic has caused tremendous social and economic damage. Governments must seize the opportunity to reduce health risks from infectious diseases by taking decisive action to mitigate climate change," said Professor Andrea Manica in the University of Cambridge's Department of Zoology, who was involved in the study.
"The fact that climate change can accelerate the transmission of wildlife pathogens to humans should be an urgent wake-up call to reduce global emissions," added Professor Camilo Mora at the University of Hawai'i at Manoa, who initiated the project.
The researchers also emphasized that expansion of urban areas, farmland, and hunting grounds into natural habitats needs to be limited, in order to reduce contact between humans and disease-carrying animals.
