Climate change isn’t just making sea levels rise and leading to epic droughts, hurricanes, wildfires, floods, and heat waves. It’s also making diseases such as Zika and yellow fever spread as mosquitos move into more areas. And a new study suggests that it may have been a factor in the current pandemic.
The study, published in the journal Science of the Total Environment, mapped changes in bat habitat in Yunnan Province in southern China and nearby areas of Myanmar and Laos, a region where SARS-CoV-2, the virus that causes COVID-19, may have originated in bats. As climate change made it warmer and sunnier in the area over the last century, and extra carbon dioxide in the atmosphere made plants and trees grow faster, some areas that were once filled with shrubs and smaller plants became forests—an ideal place for bats to live. The study found that 40 bat species moved to the area in the last 100 years, making it a hot spot for coronaviruses. The animals brought around 100 new types of coronavirus to the region, one of which is genetically similar to the virus in the current outbreak.
Climate change isn’t the only problem; as humans have destroyed wildlife habitat, it’s becoming much more likely that people come in contact with wild animals and viruses can make the jump to humans. “The expansion of urban areas, farmland, and hunting grounds into natural habitats is a key driver of zoonotic disease transmissions—they are what puts many pathogen-carrying animals and humans into contact in the first place,” study author Robert Beyer, a researcher in the University of Cambridge’s Department of Zoology, says in an email. “That being said, climate change can drive where these animals (or the animals that they got a virus from) occur; in other words, climate change can move pathogens closer to humans. It can also move a species that carries a virus into the habitat of another species that the virus can then jump to—a step that might not have occurred without climate change, and that might have major long-term consequences for where the virus can go next.”
More than 60% of emerging infectious disease events now come from animals. Bats, which carry at least 3,000 types of coronavirus, are particularly likely to be a source. The Middle East respiratory syndrome (MERS) virus likely originated in bats (before being transmitted to camels). The same is true of SARS and SARS-CoV-2; bats living in the area mapped in the study carry strains of coronavirus very similar to both of those viruses, which may have jumped from bats to palm civets and pangolins before jumping to humans via a wildlife market.
As climate change brings more bat species in contact in some areas, it’s more likely that viruses can spread and evolve in animals. Countries take steps to protect wildlife habitat and better regulate hunting and farms so humans are less likely to come into contact with infected animals that could spark the next pandemic, the study says. But it also makes one more argument for quickly cutting emissions.