New research suggests that climate change could have caused the COVID-19 outbreak by forcing bats to migrate to new climates.
A new study published today in the journal Science of the Total Environment provides the first evidence of a mechanism by which climate change could have played a direct role in the evolution of SARS-CoV-2, the virus that caused the COVID-19 outbreak.
Supported by the European Research Council, the study revealed large-scale changes in vegetation in the southern Chinese Yunnan province, and adjacent regions in Myanmar and Laos, over the last century. Climatic changes including increases in temperature, sunlight, and atmospheric carbon dioxide have changed natural habitats from tropical shrubland to tropical savannah and deciduous woodland. This created a suitable environment for the many bat species that predominantly live in forests.
Dr Robert Beyer, a researcher in the University of Cambridge’s Department of Zoology and first author of the study, said: “Climate change over the last century has made the habitat in the southern Chinese Yunnan province suitable for more bat species. 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.”
The link between changes in vegetation and new bat-borne coronavirus
The researchers created a map of the world’s vegetation from 100 years ago, using records of temperature, precipitation, and cloud cover. Then they used information on the vegetation requirements of the world’s bat species to work out the global distribution of each species in the early 1900s. Comparing this to current distributions allowed them to see how bat ‘species richness’ – the number of different species – has changed across the globe over the last century due to climate change.
The number of coronaviruses in an area is closely linked to the number of different bat species present. The study found that an additional 40 bat species have moved into the southern Chinese Yunnan province in the past century, harbouring around 100 more types of bat-borne coronavirus. This ‘global hotspot’ is the region where genetic data suggests SARS-CoV-2 may have arisen.
Beyer added: “As climate change altered habitats, species left some areas and moved into others, taking their viruses with them. 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 world’s bat population carries around 3,000 different types of coronavirus, with each bat species harbouring an average of 2.7 coronaviruses. An increase in the number of bat species in a particular region, driven by climate change, may increase the likelihood that a coronavirus harmful to humans is present, transmitted, or evolves there.
From bats, to pangolins, to humans
The region identified by the study as a hotspot for a climate-driven increase in bat species richness is also home to pangolins, which are suggested to have acted as intermediate hosts to SARS-CoV-2. The virus is likely to have jumped from bats to these animals, which were then sold at a wildlife market in Wuhan. The researchers emphasised the need to limit the expansion of urban areas, farmland, and hunting grounds into natural habitat to reduce contact between humans and disease-carrying animals.
Professor Andrea Manica in the University of Cambridge’s Department of Zoology, who was involved in the study, said: “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.”