If last year’s climate change fueled megafires and the global pandemic taught us anything, it’s how much we are all connected to each other and to our environment. Now we have some early hints that both climate change and the cause of the pandemic could also be intertwined – through bats.
Bats have a notorious ability to live with viruses that destroy other animals. While their super-powered immune systems have been a boon to them – allowing these airborne mammals to thrive around the world – it’s a bane to the rest of us, as they carry these viruses with them wherever they go.
Now, a new study found that as the climate has warmed over the past century, increases in sunlight, carbon dioxide, and changes in precipitation turned southern China’s tropical shrubs into savannas and forests – excellent habitat for bats. And more than 40 new bat species came in.
“Understanding how the global distribution of bat species has shifted due to climate change could be an important step in reconstructing the origins of the COVID-19 outbreak,” said Cambridge University zoologist Robert Beyer.
To investigate this, Beyer and colleagues used data on the vegetation, temperature, precipitation, cloud cover, and vegetation requirements of the world’s bat species to map their distribution in the early 20th century. They then compared this with the current species distribution.
“When climate change changed habitats, species left some areas and migrated to others – taking their viruses with them,” explains Beyer. “This not only changed the regions where viruses are present, but most likely also allowed new interactions between animals and viruses, allowing more harmful viruses to be transmitted or evolved.”
Change in global bat distribution since 1901. (Beyer et al, 2021)
Three of the four new infectious diseases in humans are zoonotic diseases – they come from animals. And coronaviruses make up more than a third of all bat viruses sequenced. The building blocks of the 2002 SARS pandemic were found in single cave bats, and now their bodies are prime suspects of having the precursors to SARS-CoV-2.
Together, the 40 relatively recent migrating bat species to China’s Yunnan province carry more than 100 species of coronaviruses. Genetic evidence suggests that the ancestor of SARS-CoV-2 is from the same region.
However, most of these coronaviruses cannot infect us. And now some species of bats are being falsely prosecuted for other species that inadvertently devastate us, even though these animals play a vital role in our ecosystems. At least 500 plant species depend on bat pollination (such as bananas, mangoes and agave), other plants depend on their poop, and some species control insects (including pesky, disease-spreading mosquitoes) by devouring them.
But our relentless march further and further into remaining natural habitats, through processes, such as deforestation, which are also driving climate change, increases our interactions between these animals and thus our chances of encountering their viruses. Degraded habitats also stress and weaken the immune systems of the animals in them, giving viruses more opportunities to mutate into something that can jump over species barriers.
“Among endangered species, those with population declines due to exploitation and habitat loss shared more viruses with humans,” a study found last year.
Beyer and team caution that we do not yet know the exact origin of SARS-CoV-2, so their inferences are not yet conclusive and further studies based on different vegetation and the use of different models are needed to confirm their findings. Other variables that may affect bat distribution, such as invasive species and pollution, should also be explored.
And while correlation does not equate to causality, a growing body of research suggests that climate change is a driver of pathogens infecting new hosts. We even have examples where historical global climate change has been linked to environmental disturbances that have led to emerging infectious diseases.
“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,” said biogeographer Camilo Mora of the University of Hawai’i, Manoa.
To mitigate these risks, Beyer and colleagues strongly recommend introducing measures to limit human-animal interaction, including imposing strict rules on the hunting and trade of wildlife, discouraging animal-dependent eating habits and medicinal products. practices, and establishing strict animal welfare standards on farms, markets and transportation vehicles. To do this, we need to consider the socioeconomic needs driving these practices, they note in their paper.
It is also crucial that we protect natural habitats to keep species healthy, a measure that can also help mitigate climate change.
“ Given the possibility raised by our analysis that global greenhouse gas emissions may have been a contributing factor in the SARS-CoV-1 and SARS-CoV-2 outbreaks, we reiterate the calls for a decisive limitation of climate change, also as part of COVID-19. economic recovery programs, ”the team insists.
This research is published in the Science of the total environment.