If last year’s climate change fueled the megafocs and the global pandemic has taught us something, it’s the interconnection we have between ourselves and our environment. Now, we have some first clues that climate change and the cause of the pandemic can also be related, through bats.
Bats have a notorious ability to coexist with viruses that destroy other animals. While their superpowerful immune system has been a blessing to them (allowing these aerial mammals to thrive around the world), it is a curse to the rest of us as they carry these viruses wherever they go.
Now, a new study found that as the climate has warmed over the past century, rising sunlight, carbon dioxide and changes in precipitation turned the tropical scrublands of the south. China in savannas and forests, the main habitat of bats. And more than 40 new bat species were installed.
“Understanding how the global distribution of bat species has changed as a result of climate change may be an important step in reconstructing the origin of the COVID-19 outbreak,” said Cambridge University zoologist Robert Beyer.
To investigate, Beyer and colleagues used data on the world’s vegetation, temperature, rainfall, cloud cover, and vegetation requirements of the world’s bat species to construct a map of their distributions in the early twentieth century. They then compared this to the current species distribution.
“As climate change altered habitats, species left some areas and moved to others, carrying viruses,” Beyer explained. “This not only altered regions where there are viruses, but probably allowed new interactions between animals and viruses, leading to the transmission or evolution of more harmful viruses.”
Change in global bat distribution since 1901. (Beyer et al, 2021)
Three out of four infectious diseases emerging in humans are zoonotic diseases: they come from animals. And coronaviruses make up more than a third of all bat viruses sequenced. The basic components of the 2002 SARS pandemic were found in bats from a single cave, and their bodies are now the main suspects in having developed the SARS-CoV-2 precursors.
Among them, the 40 relatively recent species of migratory bats in the Chinese province of Yunnan carry more than 100 types of coronavirus. Genetic testing suggests that the ancestor of SARS-CoV-2 comes from this same region.
Most of these coronaviruses cannot infect us. And now some species of bats are being mistakenly processed by other species that have inadvertently wreaked havoc on us, even though these animals play a crucial role in our ecosystems. At least 500 species of plants depend on the pollination of bats (such as bananas, mangoes, and agave), other plants depend on their poop, and some species keep insects under control (including annoying disease-spreading mosquitoes) by devouring them.
But our relentless march towards remaining natural habitats, through processes such as deforestation, which also drive climate change, increases our interactions between these animals and, therefore, our chances of finding their viruses. Degraded habitats also stress and weaken the immune system of the animals inside, providing more chances for viruses to mutate into something that can jump through species barriers.
“Among endangered wildlife species, people with population reductions due to exploitation and habitat loss shared more viruses with humans,” a study found last year.
Beyer and the team warn that we do not yet know the exact origin of SARS-CoV-2, so its inferences are not yet conclusive and additional studies based on different vegetation and using different models are needed to corroborate its results. Other variables that may affect bat distribution should also be investigated, such as invasive species and pollution.
And while the correlation is not the same as causality, a growing group of research suggests that climate change is a driver of pathogens that infect new hosts. We even have examples where historical global climate change has been associated with environmental alterations that 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 Hawaii, Manoa .
To reduce these risks, Beyer and colleagues strongly recommend introducing measures to limit interactions between people and wildlife, including the imposition of strong regulations on wildlife hunting and trade, discouragement of dietary habits, and wildlife-dependent medicines and the establishment of strict animal welfare standards on farms, markets and vehicle transportation. To do this, we must take into account the socioeconomic needs that drive these practices that point to their work.
Protecting natural habitats is also crucial to keeping species healthy, a measure that can also help mitigate climate change.
“Given the possibility generated by our analysis that global greenhouse gas emissions may have been a factor that has contributed to the outbreaks of SARS-CoV-1 and SARS-CoV-2, we echo the demands for mitigation climate change, including as part of COVID-19 economic recovery programs, ”urges the team.
This research was published in Total Environmental Science.