Are climate-related changes in bat diversity responsible for COVID-19?

M.Most of the evidence scientists have produced since the pandemic began suggests that bats are the likely source of the coronavirus that causes COVID-19. A shift in the global distribution of winged mammals due to climate change could be responsible for the recent disease outbreaks, according to a study published on Jan. 26 Science of the whole environment.

The paper’s authors estimate that bat diversity has increased most in an area that includes Myanmar, Laos and southern China – where SARS-CoV-2 is likely to originate – increasing the likelihood of a bat-borne disease spreading to humans is increased.

“Our estimates complement earlier studies in which the effects of climate change on the global spread of pathogen-bearing wild animals were highlighted,” says Robert Beyer, research associate at the Potsdam Institute for Climate Impact Research in Germany and lead author of the study The scientist in an email. “We know that these shifts in species ranges can play a critical role in the transmission and development of harmful viruses. It is therefore important to consider the effects of climate change also in relation to emerging infectious diseases and global public health. “

Other experts say these results should be interpreted with caution because the predictions are difficult to verify. “Overall, I am not convinced that the analysis is robust enough to reach the conclusions it claims,” ​​says Matthew Struebig, a nature conservation scientist at the University of Kent who was not involved in the research The scientist in an email.

We know that these shifts in species ranges can play a critical role in the transmission and development of harmful viruses.

– Robert Beyer, Potsdam Institute for Climate Impact Research

Compared to other mammals, bats carry more than their fair share of potentially zoonotic viruses, pathogens that could infect humans. Each type of fur flier is home to an average of 2.7 strains of coronavirus, by one estimate. It follows that as the diversity of bats increases in a region, the diversity of these spiked viruses also increases. If climate change has changed the distribution of bats – and the pathogens they carry – this could affect the likelihood of a disease spreading to humans, Beyer and his colleagues suspected.

“It’s a numbers game,” says Sarah Olson, a wildlife epidemiologist with the Wildlife Conservation Society in New York who was not involved in the research. “The more [viral] The more diverse you are, the more likely it is that you will encounter viruses that have the potential to infect people. “

To estimate how global bat diversity changed between 1901 and 1930 and between 1990 and 2019, Beyer and his colleagues used estimates of temperature, precipitation, sunshine and carbon dioxide to predict the global distribution of different types of vegetation. By comparing the vegetation maps with the habitat requirements and geographical boundaries of all known bat species, the team forecast the total abundance of bat species in each period.

Based on this analysis, the team identified several regions where bat diversity may have increased the most: Central Africa, scattered areas in Central and South America, and a large area in Southeast Asia that includes parts of Myanmar, Laos and the Chinese province of Yunnan. In this Asian region, researchers estimated that climate change has transformed large swaths of tropical scrubland into tropical savannahs and deciduous forests, making the region more suitable for an additional 40 bat species – and about 100 additional coronavirus strains. Since this estimated bat hotspot coincides with the regions where both SARS-CoV-1 and SARS-CoV-2 are believed to have occurred, researchers speculate that climate change may have contributed to causing these virus outbreaks.

Olson says the study “pushes us to think in new ways about drivers of emerging infectious diseases.” However, the results are speculative and “difficult, if not impossible, to validate”. The study’s conclusions are based on estimates of vegetation for the period 1901–1930 that cannot be confirmed by satellite or soil data, says Olson. And because the study relied on climate data to estimate habitat types, it ignored land use changes that could alter the suitability of bat areas.

Struebig is skeptical of the study’s connection between climate change and bat diversity. “There are too many assumptions for me to conclude that climate change could have made the pandemic more likely to occur.”

According to Struebig, the analysis is based on bat distribution data from the International Union for Nature Conservation (IUCN). “As a member of the IUCN Bat Specialist Group, I can tell you that the information we have available for mapping distributions is completely inadequate. Many species are not fully assessed, and. . . Very little is known about optimal or preferred types of vegetation. . . . The study estimates that the bat fauna in southern China and neighboring countries has increased by more than 40 species in around 120 years. To put this into perspective, the number of bat species in Myanmar would double in a little over a century! A look back at old species reports and ecological studies from the region shows that this simply did not happen. “

Olson says that while the results do not provide conclusive evidence that bat distribution has affected the pandemic, the study does help to draw attention to the problem. “We change environments in ways we don’t really understand or appreciate until we have an event like this [the COVID-19 pandemic] It lets us reevaluate our relationship with nature, ”she says. “I think [the study] Art opens the door and says, “Hey, here are some other ways we are affecting the environment that could change the range and biodiversity.” And we have to pay attention to that when it comes to it [understanding] newly emerging infectious diseases can develop further. “

RM Beyer et al., “Shifts in global bat diversity suggest a possible role for climate change in the development of SARS-CoV-1 and SARS-CoV-2”. Sci Total Environ, doi: 10.1016 / j.scitotenv.2021.145413, 2021.



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