Human-induced climate change “may have played a key role” in the coronavirus pandemic. This is the conclusion of a new study that examined how climate change has transformed the forests of Southeast Asia, causing an explosion of bat species in the region.
The researchers found that due to changes in vegetation over the past 100 years, an additional 40 bat species have moved to the region, carrying with them 100 more types of coronavirus transmitted by bats. Bats are known carriers of coronavirus, with several species carrying thousands of different types. Many scientists believe that the virus that caused the global pandemic COVID-19 originated in bats in Yunnan Province, southern China, or neighboring areas before it crossed with humans.
These findings have worried scientists about the likelihood that climate change will make future pandemics more likely.
“If bats carrying around 100 coronaviruses spread to a new area due to climate change, it seems likely that this will increase, rather than decrease, the chance that a coronavirus that is harmful to humans will be present, transmitted or evolve in this area “. explains Dr. Robert Beyer, lead author of the study and researcher at Cambridge University.
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Researchers used climate records to create a map of the world’s vegetation as it was a century ago. Using knowledge of the type of vegetation required by different species of bats, they determined the overall distribution of each species in the early twentieth century.
They then compared this to current bat populations. Their results reveal that the richness of bat species – the number of different bat species found in a given area – has flourished in this pocket of Southeast Asia more than anywhere else on Earth.
The following image, from the study, shows how the forests of southern China, Myanmar and Laos have changed over the past century, improving bat-favored habitat and allowing more species to proliferate. This distinctive bullseye over the region shows the increasing richness of bat species. (The study does not take into account overall population sizes, only the diversity of bat species in the area.)
Dr. Robert Beyer
According to the authors, climate changes such as rising temperatures, sunlight and carbon dioxide, which affect the growth of plants and trees, have changed the composition of vegetation in southern China, making them tropical shrubs in tropical savannah and deciduous forest. According to the authors, this type of forest is more suitable for bats.
The study says this area of Southeast Asia is “a global access point” for bat species and points to genetic data suggesting that SARS-CoV-2, the virus that causes COVID-19, originated in this region.
This, according to the authors, provides the first evidence in a way that climate change could have played a direct role in the emergence of the virus.
“We estimate that over the past century, climate change has caused a significant increase in the number of bat species in the location where SARS-CoV-2 probably originated,” Beyer said. “This increase suggests a possible mechanism for how climate change may have played a role in the origin of the pandemic.”
There was a team of researchers from the World Health Organization he finally entered Wuhan, China, in January to investigate the source of the outbreak, which was first reported in this city a little over a year ago. An important theory among scientists is that the virus originated in bats before making the leap to humans, potentially through an animal host such as pangolins. Some of the first cases were related to a wildlife market in Wuhan. But right now, this is just a theory and researchers are just beginning to formally investigate the origins of the pandemic.
Dr. Rick Ostfeld, an expert in disease ecology at the Cary Institute of Ecosystem Studies in Millbrook, New York, finds the research compelling, though he disagrees with all the findings. He says it’s no surprise that climate change has been found to have transformed forests and bat communities. The authors of the study also agree that the movement of animals can help spread viruses.
“The movement of animal communities around a region can have a strong impact on disease transmission by exposing animal hosts to new pathogens,” he said.
But it is prudent when it comes to drawing conclusions further.
“The link to the appearance of coronavirus is highly speculative and seems unlikely,” Ostfeld said.
“What the study looks like is going wrong is the assumption that increasing bat diversity (which they postulate) leads to a higher risk of a bat-transmitted virus jumping to humans. It’s just not the case,” he said. to say. “The vast majority of bats are harmless to humans: they don’t harbor viruses that can harm us. So adding more of these species doesn’t increase the risk.”
Kate Jones, a professor of ecology and biodiversity at University College London, is also a little cautious. He said: “Climate change certainly has a role to play in changing the distribution of species to increase ecological danger. However, the risk of spillage is a complex interaction not only of ecological danger but also of ecological risk. exposure and human vulnerability “.
Beyer does agree that “caution is well justified” in connecting climate change directly to the pandemic, as he explains how he assesses the degree to which climate change contributed to any stage between a bat carrying the virus and an infected human will take much longer to work. In particular, he claims, this involves the use of epidemiological models that analyze the interactions of different species and viruses across space and time.
Although it is widely understood that the exponential growth of the human population and our unbridled exploitation of the natural world, as destroying forests and expanding the file animal trade, is increasing the risk of contagious pathogens it can make the leap from animals to humans more easily, it has become less clear to what extent factors of climate change a.
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However, over the past century, due to climate change caused by humans, many ecosystems have warmed (sometimes to varying degrees) and precipitation patterns have changed, with some areas becoming less and others with more. These ecosystem changes are changing the habitat of many species and bringing more species into contact, which can allow viruses to spread more easily.
When asked about climate connections to the spread of the disease, most experts agree that there is an impact, but some say that direct human actions such as deforestation, development or industrial agriculture on an industrial scale are a greater concern.
“It may turn out that increases in human populations, human movement, and degrading natural environments through agricultural expansion have a more important role to play in understanding the process of spilling SARS-CoV-2,” he explained. Jones.
Ostfeld noted, “We can predict which wildlife species are most likely to carry disease-causing pathogens. They are generally the ones that thrive when we replace natural habitat (such as forests and savannas) with agriculture, residential developments, and shopping malls. . “
Beyer does not question these assessments. “We absolutely agree that the expansion of urban areas, farmland and hunting grounds into natural habitats is a key factor in the transmission of zoonotic diseases: they are what bring many animals and humans together who they carry pathogens, ”he said.
But given the findings of his research on how climate reshaped the region, Beyer believes climate change can be a major driver.
“Climate change can lead to where these animals occur; that is, climate change can bring pathogens closer to humans. It can also move a species that transports a virus to the habitat of another species to which the virus it can jump, a step that might not have happened without climate change, and that could have important long-term consequences for where the virus can go. “
Beyer also sees climatic connections beyond the rise of bat species. “In some cases, higher temperatures can increase the viral load of the species, which can make the virus more likely to be transmitted,” he said. “I: Rising temperature can increase the tolerance of viruses to heat, which in turn can increase infection rates, as one of our main systems for defending against infectious diseases is to raise body temperature ( fever) “.
While there is some caution in the scientific community about the specific impact of climate change on the current coronavirus pandemic, there is widespread agreement that, in the future, climate change will be a growing driver of infectious diseases and emerging pandemics.
“Climate change will change the geographic distributions of pathogen-carrying species so that they overlap with previously non-overlapping species,” Beyer said. “These new interactions will provide dangerous opportunities for viruses to spread and evolve.”
“Climate change is definitely an important factor in the onset and spread of disease. It can increase transmission in several ways,” Ostfeld said. “So, yes, climate change definitely worries me as a driver of future pandemics.”