Man-made climate change “may have played a key role” in the coronavirus pandemic. That is the conclusion of a new study that examined how climate change has transformed forests in Southeast Asia, resulting in an explosion of bat species in the region.
The researchers found that due to changes in vegetation over the past 100 years, another 40 species of bats moved to the region, taking with them another 100 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 started the global COVID-19 pandemic originated in bats in Yunnan province, southern China, or surrounding areas before crossing paths with humans.
These findings worry scientists about the likelihood that climate change will make future pandemics more likely.
“If bats carrying about 100 coronaviruses expanded into a new area due to climate change, then it would be likely that this would increase, rather than decrease, the chance that a coronavirus harmful to humans will be present, transmitted or evolved in this area. “. explains Dr. Robert Beyer, lead author of the study and a researcher at the University of Cambridge.
Ng Han Guan / AP
The 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 bat species, they determined the global distribution of each species in the early 20th century.
They then compared this to current bat populations. The results reveal that the richness of bat species – the number of different bat species found in a given area – flourished in this Southeast Asian pocket more than anywhere else on Earth.
The image below, from the study, shows how the forests of southern China, Myanmar and Laos have changed over the past century, improving bats’ preferred habitat and allowing more species to proliferate. This distinctive target over the region shows the increase in the richness of bat species. (The study does not consider the general size of the population, only the diversity of bat species in the area.)
Dr. Robert Beyer
According to the authors, climate changes, such as increases in temperature, sunlight and carbon dioxide, which affect the growth of plants and trees, have changed the composition of vegetation in southern China, transforming tropical undergrowths into tropical savannas and deciduous forests. This type of forest, say the authors, is more suitable for bat species.
The study calls this area in Southeast Asia “a global hotspot” for bat species and points to genetic data that suggests that SARS-CoV-2, the virus that causes COVID-19, originated in this region.
This, say the authors, provides the first evidence that climate change may 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 place where SARS-CoV-2 probably originated,” said Beyer. “This increase suggests a possible mechanism for how climate change may have played a role in the origin of the pandemic.”
A team of researchers from the World Health Organization was finally allowed in Wuhan, China, in January, to investigate the source of the outbreak, which was first reported in that city a little over a year ago. One of the main theories among scientists is that the virus originated in bats before passing on to humans, potentially through an animal host such as pangolins. Some of the first cases were linked to a wildlife market in Wuhan. But, as of now, this is just a theory, and researchers are just beginning to formally investigate the origins of the pandemic.
Dr. Rick Ostfeld, a specialist in disease ecology at the Cary Institute for Ecosystem Studies in Millbrook, New York, finds the research attractive, although he does not agree with all of his conclusions. He says it is not surprising that climate change has transformed forests and bat communities. He also agrees with the study’s authors that animal movement can help spread viruses.
“Moving animal communities in a region can have strong impacts on disease transmission, exposing animal hosts to new pathogens,” he said.
But he is cautious in drawing conclusions beyond that.
“The link to the emergence of coronavirus is highly speculative and seems unlikely,” said Ostfeld.
“What the study appears to be wrong is the assumption that increasing the diversity of bats (which they postulate) leads to an increased risk of a virus transmitted by bats spreading to humans. That is simply not the case,” he said. it. “The vast majority of bats are harmless to humans – they do not harbor viruses that can make us sick. Therefore, adding more of these species does not increase the risk.”
Kate Jones, professor of ecology and biodiversity at University College London, is also somewhat cautious. She said: “Climate change certainly has a role to play in changing the distribution of species to increase ecological risk. However, overflow risk is a complex interaction not only of ecological risk, but also of human exposure and vulnerability. “
Beyer agrees that “caution is justified” when it comes to connecting climate change directly to the pandemic because, as he explains, it assesses the degree to which climate change has contributed to any stage between a bat carrying the virus and a human being infected it will take a lot more work. In particular, he says, this involves the use of epidemiological models that analyze the interactions of different species and viruses in space and time.
Although it is widely known that the exponential growth of the human population and our unbridled exploration of the natural world, as destroying forests and expanding the animal trade, is increasing the risk that contagious pathogens can more easily jump from animals to humans, it has been less clear to what extent factors of climate change in.
AP
However, over the past century, because of man-made climate change, many ecosystems have warmed up – sometimes to varying degrees – and rainfall patterns have changed, with some areas decreasing and others increasing. These ecosystem changes are changing the habitat of many species, putting more species in contact with each other, potentially allowing viruses to spread more easily.
When asked about the climate connections with the spread of disease, most experts agree that there is an impact, but some say that direct human actions, such as deforestation, development or animal agriculture on an industrial scale, are a major concern.
“It may happen that the increase in human populations, human movement and the degradation of natural environments through agricultural expansion have a more important role to play in understanding the SARS-CoV-2 overflow process,” explained Jones.
Ostfeld noted: “We can predict which species of wildlife are most likely to carry pathogens that can make people sick. They are usually those that thrive when we replace natural habitat (such as forests and savannas) with agriculture, residential developments and shopping malls. “
Beyer has no problem with these assessments. “We fully 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 put many animals and humans carrying pathogens in the first place,” he said. it.
But, given the findings of his research on how the climate reshaped the region, Beyer feels that climate change could be a significant factor.
“Climate change can lead to where these animals occur; in other words, climate change can move pathogens closer to humans. It can also move a species that carries a virus into the habitat of another species to which the virus can jump. – a step that may not have taken place without climate change, and that could have important long-term consequences for the virus’s next destination. “
Beyer also sees climatic connections in addition to the increase in bat species. “In some cases, higher temperatures can increase the viral load in the species, which can make transmission of the virus more likely,” he said. “E: Increasing temperature can increase the tolerance of viruses to heat, which, in turn, can increase infection rates, since one of our main defense systems against infectious diseases is the increase in 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 broad consensus that, in the future, climate change will be a growing driver of emerging infectious diseases and pandemics.
“Climate change will change the geographic distributions of species carrying pathogens in such a way that they overlap with species they have not overlapped with before,” said Beyer. “These new interactions will provide dangerous opportunities for viruses to spread and evolve.”
“Climate change is definitely an important factor in the emergence and spread of disease. It can increase transmission in several ways,” said Ostfeld. “So yes, climate change definitely concerns me as a driver for future pandemics.”