How global warming could cause animal-to-human pandemics

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According to a new study, climate change will put more pressure on species to migrate and provide thousands of new opportunities for viruses to move from one species to another in the coming decades.

These occurrences may raise the likelihood of a human pandemic. Ebola, HIV, avian flu, SARS, and many scientists believe COVID-19 all began with viral transmission from wildlife and cattle to people.

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The study, published in the Nature journal, indicates how climate change and ecological changes in habitats would drive viruses' host animals to new locations where they will interact with other species for the first time.

These inter-species interactions will increase viral reservoirs, endangering endangered species and increasing the likelihood of viruses spreading to humans. 

Thomas Gillespie, a disease ecologist at Emory University states that the study stresses " there are lots of cross-species transmission events that are happening now, and many more that can happen as environments are changing."

If warming is maintained to less than 2°C above preindustrial levels, the researchers predict that hundreds of thousands of first contacts between species will occur over the next five decades, resulting in more than 4,500 viral transmissions from one species to another.

According to the findings, the majority would occur in high-elevation environments with diverse biodiversity in tropical Africa and Asia.

Similar processes will be witnessed in the decreasing expanses of species-rich tropical primary forests. Many of these locations are also where cities and crops are grown.

"Climate change is creating innumerable hotspots of future zoonotic risk or presents a zoonotic risk right now in our backyard," Colin Carlson, a disease ecologist at Georgetown University and co-author of the study, said in a press conference, using the term "zoonosis," which refers to viruses that jump between species.

Even if carbon emissions are reduced, the new study's models reveal that the increase in viral sharing occurrences is not entirely prevented. And the study reveals that some of them are already being driven by climate change.

According to Gillespie, "The bottom line is the majority of the viral sharing events are going to happen over the next 20 years and going to happen regardless of how well we mitigate climate change within that window."

Gregory Albery, who also studies disease ecology at Georgetown says the work "provides us more incontrovertible evidence that the coming decades will not only be hotter, but sicker."