CCL-81 cells heavily infected with SARS-CoV-2 virus particles. The small spherical structures in the center of the image are SARS-CoV-2 virus particles. The string-like protrusions extending from the cells are cell projections or pseudopodium. Credit: NIAID

We already know are many negative consequences to a drastically warming climate, but a new study has suggested another that feels particularly poignant given what the world has experienced in the past 2+ years.

Georgetown University researchers have published a paper that says climate change could spark the next pandemic. As the world warms, the scientists predict wild animals will be forced to relocate their habitats—likely to regions with large human populations—dramatically increasing the risk of virus transmission from animals to humans.

“We worry about [live animal] markets because bringing unhealthy animals together in unnatural combinations creates opportunities for a stepwise process of emergence—like how SARS jumped from bats to civets, then civets to people. But markets aren’t special anymore; in a changing climate, that kind of process will be the reality in nature just about everywhere,” said the study’s lead author Colin Carlson, an assistant research professor at Georgetown University Medical Center.

Indeed, we have already begun to see geographic range shifts among animals as they follow their habitats into new areas. In general, as temperatures increase, species will shift their range toward the poles and higher elevations. Studies have shown land species are moving an average of more than 10 miles per decade, while marine species are moving four times faster. Atlantic cod and Europe's purple emperor butterfly, for example, have moved more than 125 miles in a little over 10 years.

For species already at the upper northern limit of their habitat, there’s nowhere to go when others start to invade. It’s this encounter that the Georgetown scientists are worried about. As shifting mammals encounter each other for the first time, the study projects they will share thousands of viruses.

That makes it harder to predict and track where novel viruses and pathogens will/are likely to emerge. It also makes it easier for viruses to jump from animals that do not transfer zoonotic diseases to those that do—such as bats and pangolins.

According to the study results, published in Nature, animal habitats will move disproportionately in the same places as human settlements, creating new hotspots of spillover risk.

“Much of this process may already be underway in today’s 1.2˚ warmer world, and efforts to reduce greenhouse gas emissions may not stop these events from unfolding,” the study warns.

An additional important finding is the impact rising temperatures will have on bats, which account for the majority of novel viral sharing. Their ability to fly will allow them to travel long distances, likely spreading any viruses they may be harboring. Because of their central role in viral emergence, the greatest impacts are projected in southeast Asia, a global hotspot of bat diversity.

To fight the emergence of more novel pathogens as climate change restructures habitats, the study authors recommend pairing wildlife disease surveillance with real-time studies of environmental change.

“When a Brazilian free-tailed bat makes it all the way to Appalachia, we should be invested in knowing what viruses are tagging along,” says Carlson. “Trying to spot these host jumps in real-time is the only way we’ll be able to prevent this process from leading to more spillovers and more pandemics. We’re closer to predicting and preventing the next pandemic than ever. This is a big step toward prediction—now we have to start working on the harder half of the problem.”

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