As the global climate continues to warm, wild animals may be forced to relocate to areas with large human populations — increasing the likelihood of a “viral jump” that could cause the next pandemic, a new study has found.
Different mammals will encounter one another for the first time during these journeys — called “geographic range shifts” — and in doing so, they will also share thousands of viruses, according to the study, published on Thursday in Nature.
Such shifts will also pave the way for pathogens like Ebola or coronaviruses to thrive in new areas and in new types of animals, making them harder track as they traverse “stepping stone” species toward their human destinations, the authors warned.
This phenomenon will essentially normalize the risks that people today associate with wildlife trade, according to lead author Colin Carlson, an assistant research professor at the Center for Global Health Science and Security at Georgetown University Medical Center.
“We worry about markets because bringing unhealthy animals together in unnatural combinations creates opportunities for this stepwise process of emergence — like how SARS jumped from bats to civets, then civets to people,” Carlson said in a statement.
“But markets aren’t special anymore,” he continued. “In a changing climate, that kind of process will be the reality in nature just about everywhere.”
To draw their conclusions, the scientists conducted a comprehensive assessment of how climate change will transform the “global mammalian virome” — or the collection of viruses found in mammalian bodies.
They simulated potential hotspots by using geographic models of the mammal virus network and range shift projections for more than 3,000 mammal species, under various climate change and land use scenarios for the year 2070.
A chief concern the scientists identified was the possibility that animal habitats will shift disproportionately to the same places that humans inhabit, amplifying the risk of viral spillover.
That process, they warned, is already underway in today’s environment, at 1.2 degrees Celsius (2.2 degrees Fahrenheit) above pre-industrial levels. And efforts to reduce greenhouse gas emissions may not be able to throw these events from unfolding, according to the authors.
Even if the world succeeds in keeping warming this century under 2 degrees Celsius (3.6 degrees Fahrenheit) — the internationally recognized upper limit for global warming — doing so “will not reduce future viral sharing,” the scientists noted.
Rising temperatures will have particularly worrisome effects on bats, as these winged mammals can both travel long distances and are responsible for the majority of novel viral sharing, according to the study.
The scientists projected that the greatest impacts of such viral emergence will occur in Southeast Asia, which they described as “a global hotspot of bat diversity.”
As viruses begin to jump between host species at unprecedented rates, the authors warned that the effects on both conservation and human health could be astounding.
“This mechanism adds yet another layer to how climate change will threaten human and animal health,” co-lead author Gregory Albery, a postdoctoral fellow in Georgetown University’s Department of Biology, said in a statement.
“It’s unclear exactly how these new viruses might affect the species involved, but it’s likely that many of them will translate to new conservation risks and fuel the emergence of novel outbreaks in humans,” Albery added.
While the authors concluded that climate change is poised to become “the biggest upstream risk factor for disease emergence” — surpassing deforestation, wildlife trade and industrial agriculture — they also pointed to a possible solution to this new predicament.
That solution, they contended, involves pairing wildlife disease surveillance with real-time studies of environmental change.
If a Brazilian free-tailed bat finds its way to Appalachia, for example, researchers should be looking into what viruses came along for the ride, Carlson explained.
“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,” he said.
“We’re closer to predicting and preventing the next pandemic than ever,” Carlson added. “This is a big step towards prediction — now we have to start working on the harder half of the problem.”