Ed Yong writes:

For the world’s viruses, this is a time of unprecedented opportunity. An estimated 40,000 viruses lurk in the bodies of mammals, of which a quarter could conceivably infect humans. Most do not, because they have few chances to leap into our bodies. But those chances are growing. Earth’s changing climate is forcing animals to relocate to new habitats, in a bid to track their preferred environmental conditions. Species that have never coexisted will become neighbors, creating thousands of infectious meet-cutes in which viruses can spill over into unfamiliar hosts—and, eventually, into us. Many scientists have argued that climate change will make pandemics more likely, but a groundbreaking new analysis shows that this worrying future is already here, and will be difficult to address. The planetary network of viruses and wildlife “is rewiring itself right now,” Colin Carlson, a global-change biologist at Georgetown University, told me. And “while we thought we understood the rules of the game, again and again, reality sat us down and taught us: That’s not how biology works.”

In 2019, Carlson and his colleague Greg Albery began creating a massive simulation that maps the past, present, and future ranges of 3,100 mammal species, and predicts the likelihood of viral spillovers if those ranges overlap. The simulation strained a lot of computing power; “every time we turn it on, an angel dies,” Carlson told me. And the results, which have finally been published today, are disturbing. Even under the most optimistic climate scenarios, the coming decades will see roughly 300,000 first encounters between species that normally don’t interact, leading to about 15,000 spillovers wherein viruses enter naive hosts.

“It’s a little harrowing,” says Vineet Menachery, a virologist at the University of Texas Medical Branch. The study suggests that the alarming pace at which new or reemergent viruses have caused outbreaks in recent decades “is not some abnormal situation,” Menachery told me, “but what we should be expecting, maybe even with an acceleration.”

Carlson and Albery drolly nicknamed their study “Iceberg,” denoting a huge and mostly hidden threat that we unwittingly collide with. Indeed, their simulation revealed that mammalian viruses have already been dramatically reshuffled, to a degree that likely can’t be undone even if all carbon emissions cease tomorrow. The Anthropocene, an era defined by humanity’s power over Earth, is also an era defined by viruses’ power over us—a Pandemicene. “The moment to stop climate change from increasing viral transmission was 15 years ago,” Carlson said. “We’re in a world that’s 1.2 degrees warmer [than preindustrial levels], and there is no backpedaling. We have to prepare for more pandemics because of it.” [Continue reading…]