National Geographic reports that as more and more forest is cleared around the world, scientists fear that the next deadly pandemic could emerge from what lives within them.

Over the past two decades, a growing body of scientific evidence suggests that deforestation, by triggering a complex cascade of events, creates the conditions for a range of deadly pathogens—such as Nipah and Lassa viruses, and the parasites that cause malaria and Lyme disease—to spread to people.

As widespread burning continues today in tropical forests in the Amazon, and some parts of Africa and Southeast Asia, experts have expressed concern about the health of people living at the frontiers of deforestation. They’re also afraid that the next serious pandemic could emerge from our world’s forests.

“It’s pretty well established that deforestation can be a strong driver of infectious disease transmission,” says Andy MacDonald, a disease ecologist at the Earth Research Institute of the University of California, Santa Barbara. “It’s a numbers game: The more we degrade and clear forest habitats, the more likely it is that we’re going to find ourselves in these situations where epidemics of infectious diseases occur.”

Get the full story at nationalgeographic.com.