60 percent of new infectious diseases that emerge in people—including HIV, Ebola , and Nipah, all of which originated in forest-dwelling animals—are transmitted by a range of other animals, the vast majority of them wildlife.
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.”
In a complex analysis of satellite and health data published recently in the journal Proceedings of the National Academy of Sciences, MacDonald and Stanford University’s Erin Mordecai reported a significant impact of deforestation across the Amazon basin on malaria transmission, in line with some previous research. Between 2003 and 2015, on average, they estimated that a 10 percent yearly increase in forest loss led to a 3 percent rise in malaria cases.
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