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Field Notes

How Protecting Habitats Could Help Prevent Future Pandemics

Wildlife health is not separate from our own. To forestall new infectious "spillover" events, experts are looking to familiar conservation tools.

Amid all the uncertainty today, one thing is sure: This will not be the last pandemic. New infectious diseases are jumping from animals to humans at an accelerating pace. Experts suspect that Ebola, HIV, MERS, and the new novel coronavirus all emerged this way. Other plagues wait in the wings: About half of an estimated 1.7 million unknown viruses that infect mammals and birds might possibly infect people—with unpredictable consequences.

Many officials have called for outlawing wildlife markets and trade to prevent outbreaks, and China has taken short-term measures in recent months. But that’s an imperfect solution; such bans hit poor people hard and can drive activity underground. Besides, they address only one of many situations that bring people and wild animals together.

As conservationists point out, infectious “spillovers” are especially likely in places where people cut down forest for farming, logging, grazing, or roadbuilding. Such landscape changes may bring humans closer to animals they once rarely encountered, or transform the habits and mix of species in ways that spread infections. Wild animals that are declining specifically because of habitat loss share twice as many viruses with people, according to research from PREDICT, an emerging pandemic threats monitoring program funded by USAID.

“The same things causing species to decline are causing public health risks,” says the program’s director, Christine Kreuder Johnson, an epidemiologist and veterinarian at the University of California, Davis School of Veterinary Medicine.

Johnson and a small cadre of like-minded experts around the world are working to integrate human health, animal health, and environmental policy. Their hope is that protecting ecosystems may actually help prevent pandemics. However, this equation is not nearly as simple as it sounds: Just as doctors don’t treat all diseases with the same medicine, ecological interventions would need to be fine-tuned to reduce a specific threat of infection. “It’s not going to be an easy answer like: Conserve biodiversity, period,” says Stanford University disease ecologist and veterinarian Susanne Sokolow.

Few systems are studied deeply enough to pinpoint how spillover occurs, but research in Australia offers one example. Decades of work showed that deforestation there has led flying foxes to congregate in urban trees, where they pass Hendra virus to horses—which can in turn pass it to humans. To help minimize this risk, Montana State University disease ecologist Raina Plowright has developed a project to restore native flowering trees that can lure the nectar-eating bats back into forests.

A more preliminary study comes from near Uganda’s Kibale National Park, where farms border tracts of remnant forest. Models suggest diseases are especially likely to make a leap in these patchy regions. Stanford medical and doctoral student Laura Bloomfield recently found that people often interact with primates when they enter the forest in search of building materials. Her data suggest providing people with lumber or creating forested buffer zones might help.

Yet another proposal, this one in the exploratory stage, targets Sin Nombre, a hantavirus carried by deer mice that can be fatal to humans. The idea: Build nest boxes for barn owls, since a family can devour about 1500 rodents per year. Further research is needed, however, to confirm its effectiveness and that it won’t backfire by, for instance, increasing transmission among stressed-out mice.

Most public health officials aren’t thinking about ecosystem management quite yet. “If there’s a recognition that human health and environmental health are interdependent, and if that turns into something that helps us increase conservation efforts, that would be so wonderful,” says Suzan Murray, program director for the Smithsonian’s Global Health Program.

The pandemic’s catastrophic human and economic toll could consign such plans to the back burner—or provide new urgency, Murray adds. “I hope this time brings out a lot of those ideas, where we understand how dependent we are on the natural world,” says Johnson. “It’s past time.”

This story originally ran in the Summer 2020 issue as “Wildlife Health Is Not Separate from Our Own.”​ To receive our print magazine, become a member by making a donation today.​

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