In the early 1990s, Kinari Webb took a year off college to join a Harvard researcher studying orangutans in Indonesia’s rainforested Gunung Palung National Park. As the aspiring primatologist dissected dung samples to determine the animals’ feeding habits, the buzz of chainsaws and the thwuuuump of falling dipterocarp trees—some of the tallest species in the world, routinely rising more than 200 feet—broke through the great apes’ calls. Despite federal protection for the land, loggers illegally, and extensively, felled trees throughout the preserve, which sits on the western coast of Borneo. In fact, some of the local research assistants who helped Webb’s team uncover scat were former loggers, including a man named Tadyn (like most natives, he does not use a surname). One day, he came to her with a gaping cut in his hand, surprisingly distraught for someone who had once fought an attacking sun bear—and won. “It wasn’t that big of a wound,” Webb recalls. “His machete had slipped. But he had terror in his eyes, the most I’ve ever seen in a person.”
For locals, a minor injury could be life-threatening. They didn’t have access to tetanus shots or antibiotics, and getting to the nearest hospital entailed a day’s journey by dugout canoe, followed by another on a motorboat and another in a car. Accessing treatment incurred costs that were astronomical relative to their incomes, so, around Gunung Palung, medical emergencies brought out the chainsaws. Because the protected areas are off-limits to the wide-scale clearing that has created lucrative palm oil plantations across Borneo, villagers often cut and sell the virgin trees. One resident Webb met downed 60 to pay for a relative’s cesarean section. As Tadyn told her, “We don’t have any other choice.”
As she continued her work in the Bornean forests in the intervening decades, Webb would discover another consequence of the tree-chopping economy: Pervasive illegal logging can also threaten public health. Disease ecologists increasingly agree that human disturbance of wildlands increases the risk of zoonotic diseases—pathogens that jump from animals to people—which helps explain why spillover events, as epidemiologists call them, are on the rise around the globe. The number of fauna-borne outbreaks quadrupled between 1980 and 2010, according to a 2014 analysis from Brown University, and the Centers for Disease Control and Prevention says that three-quarters of human illnesses discovered in recent decades originated in wildlife. The US Agency for International Development’s PREDICT program estimates that animals harbor some 700,000 as-yet-unidentified infectious baddies with the potential to make the jump to people. It takes only one of those to change the world.
We’ve traded pathogens with other creatures for millennia, but in the past, if an outbreak did occur, geographic spread was limited. Not so in the era of globalization and population booms. Ecological disturbance—whether from deforestation, natural disasters, or climate change—often puts both people and animals on the move. Species that were not typically in contact with one another may suddenly find themselves in close proximity and sharing pathogens.
Consider the Black Death, which in the 1300s killed up to half of Europe. In 1925, Malaysian physician Wu Lien-Teh confirmed the source of the infamous disease—fleas in the fur of Central Asian rodents called tarbagans—which enabled later generations of scientists to unravel the social and environmental factors that conspired to spread the deadly illness. The advent of agriculture in the region offered an ample food supply, spurring a spike in the rodents’ population; demand for their furs made the creatures a lucrative target for hunters; and trade along the Silk Road eventually brought the plague to Europe.
More recent zoonotic spillover events—including AIDS, Ebola, MERS, and SARS—have followed a similar pattern, and COVID-19′s story comes from the same playbook. Some epidemiologists suspect that horseshoe bats passed SARS-CoV-2, the virus that causes the illness, to Sunda pangolins, armadillo-like creatures poached in Southeast Asian countries and sold live in markets in the now-infamous Hubei province, before the disease was ultimately transmitted to us. Brazilian biologist Gabriel Laporta was among the first to suggest that deforestation may have driven the bats and pangolins to nest in the same caves—a novel opportunity for the coronavirus to hop species.
Webb doesn’t know what unknown diseases might be lurking in the forests of Borneo (Nipah virus, which inspired the movie Contagion, hails from the region), but she has spent much of her career developing a unique conservation model that may keep zoonotic bugs in the shadows, rather than boarding planes. Her goal is to help local communities avoid risky practices surrounding logging, such as eating wild animals (often referred to by Westerners as bushmeat).
This mindset puts Webb squarely within the emerging field of planetary health, an interdisciplinary movement of scientists who view the destruction of the environment as a top public health threat. “We need to think differently about how we manage our interface with wildlife,” says Samuel Myers, director of the Planetary Health Alliance, a consortium of more than 200 universities, NGOs, research institutes, and government entities. People, he says, often intrude into habitats because “they’re trying to feed their families, so we need to give them an alternative.”
Webb helps form the front line of pandemic prevention. After her aha moment with Tadyn (who recovered after a little first aid), she dropped primatology and pursued a medical degree at Yale, eventually returning to Borneo to address rainforest conservation through a program that integrates sustainable agriculture, reforestation, and health care into an anti-logging economy. In 2007, she founded Alam Sehat Lestari or ASRI (loosely translated: Healthy Nature Everlasting), a nonprofit that operates clinics in villages flanking Gunung Palung and Bukit Baka Bukit Raya national parks. (Webb is also midwifing similar programs in other rainforested regions around the globe.) With philanthropic backing from entities like the Disney Conservation Fund, the facilities offer a sliding price scale for their services based on an individual’s logging practices, or lack thereof; the latter qualifies for 70 percent off. The organization also offers a chainsaw buyback program and organic farming training, a popular initiative that has helped buoy incomes, further reducing the temptation to cut down trees.
In ASRI’s first decade of operation, the number of households that log in the surrounding land dropped by nearly 90 percent, 52,000 acres of Gunung Palung forest regrew, and infant mortality fell by two-thirds. The 122,000 residents in ASRI’s service areas now have access to a level of care largely unheard of in such remote locales—all the more essential once COVID-19 entered the region.
Epidemiologists have long noted a correlation between habitat loss and outbreaks of infectious diseases, from the plague-dispersing tarbagans to malaria-carrying Anopheles mosquitoes, warmth-loving insects that proliferate when tropical forests are reduced to denuded land pocked with mud-puddle breeding grounds. In the 1930s, parasitologist Yevgeny Pavlovsky introduced the idea that spillover events are defined not just by biological forces but also by ecological ones, a theory informed by his decades of fieldwork studying illness-spreading lice and ticks in the Soviet hinterlands.
Ecological change, however, often comes as a result of social and economic catalysts. In the 1950s, American public health pioneers Hugh Leavell and E. Gurney Clark popularized the “epidemiological triad” model of infectious disease: A pathogen, its host, and the environment in which they come together dictate the severity of an outbreak. The pair considered a pathogen’s circumstances in broad terms—ecological, cultural (e.g., wild game consumption), and political (e.g., conspiracy theorists). They argued in their 1953 Textbook of Preventive Medicine that addressing the environmental arm, the part humans can control, was necessary “to intercept the causes of disease before they involve man.”
Since then, the link between human-made environmental changes and outbreaks has been increasingly well documented. In the 1990s, wife-and-husband ecologists Felicia Keesing and Richard Ostfeld began studying the dynamics of Lyme disease in the northeastern United States. Based, respectively, at Bard College and the Cary Institute of Ecosystem Studies in the Hudson Valley—an area north of New York City known for its bucolic farms, vineyards, and escaping urbanites—the pair found that as forests gave way to McMansions, predators like snakes, owls, and foxes suffered steep declines and failed to keep white-footed mice, the critters that ferry Lyme-carrying ticks, in check.
These so-called weedy species proliferate in upended areas. “When we fragment or degrade or destroy habitat,” Ostfeld says, “we are essentially applying a filter where we’re getting rid of the species that help suppress pathogens and favoring those that tend to be good amplifiers.” Confirmed cases of Lyme in the US have doubled since the ’90s, when housing developments increasingly encroached into rural areas and created patchy forest remnants. In a 2003 study in Conservation Biology, Keesing and Ostfeld found that the risk of exposure to Lyme increases fivefold when canopied areas cover less than five acres.
Low biodiversity has led to numerous other outbreaks, including instances of hantavirus, Lassa fever, leishmaniasis, and West Nile virus. (In the last case, important vectors include invasive, opportunistic species, such as European house sparrows, that proliferate in urban landscapes at the expense of less adaptable native birds.) Conversely, higher biodiversity helps dilute threats by ensuring an abundance of predators keep populations of weedy species in check, and thus help slow the spread of disease.
This picture is complex, and largely incomplete. But as David Quammen, author of Spillover: Animal Infections and the Next Human Pandemic, writes, the take-home is simple: “Ecological disturbance causes diseases to emerge. Shake a tree, and things fall out.”
Quammen provides an apt visual for the Nipah virus epidemic that emerged in Southeast Asia in 1998, one of the best-documented cases of “tree shaking” leading directly to an outbreak. Malaysian microbiologists traced the disease to flying foxes (bats that look like small dogs with the wingspans of eagles) on Tioman Island, across the South China Sea from Borneo. Habitat destruction to clear land for palm oil plantations, exacerbated by El Niño–induced drought, caused the bats to migrate out of the forests and forage near industrial pig farms. They gathered food in fruit trees above the pens, and the swine gulped down the guano and infected bits of grub that rained from above. Soon farmhands and slaughterhouse workers were showing up at emergency rooms in Nipah-induced deliriums. The disease swept through the region with a fatality rate of up to 40 percent, killing more than 100. Of all cross-species interactions, sharing food with wildlife—or, worse, eating wildlife—provides pathogens with some of the best opportunities to spill over.
During her sojourn in Gunung Palung National Park as an undergrad, Webb began to witness firsthand a pathway for zoonotic transfer. Her primary task was to study how orangutan digestion helps Bornean trees germinate. (She spent her days fishing fruit seeds out of dung.) But illegal logging and the conversion of rainforest to palm oil plantations and other agriculture left the majestic primates critically endangered, in turn making any Homo sapiens presence most unwelcome to the great apes. “They do not like humans,” says Webb. “They would break off branches and throw them at us.” In Bukit Baka Bukit Raya National Park, where Webb later worked, she learned why: The villagers, she says, “had eaten nearly all the orangutans.”
There, the local Dayak tribes, like many indigenous groups around the world, historically subsisted on wild game, including primates, bats, and rodents—three groups of mammals epidemiologists say are prone to harboring diseases capable of attacking a human host. But these days such eating habits among the Dayak largely occur only when they’re away from home, says Webb. “It happens mainly when they’re logging: They go into the forest for weeks at a time, and they have to eat, so they hunt. It’s dangerous.”
When Webb founded ASRI in 2007, she began with a series of community meetings in the 44 villages surrounding Gunung Palung. “You are guardians of this precious rainforest that is valuable to the whole world,” Webb said to the Borneans. “What do you need as a thank-you from the world so that you can protect it?” The same two answers came up again and again. The first was access to affordable health care, a confirmation of her aha moment with Tadyn. The second? Training in organic farming.
For locals, the chemical-free approach was a practical matter, not some groovy plan to save the planet. The Indonesian government had long promoted modern rice farming in the area, which requires expensive fertilizers and pesticides that left cultivators in debt—another incentive to keep logging. “They had heard that people in other places knew how to plant without chemicals,” says Webb, so she promptly hired an organic farmer from neighboring Java to train them.
Borneans have a tradition of slash-and-burn agriculture. As crops deplete the soil of nutrients, villagers constantly clear new plots of land. But the Javanese traditionally grow in one place year after year by enriching the earth with compost and cover crops that add nitrogen. Slash-and-burn was sustainable when populations were smaller and other pressures on the forest fewer, but in modern times it’s an ecological disaster. “They said, ‘It isn’t working for us anymore, we know we have to shift,’” Webb recalls.
At ASRI headquarters in Sukadana, the largest town in the vicinity of Gunung Palung, Jilli, the organization’s sustainable agriculture coordinator, walks barefoot past plantings of dragon fruit, bitter melon, and tomatoes propped up on a makeshift bamboo trellis. In an open-air shed, a device that resembles a pint-size rocket ship cobbled together with steel drums transforms coconut husks into a concentrated black liquid that, when sprayed on plants, helps keep pests at bay. In this demonstration garden, Jilli coaches the 17 organic farming cooperatives that have sprung up in the area since ASRI started its training program in 2008; those plots now supply about 70 percent of the produce available in local markets.
Like many of the farmers, Jilli’s a former logger. “We try to convince our friends to transition to farming,” he says through a translator. He sports a T‑shirt reading “Bertani Organik—Sehat, sejahtera” (Organic Farming—Healthy and wealthy).
Jilli’s garden lies behind ASRI’s sprawling health clinic, a cluster of airy, white buildings linked by a covered walkway. Built in 2015, it feels more like a tranquil jungle lodge than medical offices, but with 20 beds for overnight stays and facilities for childbirth and minor surgeries, it’s the closest thing to a hospital in Sukadana. Green and purple scrubs dry on a clothesline. One building is now an isolation ward.
Hendriandi, ASRI’s reforestation coordinator and one of the few COVID-19 patients in the region to date, tends native syzygium seedlings in the nursery next to Jilli’s garden. The organization pays local crews, including many former loggers, to plant the trees. Since 2007, they’ve put more than 200,000 into the ground, including many of the fruiting species like durian that orangutans adore.
The three threads of ASRI’s program—health care, organic farming, and tree planting—interweave in a single conservation economy. Febriani, ASRI’s executive director, approaches the cashier window to demonstrate how it works. Villagers who have given up logging (as verified by on-the-ground observation by a team of “forest guardians”) receive a discount on health services; for the remainder of the bill, she says, with a wry grin, ASRI accepts a variety of alternative currencies: manure, tree seedlings, handicrafts, labor, and other noncash payments. A sign on the wall shows the conversion rate between Indonesian rupiah and various goods and services. Manure, for instance, nets 700 rupiah (about 5 cents) per kilo. In 2019, villagers cashed in a total of 23,000 seedlings as payment, which supplied reforestation efforts. “The rarest species are worth the most,” Febriani says.
Webb points out that the system makes the interconnectedness between health and the environment plain to the members of the community. “You can see it: I’m paying with seedlings because healthy forests lead to healthy people,” she says. “I’m paying with manure because manure can be used for organic farming, which is healthier for humans and for the planet.”
Pandemic prevention joins a mountain of good reasons to leave nature alone. Yet balancing conservation with population growth remains a challenge. Webb believes she’s hit upon a viable model, and she’s attempting to scale it up. In Borneo, she has a discount program in the works for families who forest guardians can confirm have stopped hunting protected species. And the program’s reach can cross borders: A lack of affordable health care drives destruction of habitats in rainforest communities everywhere, she says. Already ASRI has more than 100 employees in Indonesia (twice that number in tree-planting season), and Webb has recently established a similar program in Madagascar and is launching another one in the Amazon.
Her team is one of many working across the globe on interdisciplinary efforts considered part of the field of planetary health. An initiative in Senegal, for example, will reintroduce edible native river prawns that prey on the snails that transmit the parasitic flatworm that causes schistosomiasis.
ASRI, says Planetary Health Alliance head Myers, “is a fantastic example of how to prevent the incursions into wildlife habitat that are at the heart of a lot of emerging infectious disease.” The question, in his mind, is whether its model can be sufficiently scaled. “We need to be doing this in 10 million villages.” That degree of growth demands buy-in from governments.
A fiscal analysis published in Science in July 2020 put the global investment needed to reduce zoonotic disease risk at about $30 billion per year—a pittance compared to the estimated damage from COVID-19, which ranges from $3 to $80 trillion over the next five years. The paper addresses forest conservation and measures to reduce wildlife trafficking, as well as medical and technological solutions. In Brazil, for instance, an app allows residents to report dead and afflicted fauna in hopes of identifying emerging outbreaks.
For decades, many have been ignorant of the connection between ecosystem health and infectious disease. Now, with COVID-19, more people are connecting the dots. “Part of our messaging right now is, ‘Hey, guys, you know how we’ve been telling you it’s not such a good idea to eat wild animals? Here’s some proof,’” says Webb, before recalling a soundbyte from director Febriani: “COVID-19 is a symptom of a sick planet. Planetary health is the cure.”
Hamisah, an ASRI health-care worker and chief of a nearby village (the first woman to hold the distinction in the region), has never traveled farther than the overnight trek to Jakarta, but fully understands that her community’s actions can have global implications. “When the wildlife have to go out of the forest, there’s a risk of transferring disease to humans,” she says, sitting on the floor of a medical storeroom, face mask looped around her neck. “If they are safe there and have things to eat, it’s safer for us.”
This article was produced in collaboration with the Food & Environment Reporting Network, an independent, nonprofit news organization.
This story appears in the Winter 2020, Transformation issue of Popular Science.