Healing forests

The forest-human health connection

Annika Terrana, WWF-US manager for forests, was studying abroad during college, focusing on environmental education and outreach with the Wildlife Clubs of Kenya, when she first made the connection between the environment and human health. “So much of the environmental degradation I saw was closely connected to obvious human well-being and poverty cycles,” she says. Later, working for a local nonprofit on the shores of Kenya’s Lake Victoria, she witnessed how the ongoing disruption of nature rippled through local communities, ultimately leading to subsequent threats of deforestation and the spread of infectious diseases like HIV and malaria.

Today, as the world reels from the COVID-19 pandemic and looks for solutions, it is vital that the underlying links between disease and deforestation be understood. 

For the past year and a half, Terrana has spearheaded the Forest team’s Forests and Health initiative in partnership with the world’s largest healthcare company, Johnson & Johnson. The three-year initiative aims to document how deforestation can undermine human health and economies, and how we can improve efforts to curb future disease outbreaks.

Terrana and her team are focusing initially on Sabah, Malaysia, a region where vast swaths of forests have been razed to make room for palm oil plantations, but also one that has recently made strong commitments to stopping deforestation. Ultimately, they hope to show how conservation of forests can serve as preventive medicine for us all—fostering proactive remedies to some of the world’s most pressing environmental and health concerns.

Ecosystems in chaos

Keeping forests intact protects biodiversity and the health of natural systems. But what exactly happens when existing forests are cut down to make way for products like palm oil?

“You take a system that has been woven together over millions of years of evolution to be a very complex integrated whole, and you rip it to pieces in a very short time,” says Samuel Myers, director of the Planetary Health Alliance and a principal research scientist at the Harvard T.H. Chan School of Public Health. In the process, he says, “you destroy a web of life and relationships that we don’t even begin to understand in terms of their complexity.”

Beyond the environmental wreckage, he says, are health consequences. “We know that, in most cases, when we impoverish the biodiversity in a system, we actually increase the risk of infectious disease exposures.”

“What society absorbs in terms of financial costs for public health crises is exponentially more costly than simply keeping forests intact.”

Annika Terrana
Manager, Forests, WWF-US

Deforestation is a key driver of that biodiversity loss. In 2019, the tropics lost close to 30 soccer fields’ worth of trees every single minute. A third of those were in primary, previously undisturbed rainforests. That rapid clearing of forests is drastically impacting the emergence of zoonotic infectious diseases, says Peter Daszak, president of EcoHealth Alliance, an organization that conducts research and outreach on emerging diseases and their underlying causes, and a frequent WWF collaborator.

How does this happen? “As you send people into forests, to build a road or do some logging, workers need food,” says Daszak. “Without a good food supply, they’re going to go get bush meat.” The consumption of wild meat is one risky interaction point where the transfer of disease from animal to human can take place.

Hunting—and the associated trade in live wild animals, often fueled by foreign demand— also puts humans in direct contact with wildlife and the pathogens that tag along for the ride. But “while diseases might be spread by wildlife trade,” Terrana says, “the enabling conditions can often be traced to tropical deforestation and habitat fragmentation.”

Infectious diseases can also be spread by vectors—the disease-spreading “middlemen” that can pass pathogens between species; often, the culprits are biting insects like mosquitoes. And many of those disease-carrying insects breed in puddles—the kind caused when deforestation disrupts waterways and carves shallow ruts into a scarred landscape, collecting rainwater in stagnant pools.

We already know that vector-borne diseases like Zika and dengue emerged from forests, carried by mosquitoes. As more land is cleared, different species of mosquitoes are exposed to humans in the fringe-forest areas—and new opportunities for disease transmission arise. 

The nexus of forests and health

For more than a century, scientists have been investigating the relationship between human and animal health and, more recently, between humans, animals, and the health and stability of the environment. Approaches to public health that take these interconnections into account are often referred to as planetary health approaches. WWF and Johnson & Johnson’s Forests and Health initiative takes the planetary health concept and pushes it a step further.

Terrana says Johnson & Johnson approached WWF to discuss where they might help with a project at the nexus of forests and health. The company has made commitments to sustainable sourcing of palm oil, but since they don’t source the oil directly, it’s proven difficult to verify practices all the way to the ground. “They wanted to support initiatives on the ground that demonstrate the value of healthy, intact forests and contribute to more responsible palm oil supply chains,” Terrana explains.

“Healthy people need a healthy planet. This is why we support efforts like WWF’s Forests and Health initiative that aim to advance cross-disciplinary solutions at the intersection of forest conservation and public health.”

Paulette Frank
Worldwide Vice President, Environmental Health, Safety & Sustainability, Johnson & Johnson

So the Forests and Health initiative team set out, with support from Johnson & Johnson and utilizing EcoHealth Alliance’s extensive research in Sabah, to connect the dots between forests and human health, and to clarify the role conservation could play. Currently, they are compiling existing research on forests, health, and conservation. Terrana says team members are trying to understand the level of degradation a forest can withstand before a cascade of negative and potentially irreversible consequences take effect.

Ultimately, they intend to provide the data to local businesses and governments to advocate for robust land-use policies and practices.

Inclusive solutions

Terrana stresses that if she and her team reach their goal of bringing together public health initiatives and conservation, it will create stronger communities. And by further untangling the complex connections between deforestation and human health in Sabah, the team wants to show how conservation can be a win-win for entire ecosystems and communities.

“What we’re trying to do is persuade policy-makers through the economics,” adds EcoHealth Alliance’s Daszak. “For example: If you cut down a forest and bring in a pig farm, you may make a profit, but you may also have diseases that will cost you for the next 50 to 100 years.” In essence, the short-term profits of habitat conversion will likely be eclipsed by related human health costs—problems that the host government has to pay for over many years.

“COVID-19 is a perfect example,” Terrana says. “What society absorbs in terms of financial costs for public health crises is exponentially more costly than simply keeping forests intact.”

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