The Climate-COVID Connection
Understanding the links between environmental change and public health is essential for creating effective solutions
Lemurs are cute. For more than half of northeastern Madagascar’s rural Malagasy people, they’re also dinner. Once abundant, most of the 101 species of these primates are now critically endangered. Many members of the rapidly growing Malagasy population—driven by extreme poverty and food insecurity—overhunt, depleting a food source people have relied on for generations. They also clear trees to grow crops, eliminating lemur habitat and forests that provide planet-sustaining carbon sequestration.
Well-meaning conservation acts and hunting bans aimed at preserving biodiversity haven’t addressed the social drivers of this cycle. “Conservation efforts without considerations for how the Malagasy were actually using the forest appeared futile,” says Christopher Golden (MPH ’10; PhD ’11 Environmental Science, Policy, and Management), an assistant professor of nutrition and planetary health at Harvard.
Madagascar epitomizes how climate change, human health, and social conditions interact on the ground. Rausser College of Natural Resources researchers have long studied this nexus, but the coronavirus pandemic—with its worldwide economic and human-health tolls—has laid bare the relationships for everyone to see. Social factors like poverty and urbanization change land use, which shifts biodiversity and animal habitats. In turn, increased contact between wild animals and people creates more opportunities for zoonotic diseases—those that jump from animal hosts to humans—to spread. The coronavirus that causes COVID-19 was one such opportunistic virus, which scientists believe came from a bat.
These systemic problems require interdisciplinary solutions. The good news is that Rausser researchers have been formulating such solutions for decades. The most sustainable of these share the premise that climate change, emerging disease, and social equity cannot be disentangled.
Sustainable food, sustainable forests
The term “zoonotic disease” may not be widely known, but the epidemics caused by crossover into humans—such as COVID-19, Ebola, AIDS, Zika, and West Nile fever—are household names. More than half of the emerging diseases worldwide are caused by these crossover events.
Golden has been studying the environment-health-culture nexus in Madagascar for two decades, working with Malagasy communities to develop a sustainable protein source as an alternative to lemurs and other bushmeat.
“Chicken was the top taste preference,” he says, citing the findings from a study in which he analyzed 31 meats. Chicken skirted local cultural taboos that disqualified many other options. And, he notes, women typically manage poultry production. “We know that when women have control over an asset, it tends to be used in beneficial ways,” he says—for the family’s food, health care, and education. Critically, Golden spent years developing vaccination and training programs to mitigate a flock-decimating bird blight that had upended local chicken-raising efforts.
His innovations are now making poultry an economically viable choice, judging by early anecdotal reports, which show increased chicken consumption and reduced hunting. Golden hopes to eventually see benefits on all fronts: decreased animal-human contacts, less forest destruction, and improved nutrition and food security for the Malagasy.
“Pairing conservation and development initiatives together supports local people’s needs,” he says, “particularly when wild food sources are unsustainable and even more so when they’re likely disease reservoirs.”
Keeping animals and habitats healthy
Bats are particularly active disease reservoirs, according to Cara Brook, a Miller Institute postdoctoral fellow working with the labs of Britt Glaunsinger and Mike Boots. Brook has collaborated with Golden on lemur studies, but her specialty is bat-borne zoonotic disease.
Modeling of infectious-disease transmission uses three factors, she explains: the infectiousness of the disease-carrying host, the susceptibility of the recipient host, and how often the two come into contact. “Any lever that pushes and pulls on those three components impacts the transmission rate,” she says.
Live-animal markets, for example, pull two levers. They create frequent animal-human contacts, and the stressful market environment—stacked cages—makes the animals more infectious. “Animals tend to shed more virus in the same way that humans who host herpes viruses do: we get cold sores when we’re immunocompromised,” Brook says.
Likewise, the stress of malnourishment makes bats more infectious, and when habitat shifts like deforestation bring them closer to people, transmissibility goes up. Brook works with Bat OneHealth, an international group of zoonotic-disease researchers who study bat-human contact at sites worldwide, including near Brisbane, Australia, where fruit bats have been roosting in downtown parks and shedding the lethal Hendra virus.
In a pilot project, Bat OneHealth scientists are replanting bat roosting and feeding habitats to improve the animals’ nutrition and draw them back into the forest—and away from people. Tree planting mitigates both climate warming and disease risk. “That’s a way that improved conservation of forest resources for these animals can also reduce greenhouse gases, a win-win,” Brook says.
Understanding disease-vector changes
Valeri Vasquez (MS ’18 Energy and Resources Group), an ERG doctoral candidate, is using computational models to research how genetic technologies might work as public health interventions. “We’ve had pandemics before; what we haven’t had is access to this volume of data,” says Vasquez, who spent five years working in the Office of the Special Envoy for Climate Change in the Obama administration’s State Department. Her models help scientists explore how disease vectors like mosquitoes will react to climate change and how methods to control them—for example, gene-editing or sterilization techniques—may need to shift accordingly.
Vasquez’s dissertation comprises case studies related to malaria, dengue, and other mosquito-transmitted diseases. As global warming shifts precipitation patterns, mosquitoes are moving. “Are we going to see more or less malaria, or might it start surfacing in new geographic areas?” she asks.
If scientists can better understand how disease vectors might adapt to climate change, more-effective preventative measures can be taken.
In the United States, ESPM professor Rachel Morello-Frosch (BS ’88, MPH ’93, PhD ’97) has spent her career focusing on communities that are the most vulnerable to health impacts from climate change.
“From a biological standpoint, viruses don’t discriminate,” says Morello-Frosch, who is also a professor in the School of Public Health. “But COVID-19 has shown us how racial inequality, climate change, and public health are intimately connected—for instance, how inequality and structural racism result in COVID’s disproportionate impact on African American, Latino, and Indigenous communities.”
America’s racialized division of labor is partly to blame, she says. People of color and those living in poverty are more likely to hold such “essential occupations” as grocery clerk, farmworker, or home health aide—jobs that tend to increase virus-exposure risk while providing limited health care coverage. These same communities have a higher prevalence of underlying health conditions—cardiovascular disease, diabetes, asthma—that exacerbate COVID-19’s impacts. And they are often located in neighborhoods with higher air-pollution exposure, which, research shows, damages the respiratory system and can lead to COVID-19’s worst outcomes.
Morello-Frosch says that understanding these linkages provides opportunities for change. As California updates the climate goals first laid out in Assembly Bill 32—at the time of its enactment, the most ambitious climate-change policy in the nation—it’s simultaneously lowering greenhouse gas emissions and strengthening public health. For example, California’s Community Air Protection Program, part of Assembly Bill 617, funds local air-quality monitoring and action plans to reduce pollution emissions.
“There are huge opportunities for short-term public health benefits, because with every ton of greenhouse gas emitted, there are also co-pollutants, like particulate matter, that affect health right now,” Morello-Frosch says. One of her recent California studies documented a corresponding 2 percent decrease in preterm-birth rates within two years of nearby power plant closures. “To put that in perspective, if we invented a drug that reduced preterm-birth rates by 2 percent, it would be considered a blockbuster.”
Clearing the air
As the country struggles to get back to normal, Morello-Frosch hears more conversations about the intersection of social and environmental justice. The phrase “I can’t breathe” has become connective tissue, she notes. George Floyd’s tragic plea is a metaphor for police violence against Black and Brown people, but it also conjures the hallmark symptom of the sickest COVID-19 patients and evokes the respiratory impacts of living in polluted areas—even without the smoky air of climate-change-driven, high-intensity fire seasons.
“Our country needs to keep making these connections between justice, sustainability, and equity as we forge our economic recovery,” she says. “A recovery strategy has to provide economic and climate-mitigation opportunities that protect the most vulnerable among us.”
Vasquez, whose Obama administration work led up to the Paris climate agreement, has participated in such policy deals on a global scale. She says that as researchers develop policy recommendations, human factors like popular will and empathy are just as important as the science.
“As scientists, we sometimes think, ‘I just need to explain it better.’ But with COVID-19, we’re seeing the need to tap into empathy, into people’s willingness to care about others,” she says. “You have to meet people where they are, in the contexts in which they have lived their lives.”
During the pandemic, our faculty, students, and alumni play a critical role by offering expertise in public health, epidemiology, infectious disease, virology, ecology, policy, economics, law, and other fields. Visit our website for a sampling of Rausser College research, commentary, videos, and other resources that relate to the coronavirus.