The Environment

Environmental Change and Global Health Are Two Sides of the Same Coin

April 21, 2021  • Charles Minicucci

Although COVID-19 is still at full pandemic status in the US, it seems like the conversation is slowly shifting towards what happens next. SARS-CoV-2 may never be fully “eliminated,” but an aspirational view of recovery has started to take hold. Sometimes this manifests as a need for reflection—to ensure that the post-COVID future is indeed brighter.

Yet while the pandemic is certainly the loudest crisis facing the world right now, it isn’t the only one. Horrific wildfire seasons, record temperatures, and unprecedented weather events of recent years boggle the mind, but as America stares down the barrel of resurging infection waves, climate nihilism—or de-prioritization—is a natural stance to take. “What’s the point in trying to save the environment if some pandemic virus could wipe us all out tomorrow?” Over the last few months, I’ve heard this sentiment from peers more often than I can count. Usually it’s in reference to a failure to recycle the obscene amount of plastic packaging from one’s third takeout dinner of the week. Interestingly, the obverse has been similarly prevalent: “well, [insert impending climate crisis here] will happen soon anyway, so why should we be worrying about the next 100-year pandemic?”

The answer is simple: environmental protection is a matter of public health. And preventing the next pandemic is a matter of environmental security.

Here’s why. Those once-in-a-century diseases emerge from somewhere, and 60% of the time that somewhere is an animal population known as a zoonosis. The term zoonosis might conjure in your mind newsreels of Tyvek-clad veterinarians culling domestic turkeys and pigs to slow bird or swine flu outbreaks, but these pathogens did not arise in domestic animals. Livestock populations are often just the human-adjacent accelerant for an otherwise “wild” pathogen. Even measles and smallpox, diseases that we think of as endemic to humans, trace their evolutionary history back to animal origins. And scary pathogens are emerging much more often than once per century. The past few decades of unprecedented technological innovations in medicine have also seen unprecedented increases in zoonotic epidemic frequency (SARS, MERS, Ebola virus disease, Zika, the 2009 H1N1 pandemic, Nipah virus infection, COVID-19—just to name a few in my lifetime). Additionally, many of those zoonotic epidemic events can be easily traced to wildlife experiencing extreme environmental duress. Zoonosis prevention is, in fact, an ecosystem service.

Environmental considerations really start to play a role in zoonosis at the human-wildlife interface—and that interface is growing rapidly. The assumption that ‘the humans arrive and the wildlife leave’ isn’t exactly true. In the immortal words of Jeff Goldblum in Jurassic Park, “life finds a way”—and rarely does it find a way that bodes well for us. The underlying biological mechanisms of zoonoses haven’t changed; it’s still the accidental result of a genetic lottery that enables a pathogen to adapt to a new host. But the more humans come in contact with wildlife, the more times we’re effectively rolling the dice. As human population centers expand and natural wildlife habitats vanish, the animal species that win out are those that can most easily adapt to the new human-dominated landscape. Those species that thrive in anthropogenic or human-created ecological niches are also ones that account for the majority of zoonotic diseases: primates, bats, and rodents. This reduced biodiversity in the face of dramatic land-use change usually results in one of two eventualities: either the remaining species outcompete others and explode in number by nestling up close to humans (think: rats in the sewers and bats in the belfries); or, surviving species wind up stressed, bottlenecked, and less genetically diverse—making them much less capable of weeding out infections within their own population before encountering humans and passing them on (think: foxes contracting rabies).

It is impossible to ignore the interconnectedness of public health and environmental security.

It’s all too easy to think of infectious disease outbreaks as unpredictable natural disasters, but some predictive capacity does exist. In the same way that meteorologists can predict low-pressure systems, the theoretical knowledge to give us a fighting chance against the next pandemic already exists. Disease ecologists know some species are likely to harbor pathogens with zoonotic potential, and they can find out where and when they frequently come in contact with humans. We know which latitudes and elevations are likely to see changes in temperature and precipitation that will provide fertile new ground for disease-carrying mosquitoes.

So we know how to begin forecasting zoonoses or anticipating the shifting maps for vector-borne illnesses—in fact, some groups like the USAID PREDICT project, the Cary Institute, and EcoHealth Alliance have already started doing it. The obstacles lie in the untapped potential of interdisciplinary collaboration. Effective GIS models and predictive disease mapping require talented mathematicians and software engineers. Viral metagenomics on the scale required to effectively surveil the zoonotic reservoirs that we know of requires an incredible application of molecular biology and data science. And the data-sharing required to combat outbreaks that know no borders will demand immense feats of international policy.

The point here is not to stack more problems atop the ever-growing list; it’s to consolidate these pressing needs under a single manageable heading: One Health. If we address the needs for zoonosis prevention as a combined issue with a fully-articulated, well-understood network of interactions, then suddenly it could feel like we’re all cooperating and collaborating to solve one, multi-faceted issue instead of further restricting our lanes of expertise and responsibility into narrower and narrower specialties.

Ultimately, it’s not just zoonoses we need to be worried about. Environmental considerations touch on many other aspects of infectious disease: farming and mining practices create habitats for waterborne parasites, ecological disturbances enhance growth and spread of vector-borne diseases such as ticks, severe outbreaks of seasonal influenza is tightly correlated with milder winters over the past 25 years. The predicted 2-5°C rise in global temperatures will put an estimated 500 million to 1 billion people at risk of mosquito-borne illnesses they’ve never before been exposed to. When you factor in non-communicable diseases and the socioeconomic determinants of health that climatic shifts have already begun to exacerbate, we start to glimpse the universality of the issue. The list goes on and on until eventually, it’s impossible to ignore the interconnectedness of public health and environmental security.

It will take epidemiologists, veterinarians, agricultural engineers, geographers, mathematicians, conservation biologists, policymakers, environmental regulators, sociologists, behavioral scientists, resource managers, and more all working together to predict and prevent pandemics, alleviate the effects of environmental change on human and veterinary health, and restore integrity to our ecosystem services. We cannot recover from COVID-19 or prepare for an unknown Disease X in a resilient, equitable way without addressing climate. And we’ll never bring to bear all the necessary resources to combat environmental change without addressing emerging infectious diseases as a deeply connected issue.

Charlie Minicucci is a research assistant at the National Academies of Science, Engineering, and Medicine. He works on issues in global health with NASEM’s Forum on Microbial Threats and One Health Action Collaborative.

The author is solely responsible for the content of this article, which does not necessarily represent the views of the National Academies of Science, Engineering, and Medicine or the Aspen Institute.

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