(Bloomberg) -- In the 20th century, public-health victories saved people’s lives and livelihoods from both ancient scourges and industrial-era dangers.

The 21st century is all about preparing for new kinds of events—many relaed to climate change—that we need to plan for ahead of time, even though we have never experienced them before.

The great contagions of the early 1900s catalyzed modern public-health infrastructure. The 1918 flu eventually led the U.S. to organize the National Institutes of Health. The U.S. military’s WWII anti-malarial program morphed into the CDC (then called the Communicable Disease Center) in 1946. Two years later, the brand-new United Nations founded the World Health Organization to organize global fights against transmissible diseases.

By the turn of the century, these developments contributed to an astonishing top-line benefit: U.S. life expectancy at birth rose 62%, to 76.8 years, from 47.3 years in 1900. Along the way, vaccines eliminated smallpox and polio, and nearly banished mumps, measles, rubella and whooping cough. Improved sanitation and cleaner water washed out infectious diseases like cholera. Cars, workplaces and food all became safer.

So, what would a list of century-long public-health victories look like in 2099?

Researchers have dedicated much time and resources to the century’s newest, and many say biggest, health threat: climate change. These experts have raised alarm at how fast the world is falling behind in its ability to face threats and diseases emerging from the ravaged natural world.

“The challenges that are facing the health profession and public health are coming from outside of the health sector,” said Nick Watts, executive director of the Institute for Global Health at University College London and lead author of a comprehensive 2019 study of climate change and public health in the Lancet. Medical professionals and institutions are prepared to respond to known threats, not the unknown.

Watts and his team catalogued an array of crises that might appear on a 2099 public-health victory list: heat, wildfires, lethal weather, air pollution and more. To beat them, Watts said that the entire health system may find it productive to move toward preventative care, wherever possible, aided by virtual medicine. 

“We had assumed that the environment was going to stay the same because the environment used to stay the same," Watts said. “We didn’t quite appreciate the importance of all of the benefits you get from a stable climate until it started to change.”

The problem is no longer theoretical. Past climate-related events have already harmed public health. During Europe’s historic 2003 heatwave, for example, 70,000 people died. Just like the current coronavirus pandemic, not all those deaths were due to the heat itself. “They died because the health system was overwhelmed,” Watts said. “It’s a very, very similar story to what we’re seeing in Italy.”

Environmental degradation has already been identified as a cause of the Covid-19 pandemic. China’s wildlife markets—where both live and dead animals are bought and sold in tight quarters—likely allowed viruses to mix across species, creating conditions “ripe for new emerging agents of disease, like Covid-19,” said Jonathan Patz, director of the Global Health Institute at the University of Wisconsin-Madison. 

Unlike measles or polio, there is no vaccine for ecosystem destruction. As Patz and colleagues wrote in a 2004 Environmental Health Perspectives paper, “Human-induced land use changes are the primary drivers of a range of infectious disease outbreaks” and the emergence of new epidemics.

Once the Covid-19 emergency ends, the global public health community and world population that depends on it will have to finally face the 21st century’s biggest challenge: The most dangerously ill patient of all may be the planet we inhabit.

Eric Roston writes the Climate Report newsletter about the impact of global warming. Sign up to receive the Green Daily newsletter in your inbox every weekday.

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