“I think…I think that’s unfathomable, frankly,” Morrison said. 

Morrison wasn’t the only one. As a suspected primary source for the spread of COVID-19 in late 2019, China’s wet markets—in which butchers sell meat from domesticated and wild animals—are, for many, a clear target for permanent closure. 

“We need to protect the world against potential sources of outbreaks of these types of viruses,” Morrison said. “It’s happened too many times.”

But according to scientists who’ve been studying coronavirus-type outbreaks for years, the fuss over wet markets or the role of a single country in triggering the outbreak distracts from the larger reality of modern-day pandemics.

This is a crisis we have inflicted upon ourselves, they say. It’s both a bug and a feature of our modern, urbanized, and hyper-connected world. Billions are on the move in this global melting pot, creating rich new opportunities for business and cultural exchanges, but also introducing new health risks.

At the same time, our modern cities are getting larger and larger, gobbling up wild spaces, and putting us in greater contact with wildlife: from brown bears in the suburbs to packs of wild boars rummaging through trash bins for a snack. Throw in climate change, globalization, and a boom in global travel, and you get the conditions for a great comingling of species—people, animals…and contagions.

“Significantly” altered

In a report last year, the United Nations said three-quarters of the world’s land, and 66% of its marine environment, had been “significantly” altered by human actions. Native species in most of the major land habitats are in decline, while invasive species are on the rise. Meanwhile, urban areas have more than doubled since 1992, contributing to this loss in biodiversity.

As the United Nations Environment Program noted in an Earth Day blog post today, environmental protection means human protection. “Had we been further advanced in meeting the Sustainable Development Goals and the Paris Agreement on climate change, we could better face this challenge,” United Nations Secretary-General António Guterres said of the COVID-19 pandemic.

For tiny, invisible viruses, this truly is a boom time.

“There are more and more people on the planet, and with more demographic pressure we have to expand into new areas, places where, up until now, human beings hadn’t lived in a massive way,” said Jordi Serra-Cobo, an eco-epidemiology specialist at the University of Barcelona’s Biodiversity Research Institute and one of the world’s foremost experts on zoonotic diseases, or those that animals transmit to humans. “And when we destroy natural habitats, many species that have viruses that could infect us are in closer contact with the human race.”

Since COVID-19 exploded into a global crisis, an avalanche of questions have been lodged about what happened in Wuhan late last year that caused the outbreak to take root. Still more questions swirl around China’s ubiquitous wet markets and even the local taste for exotic animals such as the scaly anteater known as the pangolin, which at one point was a suspected vector of disease.

The COVID-19 virus probably circulated in animals for years—perhaps up to half a century—before it made the jump to humans in Wuhan, Serra-Cobo says. What we should be focusing on instead of wet markets, he adds, is how the COVID-19 epicenter resembles a lot of cities and towns everywhere on the planet.

“Why Wuhan? Because it’s a large business center, and there are a lot of students,” said Serra-Cobo. “If a virus passes to man in the middle of the Amazon, it has a much smaller effect because it is less connected.”

On the rise

Viruses like COVID-19, a beta coronavirus of the type normally carried by bats, pose a serious threat because they evolve very quickly, by mutating or by combining with others. 

Such animal-borne contagions are on the rise, says Joaquim Segalés Coma, director of the Barcelona-based Centre de Recerca en Sanitat Animal. Virologists estimate that about 70% of emerging diseases in humans are zoonotic—spread from animals to humans—and almost three-quarters of those come from wildlife. 

Including the 1918 Spanish flu outbreak, “most of the major pandemics have happened in the past 100 years,” said Segalés Coma, who is part of a consortium of scientists conducting basic research to help find a vaccine for zoonotic coronaviruses, a project he’s participated in since 2014. 

Researchers have zeroed in on the bat as the likely origin of the virus, but that reveals only a small part of the infection journey: They still need to uncover the intermediary between the bat and us. In the process, scientists have already considered, then ruled out, a long list of species—from the exotic (snakes and pangolins) to the kinds of animals you’d find at any butcher stand: (chickens and pigs).

“That intermediate has not yet been found,” Segalés Coma told Fortune.

Domino effect

What is clear is which species turned the spark into a fire.

“It’s very clear that COVID-19 originated in bats,” Serra-Cobo said. “Why did it now pass to humans? The fault does not lie with the bats. It’s that humans began to massively invade the habitats of bats.”

In the past 20 years, the world has seen the greatest explosion in human mobility in our history. That same period has also seen a boom in zoonotic epidemic outbreaks, including SARS, MERS, Zika, and Ebola.

“People are moving around more—they’re traveling by plane, by ship, by car,” Segalés Coma said. 

The number of airline passengers, for example, has more than doubled since 2000, to 4.23 billion in 2018, according to the World Bank. This global travel, matched by mass urbanization and the rapid deforestation it’s unleashed, has created ideal conditions for zoonotic diseases to make the jump from the wild to humans. 

“It’s become clear that the human being has modified the ecosystem in different ways, and that has increased the likelihood for potential spillover events,” said Segalés Coma.

Those spillover events will likely expand—with increasingly pernicious effects on human beings—unless mankind turns its focus on itself.

“We know very well what we have to do,” said Florian Liegeois, a virologist at the French National Research Institute for Sustainable Development. “The world looks surprised by the COVID outbreak, but scientists are not.”

Legislative fixes such as banning the global trade of bushmeat would be an obvious step toward mitigating the problem, he says, but so too are greater cultural changes necessary. Rethinking our relationship with nature—from the food we grow and consume to the waste we produce—would be the best measure for preventing another pandemic.

“We are trying to help [COVID-19] patients, which is important, and we are concentrating on finding a cure and a vaccine, which is also very important,” said Serra-Cobo. “But no one asks why this is happening.”

More coronavirus coverage from Fortune:

—The trillion-dollar question: How far will GDP fall?
—How Fortune 500 companies are utilizing their resources and expertise during the pandemic
—Thermal-imaging tech is on the rise. Can it help fight the coronavirus?
—Privacy concerns split Europe’s push to build COVID-19 contact-tracing apps
—5 veteran investors on how to approach the coronavirus stock market
—More surveillance and less privacy will be the new normal after the coronavirus has been contained
—Looking for a travel refund? Here’s what airlines, hotels, and theme parks are offering
—PODCAST: COVID-19 might have upended the concept of the best companies of the year
—VIDEO: 401(k) withdrawal penalties have been waived for anyone hurt by COVID-19

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