The recent report from the World Health Organization on the origins of the coronavirus pandemic is largely inconclusive. The truth is, we may never get clear answers to what brought us covid-19. Nevertheless, there’s a lot to learn from the report, and though the authors prudently avoid definite conclusions, there is one thing we now know for sure: The speed and scale of Chinese urbanization played an important role in the pandemic. And the country’s continuing push for rapid urbanization makes another pandemic more likely.

The WHO report identifies three possible pathways for the origin of the pandemic, all of which can be traced back to bats or an alternative, as-yet-unidentified “Animal X.” In order of probability, these pathways were: transmission to humans via an intermediate animal host (such as livestock); transmission directly to humans; or transmission via contamination of the food supply chain (also known as the “cold chain”).

What the report doesn’t say is that each of these mechanisms is intimately linked to China’s rapid urbanization and the resulting transformation of the nation’s food systems. This relationship is not limited to China. As urbanization expands worldwide and the space for wildlife shrinks, human environment interactions intensify and zoonotic transmission of viruses from animals to humans becomes easier. But the speed and scale of China’s urbanization drive deserve special scrutiny.

China’s state-led push isn’t just about building megacities like Wuhan, a sprawling metropolis of more than 11 million people and the epicenter of the early pandemic. More importantly, it is about transforming the nation’s vast countryside. Since the early 2000s, China’s leaders have taken a deliberate approach to rural development, including a raft of policies that have sought to integrate rural areas more tightly into urbanization. These initiatives include plans to permanently resettle hundreds of millions of rural people in towns and cities, where they will help drive growth in consumer demand, including for meat and other specialized foods. Meanwhile, the villages they leave behind are being transformed from communities of subsistence-farming households into industrialized farms integrated into regional, national and international food networks. These and other transformations promise real improvements for a large portion of China’s population, but this policy of rural urbanization also entails hidden costs, one of which is the increasing risk of zoonotic epidemics.

Take, for instance, the pathway the WHO report deemed the most likely origin of the pandemic: transmission via an intermediate animal host. In this scenario, the novel coronavirus first circulated in bats, then spread to another animal species, then from that animal to humans. As the report makes clear, the likelihood of animal-to-animal transmissions increases in the context of high-density, industrialized farming of livestock and wildlife, which has become more prevalent in China in response to the rising meat consumption of the nation’s growing urban population. China’s industrialized pork and chicken production is an important source of emergent avian and swine flus, and one of the underreported stories of 2020 was the identification of a new strain of swine flu in China that has pandemic potential.

Urbanization also plays a role in the second pathway identified by the WHO: direct transmission from a bat to a human. This is partly because the rising affluence associated with urbanization leads to greater demand for wildlife, the consumption of which can sometimes serve as a status symbol in Chinese culture. (Exotic species are also used in traditional Chinese medicine.) While China’s government banned the wildlife trade in the wake of the pandemic, much of this sector operates illicitly, and some rural people have become dependent on the sale of exotic species for their livelihoods. This is especially true as China’s urbanization drive erodes the sustainability of subsistence economies. The consumption of wildlife, such as bats, might once have formed an occasional and highly localized supplement to subsistence livelihoods. But as China’s food system has become increasingly specialized, these animals have been transformed into niche products that can easily travel to the other side of the country.

This leads to the third potential pathway identified in the WHO report: contamination in the “cold chain.” This mechanism, which the WHO has labeled “possible” but not likely, has been advocated by China’s government as the likely cause, perhaps to deflect attention to other parts of the world. According to this theory, the coronavirus could have originated elsewhere and then been imported via contaminated frozen food to Wuhan, where it seeded the pandemic. But the rapid expansion of Chinese urbanization plays a role even here. The construction of China’s frozen-food infrastructure is a relatively recent intervention meant to enable the industrialization and urbanization of the food system. This infrastructure has integrated markets that were once primarily local into sprawling regional, national and international networks that allow the rapid transmission of pathogens from one part of the world to another. Many of the urban changes in China’s food systems are also now being replicated in and connected to other parts of the world through the Belt and Road Initiative, including, prominently, Southeast Asia, which the WHO report repeatedly mentions as a potential alternative origin point for the coronavirus.

The dangers produced by the industrialization, specialization and integration of agriculture are not unique to China. The world’s increasing urbanization and the resulting transformation of its food systems mean that pandemics could arise anywhere, anytime. But the speed and scale of these changes in China make it particularly vulnerable at the moment — especially as the government’s regulatory and monitoring systems struggle to catch up. The WHO report documents multiple investigatory dead ends where data was not available or supply chains could not be traced.

The lack of a definitive conclusion thus reminds us of one of the fundamental features of an increasingly urbanized world: complexity. Socio-ecological relationships that were once limited to a single village now span the globe. And where a local outbreak could easily be traced to a single source, the origins of the global pandemic potentially entangle thousands of individuals and are now frustratingly opaque. In urbanizing our cities, we have also urbanized our agriculture, our environments and, ultimately, our pathogens.