Trained as an archaeologist, Nicolas Gauthier couldn’t help but be drawn to the idea of civilizational collapse—the legendary fall of complex societies like the Romans, the Maya, and the Egyptians. Even now, he finds it fascinating to consider how different forces could converge to undermine a civilization.
“It is like a perfect storm or, to borrow a word from historians, a fatal synergy,” said Gauthier, assistant curator of artificial intelligence at the Florida Museum of Natural History at the University of Florida. “Basically, when one thing starts to go bad, other things go bad too, and you have this feedback loop that strikes societies.”
Today, Gauthier feels like he has witnessed similar synergies unfold in real-time. Large-scale inequality, political conflict, social upheaval, climate change, and environmental degradation all provided a context for the COVID-19 pandemic, the consequences of which researchers are still struggling to comprehend.
“The challenge is trying to understand how all these factors are interrelated in a global pandemic while we’re still in it,” said Gauthier. To truly grasp what is happening in the present, he believes researchers must look to past pandemics that have already run their course. Specifically, he has set his sights on the Black Death, a devastating pandemic of bubonic plague that spread for centuries, killing millions.
With a Climate Change and Human Health seed grant from the Burroughs Wellcome Fund, Gauthier and his collaborators have used the Black Death as a case study to explore the long-term links between climate change, human behavior, and infectious disease. As climate change rapidly accelerates, uncovering these linkages could prove critical to pinpointing future disease spillovers, predicting the next pandemic, and preventing the worst possible outcome.
Benefit of hindsight
The Black Death was a rapid and devastating demographic disaster, the most significant in documented history. During one five-year stretch it swept away 40 to 60 percent of Europe’s population. The deadly disease was the result of plague, caused by a bacterium called Yersinia pestis, which was transmitted by fleas that lived on rodents.
Some research suggests that climate change may have played a role in the emergence and spread of the plague. For example, climate oscillations can cause rodent populations to boom and bust, sending a surplus of infected fleas through the ecosystem. Similarly, climate-induced food shortages can lead to stress and malnutrition in the human population, increasing the number of hosts susceptible to the disease.
“Untangling historical climate-pathogen spillover linkages will help us come to terms with past disease outbreaks but also assess the risk of similar spillover events today,” said Timothy Newfield, a historical epidemiologist and environmental historian at Georgetown University. “There will never be another Black Death, as we no longer live in the 14th century, but plague reservoirs still exist in over 25 countries on four continents.”
Newfield has helped Gauthier gather historical records of climate variability and disease outbreaks during the five-year Black Death and the five-century plague pandemic that followed. Those documents, along with data from tree rings and pollen cores, have enabled the team to start piecing together what life was like back then. In some regions, such as the big cities of Western Europe, there is plenty of data to work with. In others, such as Africa, the Middle East, and Asia, the records of the plague are few and far between.
“What we’re trying to do is fill in the gaps,” said Gauthier. “We’re building computer simulations and models in places where we have really good data, and then trying to use them to make predictions in places where we know very little.”
Seed funding from the BWF has given the team access to high-performance computing technology, which they have used not only to power their research but also to train future researchers. Last summer, they piloted an undergraduate research experience in climate and disease modeling centered on the Black Death.
“You usually don’t see undergrads doing research at this level. But we have one of the largest universities in the country, so why not use those resources in terms of students,” said Gaby Hamerlinck, a quantitative ecologist and educator at the University of Florida. “That’s one of the reasons I was so excited to work on this project, because it’s a great opportunity to engage with undergraduate students.”
Together, Hamerlinck and Gauthier have supervised five early-stage researchers as they delved into the details of 14th century history and modern-day coding, along with the intricacies of host-parasite interactions. “We have very weird discussions with our students about things like how many fleas are on the average rat,” said Gauthier.
The students, having lived through a pandemic themselves, proved eager to learn more about the factors that might drive the next outbreak.
“Everyone now has a visceral understanding of how these pandemics work,” he said. “They’re able to connect this otherwise very abstract historical event to their personal experience, which is highly motivating, and channel that into a better quantitative understanding of infectious disease.”
The researchers said it has been easier than they thought to find connections between climate and disease, even using models generated by a handful of undergrads with software so simple it was originally designed for kindergarteners. For example, their initial models showed that regions with large-scale droughts or cold snaps often went on to experience big outbreaks of the plague.
“That’s the beauty of this approach—you don’t need to build complex computer models to answer some really interesting questions,” said Hamerlinck.
Beyond the plague
With such promising preliminary data, the team feels motivated to expand the project further. Hamerlinck and Gauthier are designing a study to assess whether their undergraduate research experience on the Black Death increases students’ general confidence in computational modeling as well as their desire to pursue a career in the discipline. A new postdoctoral fellow is joining Gauthier’s lab in January and will build upon the work of the undergrads, adding layers of complexity to their computational models. And the team is beginning to make plans for future field work, informed by their models, at historical plague sites in Europe.
“This line of questioning does not have to be limited to the plague,” said Hamerlinck. “Once our simulation is completely built and tested, it could be adapted to other diseases and time periods, helping us take advantage of thousands of years of insights into climate change and infectious disease.”
Ultimately, the team thinks those insights could give researchers and policy makers a way forward in addressing the health impacts of climate change.
“I am generally optimistic,” said Gauthier. “Part of it is seeing how much we as human beings can rebound from disaster. Things might have to get very bad to motivate the kind of responses needed for our survival, but I think that will happen in the end. It’s a race against time.”