Emotions and levels of threat affect communities’ resilience during extreme events

Ramirez-Marquez, associate professor and division director of Enterprise Science and Engineering at Stevens, who grew up in the earthquake-prone Mexico City knows this first-hand. “Whenever there's an earthquake, a city-wide alarm goes off and everybody leaves wherever they are and stays in the middle of the street — that's a prevention phase,” he says. “Then there's a restoration phase when people engage with others in the community, whether it's sharing food and water or helping rescue people from under the debris.” The community's solidarity and togetherness — one for all and all for one, per a Latin proverb — are key to bouncing back.

In scientific terms, this togetherness is defined as community cohesion, which encapsulates the sense of belonging, mutual support among members and shared values or sentiments, all of which boost community's ability to withstand disasters. But whether this cohesion directly influences how well a community recovers from extreme events is not known, explains Alexander Gilgur who had studied this subject with Ramirez-Marquez as a Ph.D. student. “Resilience is a measure of how quickly and/or effortlessly the system recovers from a disturbance,” says Gilgur. “The causal relationship between cohesion and resilience appears logical, but it has not been proven mathematically.”

To address that issue, Gilgur and Ramirez-Marquez developed mathematical techniques to measure community cohesion and its resilience, which they outlined in a recent paper, published in the journal of Socio-Economic Planning Sciences. They investigated two case studies of the same San Francisco Bay Area community during 2020 wildfires and during 2022-23 rainstorms.

In their work, they found that during the less intense adverse events such the rainstorms, the community performance improved despite the increasing stress levels. However, in high-stress disturbances such as the wildfires, the community's performance suffered. “We found that there's a negative correlation between the resilience of a community and the strength of disturbance,” says Ramirez-Marquez.

In fact, in some cases, the disturbance could be so strong that people may forsake their community. Ramirez-Marquez cites the recent Los Angeles fires example (which wasn't part of the study, but is telling), where more affluent residents hired private firefighters to keep their houses safe. “So when the stress is very strong, some might say, ‘oh, well, I don't care about the community, I care about myself.' The stress can be so high that the concept of community cohesion no longer stands.”

The scientists also found that the emotion intensity has a strong effect on community cohesion. “For helping communities be more resilient, emotional engagement is a very important factor,” says Gulgur, adding that it doesn't matter whether emotions are positive or negative. “Anger and fear are equally powerful as joy and love.” On the contrary, people's economic level does not have a direct effect on the community cohesion, “because the disaster might affect everyone,” says Ramirez-Marquez.

He notes that developing metrics to assess community cohesiveness and resilience offers practical benefits. If we can establish the causal link between cohesiveness and resilience, we can then set thresholds, limits or targets — and use these metrics to implement policies that aim to reach the desired numbers to improve resilience.

“Community cohesiveness is essentially a social glue that holds people together,” Ramirez-Marquez says. Quantifying that glue is challenging, yet being able to do so can help indicate whether a given community is resilient or can be stronger. “These metrics can then be used by policymakers to implement policies that make communities more resilient.”