Scientists have a plan to help us to retreat and relocate in a changing climate

An ever-changing climate can put certain regions in the crosshairs of coastal flooding, heavy rain, erosion, and other risks.

Now scientists have charted landscapes to clarify when and how to implement “managed retreat,” the relocation or abandonment of development in the face of extreme weather risks.

“Many people have an apocalyptic vision of what managed retreat means—ripping people out of their homes and letting buildings fall into the sea,” says Miyuki Hino, a doctoral student in the Emmett Interdisciplinary Program in Environment and Resources at Stanford University and lead author of the study in Nature Climate Change.

“In fact, there can be a huge potential benefit for the economy and for communities leaving the past behind and going to a better place. Still, it won’t be the right solution for everyone.”

Hard lessons can be found around the world: sea level rise could displace nearly 190 million people by the end of the century, according to a 2011 study. Last year, the United States alone suffered 15 natural disasters that each caused $1 billion or more in damage, according to the National Oceanic and Atmospheric Administration.

Coastal communities threatened by sea level rise and heavy storms are particularly hard hit. In some areas, the cost to shore up eroding coastlines and rebuild storm-damaged homes is increasingly untenable.

“People will be on the move in a changing climate,” says coauthor Katharine Mach, a senior research scientist in the School of Earth, Energy & Environmental Sciences. “We can respond in a managed, strategic way or in a way that is just fleeing disaster.”

Relocating communities and abandoning at-risk structures might make sense on paper, but the social, cultural, and psychological obstacles can be insurmountable. The strategy is also less likely to find buy-in where structural protections such as sea walls and levees are in place.

On the other hand, relocation can preserve community networks and culture. For some, resettlement can also open the door to new economic opportunities.

For the new study, researchers analyzed 27 past and ongoing examples of attempts to implement managed retreat in 22 countries. From this, they created a conceptual model based on who benefits from retreat and who initiates it. The model lays a foundation for understanding factors likely to impede or promote adoption of managed retreat in various circumstances.

Researchers categorized the examples they looked at with one of four labels based on whether residents initiated the retreat and how much support they got from the party that would be implementing the move through buy-outs, infrastructure changes, or other financial support.

“We know change is coming, and there won’t be a one-size-fits-all solution for protecting and supporting communities at risk.”

The labels group similar cases, such as when the residents initiate the retreat and receive government buyouts of high-risk properties. Other groupings include cases where residents don’t initiate the retreat, but, because of the greater good to the region, the government buys or elevates homes and creates a floodplain to protect downstream communities. In a third grouping, the residents did initiate retreat but failed to gain support of the government to implement the move.

The findings show that relocation is most likely to occur when residents feel the environmental risks are intolerable, the retreat benefits broader society in some way, political will for retreat is high, and a societal cost-benefit ratio justifies the move—a scenario the group labeled “mutual agreement.”

By contrast, managed retreat rarely works when the benefits of retreat accrue to residents only or no one at all, or when political will is low and a societal cost-benefit ratio doesn’t justify relocation—a scenario the researchers label “hunkered down.”

While rare, instances of communities voluntarily acting before disaster strikes—and other new implementations of managed retreat—could shed light on how to get past various barriers to the approach, researchers suggest.

Among other avenues for exploration, the researchers suggest policymakers support community ownership of the relocation process, from selecting the resettlement location to designing its infrastructure. Before it comes to that, leaders would do well to create policies—such as permitting development until only the shoreline erodes to a certain point—that can support retreat if need be.

“We know change is coming, and there won’t be a one-size-fits-all solution for protecting and supporting communities at risk,” Hino says. “It makes sense to keep a range of options, including managed retreat, on the table.”