Photo of the intersection of Brickell Bay Drive and 12th Street in downtown Miami, which is flooded because of high tides
High-tide “sunny day” flooding now occurs 4 times more often in downtown Miami than it did just 15 years ago. All along U.S. coastlines, high-tide flooding occurs up to 900% more often today. Credit: B137, CC BY-SA 4.0

For a successful result, managed retreat should not be considered a last resort, and the process should start today.

The idea of moving from places endangered by rising seas, dangerous temperatures, or wildfires is a personal, communal, and national decision. The response at each level is based on which risks are tolerable and whose values are prioritized. But adaptation measures can provide a road map for how a person, a community, or even a country can proceed. Such road maps are laid out in papers recently published in a special issue of Science. The gist: For a successful result, managed retreat should not be considered a last resort, and the process should start today.

The Need for Adaptation Actions

Some degree of relocation is going to be necessary, said climate adaptation scientist Marjolijn Haasnoot of Deltares and Utrecht University in the Netherlands, lead author of one of the Science papers. Already, global average annual sea level rise has more than doubled its 20th-century rate to 3.6 millimeters. By 2100, sea-level rise may be 10-20 millimeters per year and seas could reach up to 1-2 meters above 2000 levels; seas will continue to rise beyond 2100.

So how much response will be necessary, and how do we do it?

Responding to rising seas—or other effects of the climate crisis, like wildfires and unlivable temperatures—requires adaptation. That response could look like resistance (e.g., building seawalls), accommodation (e.g., putting infrastructure on stilts), avoidance (limiting new development in hazardous locations), advance (building out into hazardous areas), or retreat, wrote Katharine Mach from the University of Miami and A. R. Siders from the University of Delaware in their Science paper. Retreat in the most basic sense means relocating homes and infrastructure in harm’s way. “Each adaptation action represents a distinct value-laden decision about what to preserve, purposefully change, or allow to change unguided,” Mach and Siders noted.

But strategic or managed retreat likely includes several different adaptation strategies, like relocating infrastructure and people, as well as restricting development and building protective barriers. Each adaptation action is probably going to be part of a community’s plan to deal with encroaching hazards, Mach said.

Water spills over from the Lafayette River in Norfolk, Va., onto Llewellyn Avenue just after high tide.
Water spills over from the Lafayette River in Norfolk, Va., after high tide even when there is no rain. Credit: Skyler Ballard/Chesapeake Bay Program, CC BY-NC 2.0

Haasnoot also added that managed retreat will look different in different places. That’s why she and her colleagues created a road map to help break managed retreat into bite-sized pieces—manageable, adaptable steps that align with goals like economic development, environmental conservation, and social justice. The Dynamic Adaptive Policy Pathways, or DAPP, approach is already being used by decisionmakers to address threats from rising seas in the Netherlands, United Kingdom, and New Zealand, Haasnoot said.

The authors break down retreat into three stages: a preparation or planning stage, an active retreat stage, and a cleanup stage. The planning stage alone can take decades, Haasnoot said. Within each stage are short-term, medium-term, and long-term plans and actions that should be adaptable as conditions change, she said. For example, she said, a community might start with declaring no-build zones for new development, then over time, relocate households in risky areas as opportunities arise and not allow new families to move in.

Community Engagement

Community engagement is of paramount importance.… Plans need to be “owned” by each community.

At every step along the way, Haasnoot said, community engagement is of paramount importance. Mach agreed, adding that any plans need to be “owned” by each community.

The government in Miami-Dade County in Florida, a region at exceptionally high risk from rising seas, has developed a coalition to address sea level rise adaptation strategies, Mach said. The current strategy is a 40-year plan to adapt to 60 centimeters of sea level rise. Miami-Dade’s long-term planning is “impressive,” Mach said, and involves years of community action.

But there’s a problem, said Julie Maldonado, associate director of the Livelihoods Knowledge Exchange Network, who was not involved in any of the recent Science studies. “There isn’t just one Miami, for example.” Understanding who and what constitutes a “community” is important, she said, as is “recognizing that ‘community’ does not equal geography, but also people’s deep ties and connection to place.” Although decisionmakers might consider a whole city or county—say, the city of Miami or Miami-Dade County—one community, the county and city are made up of many diverse communities with their own leaders and cultures. So there can’t be a “homogenized approach to relocation, as if one size fits all,” Maldonado said. Relocation plans cannot be a one-directional engineered resettlement. The process needs to be community driven, with community leaders front and center on the decisionmaking team, not just another stakeholder, she said. And that’s often not happening.

Some communities are being told they need to leave, to abandon their homes and their lands, “with their sovereign rights and self-determination being ignored, rather than guiding the decisions as rightsholders,” Maldonado said. And then where do they go? What happens in the full cycle of the resettlement? Where are the funding mechanisms to support the full process? she questioned.

Challenging Plans

Although learning from other places that have successfully implemented adaptation and even relocation plans while forging community collaborations is worthwhile, road maps must be considered with caution. They can fall into a “check-the-box approach,” Maldonado said, where outside entities might say, “We held a public meeting, so we did community engagement. Check.” But that’s not real, authentic engagement, she said, and any relocation plan that’s equitable needs to be a collaboration that includes, and is guided by, each affected community’s values and is community led.

A prolonged, strategic, managed retreat can be equitable, Mach said, as opposed to relocation after disasters, which usually isn’t. In the United States, most government buyouts of homes occur after disaster strikes. Even if the government gives a homeowner the value of the home predisaster, that is probably not sufficient for replacement, she said. Elsewhere, “people are forced to relocate out of informal settlements often without access to jobs or other basic needs.” These situations need to be avoided, Mach said.

Managed retreat is not easy, and some days it’s hard to be optimistic, Mach said. But “so many capable, brilliant, passionate people are working on this that it gives me hope,” she said. “And for adaptations, on a fundamental level, when things get bad, people dig deep and figure out solutions. That [also] gives me hope.”

—Megan Sever (@MeganSever4), Science Writer

24 July 2021: This article has been updated with changes throughout.


Sever, M. (2021), A road map for climate retreat, Eos, 102, Published on 23 July 2021.

Text © 2021. The authors. CC BY-NC-ND 3.0
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