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Natural Barriers Are What Prevent Coastal Cities From Being Destroyed

New U.S. maps show how coastal habitats protect millions of people and real estate dollars from the threat of climate change.

Before industrial pollution began mucking up our waterways, New York City used to be surrounded by hundreds of millions of oysters clinging to peripheral reefs. The Florida Keys, meanwhile, had a wealth of coral—until it declined by 44% in the late ‘90s. East of New Orleans, canal dredging and construction destroyed tens of thousands of acres of swampy wetlands that served as buffers against flooding and severe weather. All of these once constituted "soft habitats" that protected our coastlines, but until now, it had been difficult to measure how much work they actually did—and continue to do in the face of climate change.

Researchers at Stanford University’s Natural Capital Project have indexed the entire American coastline, kilometer by kilometer, and measured risk of coastal flooding and destruction with and without these habitats. Combining several factors of coastal protection—including habitats, elevation, wave exposure, shoreline type, wind exposure, and sea level rise—into their measure of vulnerability in the year 2100, the researchers found that without habitats, some risks nearly doubled.

"I didn’t imagine it would be such a large difference," lead author Katie Arkema said. "[Coastal habitats] are like walls or shields, especially in places that are soft coastlines, like sandy beaches," she explains. "They will reduce wave energy and the height of waves that are moving to the shore. These ecosystems will also keep sediment in place—their root systems retain the sediment."

The more surprising findings came when researchers looked at the vulnerable populations who would likely be affected by these hazards. Researchers had been working on the model before Hurricane Sandy, but when it hit, the number of deaths affirmed the team’s findings on how people might be affected in the New York area. "We were essentially predicting with our models that in the future there would be loss of life in the Northeast. It did validate our findings, unfortunately," Arkema says. The researchers also found that a disproportionate number of poor Texans are protected by these barriers on the coast.

Current (left) and future (right) projections of socially vulnerable populations protected by coastal habitat.

Arkema and her colleagues didn’t stop there. They also mapped the property values protected by coastal habitats by square kilometer—on much of Florida’s coastline, for example, concentrated wealth in real estate is largely protected by these coastal habitats. Nationally, researchers estimate that these habitats protect $4 billion in home property values.

"Part of what was exciting about our paper is that in some ways it’s the first to start to bring science to that challenging question of how to we bring climate science into our coastal planning," Arkema says. Stanford’s risk maps could be incorporated into insurance companies’ analyses, for example, and could help figure out how to maximize money invested in resiliency.

The team is currently working with the Nature Conservancy to help inform investments stemming from the RESTORE Act in the Gulf. "We’ve talked with the Florida chapter to help make decisions on where restoration dollars should be spent," Arkema says.

Current (left) and future (right) projections of real estate protected by coastal habitat.

While the maps may be the first to measure nationwide coastal vulnerability by the kilometer, there’s still plenty of work to be done. How much should cities beef up their coastal habitats? And which habitats should they restore? "It’s going to be important to look at multiple strategies," Arkema says. "Coastal ecosystems need to be part of how we do this. But hopefully they’ll be part of a whole suite of creative approaches."