Rising seas could swallow millions of US acres within decades

The water is coming.

There is no longer much doubt about this, as scientists increasingly document how global warming has accelerated sea level rise along coastlines around the world.

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But a new analysis released Thursday by the research nonprofit Climate Central reveals a troubling dimension of the economic toll that could unfold in the United States as hundreds of thousands of homes, offices and other privately owned properties slide below the high tide mark. next few decades.

Here are five takeaways from the research about the people and places that stand to lose the most, the potential ripple effects, and why the world needs to cut greenhouse gas emissions to finally stop rising waters.


1. Sea level rise will shift coastlines – and property lines

Researchers at Climate Central took scientific data on projected sea-level rise, as well as information on state tidal boundaries, and combined it with records on more than 50 million individual properties in hundreds of U.S. counties to identify parcels that are more at risk.

Their conclusion: Nearly 650,000 individual, privately owned parcels of land, on up to 4.4 million acres of land, are projected to fall below shifting tidal limits by 2050. Affected land could swell to 9.1 million acres by 2100 According to Thursday’s analysis, properties with a collective estimated value of $108 billion could be affected by the end of the century, based on current emissions. But, the authors noted, because full property values ​​were not available for all counties, the true total is likely to be much higher.

Changes could also come gradually at first, then quickly. In many communities, the authors wrote, structures are clustered in areas that are historically on safe ground. But once rising seas reach these densely developed elevations, “the number of buildings affected increases sharply.”

“As the sea rises, the tide lines rise in elevation, upslope and inland,” said Don Bain, a senior adviser at Climate Central and an expert on sea-level rise, who led the analysis. “People haven’t really internalized that yet — that, ‘Hey, they’re going to get me something by the sea.'”


2. The Gulf Coast and Atlantic Coast stand to lose the most

Not surprisingly, Louisiana, where the seas rise and the land sinks, faces a terrifying loss of property in the coming years.

Climate Central’s analysis estimated that more than 25,000 properties totaling nearly 2.5 million acres in the state could fall entirely below tide lines by 2050 — far more than anywhere else in the country. That would amount to 8.7 percent of Louisiana’s total land area, according to the report.

But other states also appear to be facing widespread threats. The top three at risk behind Louisiana are Florida, North Carolina and Texas, all of which have large areas of low-lying, threatened coastlines.

While properties in the Southeast may face the most collective risk, other states also have cause for concern. New Jersey and New York, for example, will also see thousands of properties fall below the threshold in the coming decades. The same for Maryland, where investigators could see more than 2,500 buildings affected.

The effects of sea level rise are already evident, with some communities facing the prospect of subsidence and a growing number facing nuisance or “sunny day” flooding.

Eventually, such issues “will go from something that’s rare to something that’s normal,” said William Sweet, an oceanographer with NOAA’s National Ocean Service and the nation’s top scientist on sea-level rise.


3. It’s not just flooded houses. It is about the erosion of tax bases.

The loss of homes and other property—especially those along the waterfront—isn’t just a tragedy for homeowners. It’s a surefire way to erode the revenue that municipal authorities need to operate.

“Ultimately, this is a local problem and a local story,” Bain said. “We fund local government through our property taxes.”

If sea levels continue to rise unabated, this poses more than just a problem for beaches and coastal flats. Ultimately it will translate into less taxable property and less money to fund schools and fire departments, fix roads, maintain sewers and provide other basic services.

“Decreased property values ​​and a smaller tax base can lead to lower tax revenues and reduced public services – a potential downward spiral of disinvestment and population decline, reduced tax base and public services, etc.,” Thursday’s analysis found .


4. The potential ripple effects are huge.

Erosion of tax bases is a big problem. But almost the only one. The study also found a litany of other complications likely to arise as sea levels rise ever higher.

“The legal and policy implications of these changes are complex and will likely vary between locations,” the analysis found. “These consequences extend far beyond the loss of tax revenue, as property owners object to paying taxes on submerged land.”

Beyond these initial shocks, municipalities and individuals will also be forced to deal with the significant costs of removing flooded structures and flooded septic tanks. Governments could be on the hook for abandoned properties, adding additional costs not covered by their budgets.

But even before then, communities are already struggling with the need to repair flood-damaged roads and streets, as well as overworked or outdated sewer and water systems. “How city and county management teams respond to these risks, or whether they respond at all, is important to the city and county’s future ability to repay debt and protect its creditworthiness,” they wrote. the authors.


5. The future is not (completely) set in stone.

The world’s leading scientists have found that given the carbon building up in the atmosphere after generations of burning fossil fuels, the rate of sea level rise is increasing and will continue for decades to come.

Those findings are consistent with a major report earlier this year from the National Oceanic and Atmospheric Administration, which found that sea levels could rise along the U.S. coast by about a foot between now and 2050—about as much change in next three decades. in the last century.

“That trajectory seems somewhat set,” said Sweet, who was not involved in Thursday’s study.

What remains undetermined is how communities across the United States are preparing for the changes they know are coming, and what this country and others are doing to slow global warming.

“If we get together, we can get to a lower curve, and that buys us time,” Bain said. “We do not want [seas] is growing so fast that it’s outpacing our ability to adapt.”

Sweet said data from NOAA and related efforts like Thursday’s study hopefully provide public officials and individuals with the information they need “so they can make the smart choices to best defend and prepare against the rise of the sea” – from supporting infrastructure to making thoughtful decisions about development.

But ultimately, he said, the world must act in concert to ensure the problem does not worsen indefinitely.

“Emissions matter, especially as we move beyond the next 20 or 30 years,” Sweet said. “You reduce emissions, you reduce the possibility of higher sea levels.”

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