Rising sea levels are threatening millions of acres of land and properties and billions of dollars in real estate tax revenue for coastal cities. After the devastation caused by Hurricane Ian last year and Ida the year prior, this news should come as little surprise. In 2022 alone, the U.S. has experienced 15 weather and climate disaster events each with losses exceeding $1 billion and 342 collective deaths, according to the National Oceanic and Atmospheric Administration.

A report from nonprofit group Climate Central found that flooding due to rising sea levels is shifting the tide lines that many coastal states use to delineate boundaries between public and private property. As the sea takes over low-lying public space and encroaches on private property, billions of dollars in properties are at risk. The destruction of this real estate, and the tax revenue it generates, will have severe implications for those states and localities and property owners within them.

Climate Central examined state-specific boundary definitions and weather data for more than 250 counties to discover the areas of risk. The researchers found that by 2050, more than 4.4 million acres accounting for 648,000 individual tax parcels will be at least partially below the tidal boundary levels. That means as many as 64,000 buildings and roughly 637,000 properties or, put in dollar terms, as much as $35 billion worth of value, might be wiped out within the next 30 years. Looking even longer term, more than $108 billion in assessed value—some 300,000 properties—is at risk from rising seas by 2100.

What’s behind this reasoning? In short, climate change: Global warming increases the earth’s temperature, along with that of seas and oceans. Water takes up more volume as it warms, so essentially these bodies of water are growing. Melting icecaps and glaciers also add to global water levels, further accelerating the rising rate of sea levels. When weather events like hurricanes occur, the likelihood of major flooding rises in tandem with sea levels.

So, while property and houses in coastal areas may have been built at tidal boundaries once deemed safe from flooding, rising sea levels are shifting that boundary. In recent decades, it’s been shifting closer to population centers. Areas that have already experienced flooding are going to see increasingly worsening floods, and the more inland the water reaches, the more destruction it will leave in its wake.

The Climate Change analysis took into account the state-specific tidal boundary definitions, allowing for a clearer assessment of the potential loss of taxable property. The boundary between private property and public waters is defined by individual state law; each state designates a land elevation based on different average tidal levels to set the boundary, so certain areas are at greater risk than others. Tidal boundary definitions vary by state and therefore the risk isn’t spread out evenly among affected cities.

Seas forecast to rise anywhere from 8 to 23 inches over the next three decades, with the northern Gulf Coast and mid-Atlantic being most affected. As more properties see increasing flooding risk, values will decline as insurance costs go up. Properties destroyed by flooding will see value completely wiped out. Reduced property values mean reduced property taxes that local governments rely on to fund schools, infrastructure, emergency services, etc. All these declines will ultimately impact the economic stability of communities.

In the current pace of global warming continues, more than 48,000 properties—mostly in Louisiana, Florida and Texas—could fall under high tide lines by 2050. It’s estimated that 9% of Louisiana’s total land area could be below water level by 2050.

Some locations within other states could feel even worse effects. More than 15% of the total acreage of New Jersey’s Hudson County, for instance, is predicted to be underwater by 2050, putting $2.4 billion-plus worth of land and buildings at risk—the highest value loss in the country. By value, it’s followed by Galveston, TX ($2.37 billion), Honolulu ($2.3 billion), Washington, DC ($1.4 billion) and Miami-Dade, FL ($1.3 billion).

While global warming is a massive, complex issue, Climate Central says there are steps that could be taken to address this problem of encroaching sea levels and the risks they present. For one, land use policies can be adjusted to encourage development outside, and limit new growth within, risk zones. Participation in the National Flood Insurance Program and the Community Rating System incentives helps to improve financial resilience for residents, indirectly supporting the tax base, and educating taxpayers may help them constructively participate in adapting the local economy and tax base to the rising sea.

Of course, ultimately reducing and eventually eliminating carbon pollution will prevent the problems identified in this report from getting much worse. The organization also encourages the utilization of science-based analysis to inform investments in infrastructure interventions, such as improving stormwater systems, raising roadways, building levees, or improving coastal wetlands, that will, at least for a time, help protect the tax base.


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