Washington, DC, November 2, 2020 --  

Rising sea levels combined with defensive sea walls mean urban beachfronts will be gone by the end of the century.

When the Milne Ice Shelf in the Canadian Arctic collapsed into the sea in August, the last remnant of a once massive sheet extending off Ellesmere Island was finally gone.¹ This, combined with other ice shelf collapses in Antarctica and increased runoff from the Greenland ice sheet are bound to accelerate the rise in sea levels.

Satellite measurements show that sea level has risen by 9 centimeters since 1993, about double the longer-term rate increase from tidal gauge records dating to 1900.² Part of this increase is from thermal expansion of warmer water, and the other is from melting ice shelves and glaciers. Predicting future sea level rise is fraught with complexity and doomed to inaccuracy. Depending on whose prediction you believe, sea level will rise between 10 centimeters and 60 centimeters (about 2 feet) over the next 30 years.³

For worried beach lovers, last week brought good news. A University of Plymouth study found that sandy beaches will survive sea level rise provided they have a way of migrating inland.⁴ The researchers showed that sea level rise will accelerate natural processes that tend to move barrier islands inland, or erode sea cliffs inland over time. So long as the shoreline is allowed to move inward, waves and wind will just move sand inland and up in elevation as the sea level increases.

The big caveat, of course, is that this will only happen where people don't interfere with nature. Unfortunately, thousands of years of civilization has show humanity's stunning determination to do exactly that.

Puerto Vallarta's Lost Beachfront 1965-2012 Photos courtesy puertovallarta.net

Take Puerto Vallarta, for example. The broad sandy beaches of the oldest hotel areas that once welcomed Elizabeth Taylor and other jet-set gringos 60 years ago are gone. In their place are sea walls designed to block the natural forces of erosion that would otherwise threaten developments. Indeed, a long stretch of central Puerto Vallarta hardly has any sand at all. And this result comes from natural erosion processes that have nothing to do with sea level rise.

The same can be seen in older beach communities around the world -- in Galveston, Hastings, England, in Karala, India and Mũi Né, Vietnam. In all of these places, sea walls are replacing sand. History shows that anyplace where people develop property along a sandy beach, they will do everything in their power to stop erosion processes that threaten their property -- even if it means kissing the sand goodbye.

To be sure, many beach communities have learned to combat erosion by allowing the sand to move -- typically by building beach dunes to slow inland migration and by pumping sand from lagoons behind the barrier island or from the sea floor itself. But while dunes slow down erosion from wind and waves, and pumping sand temporarily reverses natural sand migration, neither technique does anything to combat long-term sea level rise. With sea level rise, you must let the beaches move inland.

Only wild beaches without adjacent human development can possibly survive. That's good news for Big Sur and the Outer Banks, but terrible news for the world's storied urban beaches -- think Miami, Rio de Janiero and Puerto Vallarta.

In these locations, many thousands of rich people with expensive property will vigorously resist encroachment by the sea. Future decades will see increasingly desperate efforts to fight extreme tides and storms. Property owners will build protective sea walls and import sand to retain small sections of beach that are most defensible. This will work for awhile -- perhaps for the one to two feet of rise predicted over the next 20-80 years. But further sea level rise will force an abandonment of sand. In its place will be reinforced walls and levies along the shore to protect land below the water level. Anybody who has walked up the stairs on the levy in New Orleans to view the concrete lined Mississippi River has seen a vision of this ugly future.

The loss of urban beaches will certainly hurt property values. But it will hurt them far less than the alternatives: letting the advancing waves pound buildings to rubble; or the condemnation and demolition of neighborhoods in the ocean's path. The inevitable decline in property values will come long before any of this happens -- buyers just need to see the writing on the wall. Nowhere is the threat to real estate more visible than in South Florida where a McKinsey Report estimated in January that property values in low-lying areas will decline by 5-15 percent in the next decade.⁵

Sadly, the urban beach paradise is doomed to extinction. So enjoy Rio, Miami and Atlantic City while you can. And take your grandkids if you have them -- by the time they get to be your age, urban beachfronts will be an artifact of history.

Notes:

1. CNN, Canadian Ice Shelf Larger Than Manhattan Collapses Into the Sea, August 8, 2020

2. NOAA, Climate Change: Sea Level, August 14, 2020

3. Ibid.

4. The Science Times, Will Beaches Survive Rising Sea Levels?, October 28, 2020

5. Miami Herald, As seas rise, your coastal home in Florida could lose value. One report says 15% by 2030, January 16, 2020