Barrier islands are set to retreat at an alarming rate

As the bodyguards of the coast, barrier islands offer protection from storms and flooding, and if you have beachfront property, they protect your home. However, a paper published in Nature Geoscience predicts that barrier islands will begin disappearing 50 percent faster than they have in the past.

“These findings can be applied all over the world, but they may be particularly significant in the U.S., where houses are being built extremely close to the beach,” said study lead author Professor Giulio Mariotti of Louisiana State University.

Still, the barrier island situation is not so simple. Mariotti explained that there have been gaps in our understanding. “It is well known that barrier islands retreat as sea level rises, but it has not been clear how.”

Mariotti and co-author Christopher Hein of the Virginia Institute of Marine Science noticed that barrier island retreat hasn’t kept pace as sea levels have risen. 

To explore this question further, Mariotti developed a computer model. Many scientists thought barrier islands would retreat as fast as sea levels rose. However, Mariotti’s model shows a lag between sea-level rise and barrier island retreat. 

Mariotti explained why previous researchers got it wrong. “One reason previous models didn’t see the lag was because they assumed the geometry of the whole coastal tract – from the lower continental shelf to the upland boundary, including subaerial barriers, inlets and tidal channels ­- was frozen. However, the geometry can change and that’s what’s enabling this lag effect.”

The model makes a worrisome prediction. The model predicts that over the next 100 years, the rate of barrier island retreat will increase by at least 50 percent. The rate could climb further if storm strength and frequency continue to increase or sea levels begin to rise faster. The author also points out that this prediction can vary by region. 

Mariotti explained why his model is unique: “One of the most original parts of this model is it can run simulations over thousands of years but can also provide insights into decades, which is more interesting for management. At the same time, I can also run simulations over centuries and millennia, which allows the results to be compared with geologic data.” 

Although this model does not give us the best news, it provides some of the information we need to manage coastlines and a way to compare current conditions with Earth’s geological past.

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By Erin Moody , Earth.com Staff Writer