HAVANA (AP) — Havana starts on the Malecon, the elegant, crumbling coastal boulevard whose early 20th-century buildings face a sea that sprays them with salt and pounds them with massive waves brought in by cold fronts or hurricanes.

That sea is warming and rising. The hurricanes are getting wetter and more intense. Along with a lack of maintenance, climate change is pushing the Malecon toward collapse.

Seventy percent of the buildings along the oldest, most fabled stretch of the Malecon have deteriorated so badly that they require partial or total demolition, according to one recent study. And at least four other buildings are in the process of being demolished after floodwaters lingered on the island last month, highlighting the many signs of the trouble faced by Cuba and the wider Caribbean in an age of rising temperatures.

Cuban experts predict the Malecon may not be able to last in its current form beyond 2100, when waters along Havana's northern coast may rise as much as three feet, bringing larger waves and potentially catastrophic flooding.

"It's hard to think that the Malecon will survive as such," said architect Rolando Lloga, who has written a report on the boulevard and suggests eliminating many buildings and joining it with the next street over. "Nature is moving faster than the actions that are underway."

After Irma scraped the northern coast of Cuba from Sept. 8 to 10, killing 10 people, the Malecon was closed for three weeks due to cave-ins on the six-lane roadway, sidewalk and seawall, where tens of thousands of Cubans usually sit, drink, eat and enjoy breezes off the Florida Straits.

The 5-mile Malecon was built atop coral reefs and mangrove forests that once provided a buffer between the sea and inland areas. Because of its inherently exposed position, many of the buildings along the stretch have elevated entrances and other features meant to accommodate flooding.

But those early adaptive measures are already getting an update. Cuba is in the middle of a broad rethinking of its land-use and urban planning policies, which include limiting the size of buildings on the Malecon, rebuilding its seawall with a water-shedding curve, building wave-breaking structures along the coast, and changing the drainage and sewage system so that seawater doesn't enter and erode the Malecon from below.

Still, that may not be enough. While hundreds of historic and cultural landmarks around Latin America are threatened by climate change, neglect has left the Malecon in worse shape than most.

A January report by the Havana Historian's Office found that 52 of the 72 buildings along the oldest stretch, what's known as the traditional Malecon, are in poor condition and would require demolition.

Of the 726 apartments in buildings on the traditional Malecon, which is home to 2,555 people, only 46 were in good condition, according to the report. Ninety-eight were deemed "normal," 162 were "bad" and 420 were "terrible."

Thirty buildings were previously demolished between 1994 and 2013, according to the report.

For now, demolished buildings will be left as empty lots until the Cuban government finds the funds to build new, climate-adapted structures. Cuban regulations make new private construction virtually impossible, particularly in historic areas.

"The sea will always seek what belonged to it, and we have to find a balance in order to live together, in order to enjoy this public space," said Patricia Rodriguez, director of the office of the city historian's master plan.

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Associated Press writer Michael Weissenstein in Havana contributed.

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