Alexandria, Egypt’s fabled second-largest city and largest port, threatens to disappear beneath the waves within decades.

With the sinking of the land and the rising of the sea due to global warming, the metropolis founded by Alexander the Great on the Nile Delta is on the brink.

Even under the United Nations best-case scenario, a third of the city will be underwater or uninhabitable by 2050, with 1.5 million of the six million residents forced to flee their homes.

The ancient ruins and historical treasures are also in great danger from the Mediterranean Sea.

Already in 2015 and again in 2020, hundreds of Alexandrians had to give up homes weakened by floods.

Every year the city sinks by more than three millimeters, eroded by Nile dams that hold back the river mud that once solidified its soil, and offshore gas production.

Meanwhile the sea rises.

The Mediterranean Sea could rise by a meter (3.2 feet) within the next three decades, according to the direst forecast by the UN climate expert panel IPCC.

It would flood “a third of the highly productive agricultural land in the Nile Delta” as well as “cities of historical importance like Alexandria,” it said.

UN experts say the Mediterranean Sea will rise faster than almost anywhere else in the world.

“Climate change is a reality and no longer an empty threat,” said Ahmed Abdel Qader, head of Egypt’s Coastal Protection Agency.

Even under the best-case scenario outlined by other Egyptian and UN studies, the Mediterranean Sea will rise 50 centimeters by 2050.

As a result, 30 percent of Alexandria would be flooded, a quarter of the population would have to be relocated and 195,000 jobs would be lost.

Such a catastrophe would have dramatic effects on Egypt’s 104 million inhabitants, because “Alexandria is also home to the country’s largest port” and one of the most important economic centers, said Abdel Qader.

On the other side of the delta, the sea has already encroached more than two miles inland since the 1960s and engulfed Rosetta’s iconic 19th-century lighthouse in the 1980s.

All of this is happening as Alexandria’s population is exploding, adding nearly two million people in the last decade, while investment in infrastructure, like elsewhere in Egypt, has lagged behind.

The city’s governor, Mohamed al-Sharif, said the drainage system for the streets was built to hold one million cubic meters (35 million cubic feet) of rain. But with the more violent storms that have come with climate change, “today we can drop 18 million cubic meters in a single day.”

The changing climate is also playing havoc with Alexandria’s weather, which can go from unseasonably hot to snowy.

“We have never experienced heat like this at the end of October,” resident Mohamed Omar, 36, told AFP, with the temperature rising to 26 degrees Celsius (78.8 Fahrenheit), five degrees above normal.

The looming threat is also a hammer blow to the image of a city that happily celebrates its cosmopolitan heyday of the early 20th century with its art deco cafés and elegant avenues lined with Parisian-style apartment buildings.

Many Egyptians were horrified when then-British Prime Minister Boris Johnson warned at the COP26 climate change conference in Glasgow last year that Alexandria was in danger of disappearing “under the waves”.

“Yes, the threat exists and we are not denying it, but we are launching projects to mitigate it,” said Abdel Qader.

A huge belt of reeds will be planted along the 69-kilometer coast. “Sand sticks around them and together they form a natural barrier,” he said.

Warning mechanisms and wave measurement systems are also set to be set up soon, added Abdel Qader.

Alexandria’s rich and ancient heritage is particularly at risk. Most prominent is the 15th-century Mamluk citadel of Qaitbay, built on a promontory on which once stood the lighthouse of Alexandria, one of the Seven Wonders of the Ancient World.

Relentlessly lashed by the sea, a breakwater made of 5,000 giant concrete blocks was installed to protect it.

More were set up to limit damage to the 19th-century Corniche.

Destruction and rebuilding are nothing new for a city that once housed the Library of Alexandria, the world’s greatest temple of knowledge, until it was accidentally burned by Julius Caesar’s troops.

Neither its modern legacy, a gleaming building on the Corniche leaning towards the Mediterranean like a disk of the sun, nor the rest of the city can be left to a moat, Abdel Qader stressed.

“The West has a moral responsibility: it must help counteract the adverse effects of climate change that are the result of its civilization” and its industrialized model.

And Egypt will be hammering that message home when the UN COP27 climate talks begin there on November 6th.