I went for a walk in the woods north of Istanbul last week — through a beautiful old forest that will probably be among the thousands of acres ruined if President Recep Tayyip Erdogan moves ahead with plans to build his craziest project yet: a 30-mile shipping canal parallel to the Bosporus.

Erdogan’s mega project would not just alter Istanbul’s geography. It would also destroy forested areas bordering the Black Sea, damage the city’s freshwater reservoirs and ecosystem, and significantly worsen the local impact of climate change.

Even worse, the plan involves the creation of a second city, expected to grow to 2 million people, along the banks of the new canal. Since it would be directly adjacent to Istanbul, this new urban area would make our already densely packed metropolis of nearly 16 million unlivable.

“We will build the canal, whether you like it or not,” Erdogan hollered the other day (in characteristically democratic spirit). He has been mulling over the idea since 2011, and clearly sees making a mark on Turkey’s topography as part of his historic legacy. “This project is treason,” says Istanbul’s new opposition mayor, Ekrem Imamoglu, who fervently opposes the plans. Roughly 60 percent of the public also opposes it, and at each of its stages citizens have been lining up to send petitions to protest. To no avail.

Erdogan says that the mega infrastructure project, estimated to cost anywhere from $13 billion to $25 billion, will attract foreign investment and boost Turkey’s economy during a downturn. Chinese investors are reportedly already lining up. Wealthy Gulf Arabs with connections to the government, including members of the Qatar royal family, have bought land along the proposed route.

All this is being planned by the leaders of a country with depleted foreign currency reserves, double-digit inflation and massive foreign debt. What Turkey needs isn’t more crony capitalism based on feverish construction, but a return to rules-based management. The costly project would empty Turkey’s coffers and further encourage Erdogan’s personalized control of the economy.

The government argues that the new waterway would help to moderate maritime traffic through the Bosporus by cutting back on the number of ships and oil tankers that pass through Istanbul. But it won’t. The 1936 Montreux Convention guarantees free passage of vessels through the Bosporus and the Dardanelles straits, connecting the Black Sea to the rest of the Mediterranean basin. Unlike the Suez or Panama canals, Erdogan’s project will not shorten the route used by ships. Since Turkey cannot block the straits, most vessels will continue to use the Bosporus, where they pay minimal transit fees.

Some of Erdogan’s allies have suggested that the mighty Turkish president could revoke Montreux if he wants to, channeling traffic toward the proposed new canal. This would be a dangerous move. The 1936 accord is one of the founding documents of the Turkish republic. For nearly a century, it has maintained a delicate balance by maintaining Turkish control over the straits but providing free access to civilian vessels from the Black Sea, including Russian ships. Tearing it up would put Turkey on a dangerous collision course with Moscow. (Russians did, after all, fight a dozen battles with the Ottomans over three centuries for access to the seas.) Russian President Vladimir Putin has already made it clear to Erdogan that getting rid of the treaty is a red line for Moscow.

When a group of retired naval officers recently penned an open letter warning about the dangers of scrapping Montreux, the government responded quickly. It accused them of fomenting a coup and swiftly detained 10 retired admirals. They have since been released, and Erdogan has declared that he has no plans to leave Montreux. Yet his antics have contributed to yet another sharp downturn in Russian-Turkish relations.

Erdogan is a master tactician who — much in the Ottoman tradition — is adept at playing the great powers off one another. He is dangling the Istanbul Canal as a way to attract Chinese money. He throws Montreux into the mix to remind his estranged NATO partners of Turkey’s importance in containing Russia. Meanwhile, he reaffirms his status as the only global politician capable of standing up to Putin one-on-one. This is where Erdogan wants Turkey to be — a stand-alone power negotiating with all sides.

As the Biden administration criticizes Erdogan for his human rights record and his overtures to Russia, the Turkish president will try to use the Montreux issue to polish his NATO credentials and mend fences with Washington. The news that Erdogan might pull out of the treaty raised eyebrows across Western capitals; the news that he had backed off was greeted with relief. This is one more crisis we don’t need. Washington announced that it would send two warships through the Bosporus to the Black Sea in support of Ukraine (though Turkey now says that the deployment has been canceled).

Yet whatever any outside powers have to say about the issue, it’s already clear that Erdogan’s project is set to become the next big battle in Turkish politics. The Istanbul Canal is an ambitious real estate development that can wreak damage on the environment and destroy Turkey’s ailing economy. The opposition is adamant about fighting it, and Erdogan seems adamant about building it.

Last summer, the opposition-led Istanbul city government put up a series of billboards that were later confiscated by the government. They posed the choice with laudable simplicity: “Istanbul or the Canal.”

I vote in favor of Istanbul.

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