In Turkey, they dreamed of something like this since the 16th century. The Bosphorus is difficult for shipping and is currently overloaded. A lot of oil tankers are moving along it, which affects the environmental situation. Traffic is growing every year, and the number of incidents is growing. The new canal is supposed to be built west of the Bosphorus. The European district of Istanbul will be divided into two parts, and the city center will turn into an island.
Environmentalists put forward several claims to the project. First, a bulldozer will have to dig only part of the canal: its route goes through the Sazlidere reservoir. This reservoir is a large source of fresh water, and during the construction of the strait it will become saline. We will have to solve the issue of water supply in Istanbul: to drill many wells. But even now, during periods of drought, water outages occur.
Environmentalists are alarmed by the mutual influence of the waters of the Black and Marmara Seas. It is believed that as a result of the construction of the Istanbul canal, the Black Sea will become saline, and the Marmara Sea will be desalinated. This can lead to the fact that part of the inhabitants of both seas will not be able to adapt to new conditions and will die out.
Another concern is related to the possible penetration of hydrogen sulfide from the Black Sea into the Marmara. However, oceanologists believe that this will not happen: hydrogen sulfide in the Black Sea exists only at great depths, and the problem of salinization and desalination will affect only local areas, and even then only slightly.
The idea is of interest to political scientists. A new strait will be paid. It is not clear how Turkey will motivate ships to go along it, bypassing the free Bosphorus. Another point: shipping through the Bosphorus is regulated by the Montreux Convention, which imposes restrictions on the passage of military vessels of non-Black Sea countries. In this strait, only the Turkish authorities will dictate the rules.