İstanbul has grown beyond what its transportation, water and disaster-response systems can support, and urban planners are urging Turkey to manage a planned reverse migration to relieve the strain, the Cumhuriyet daily reported, after the May 23-31 Eid al-Adha holiday break emptied the city and cut traffic congestion to as little as 5 percent of normal levels.
Urban planners and water policy experts told Cumhuriyet that the brief, holiday-induced calm exposed a deeper structural problem the city has failed to plan around: a registered and unregistered population that has far outpaced its infrastructure.
Although official figures put İstanbul’s registered population at 15.75 million in 2025, experts interviewed by the daily said the real number reaches 20 to 21 million when unregistered residents and temporary populations are included. They warned that even long-term planning scenarios, including 2053 master plan projections, do not expect the city’s population to fall below the 20 million range under current conditions.
İstanbul has long attracted migration from across Turkey because it is the country’s largest center of jobs, finance, industry, trade, education and services. The city accounted for 18.3 percent of Turkey’s registered population in 2025 and remained the province receiving the highest number of internal migrants, with 395,485 people moving to İstanbul from other provinces in 2024, according to data from the Turkish Statistical Institute (TurkStat).
The city’s economic dominance is another driver. İstanbul generates close to a third of Turkey’s gross domestic product, making it the country’s main magnet for employment and investment. That concentration has also produced high housing costs, heavy commuting burdens and pressure on public services.
The reason İstanbul empties during religious holidays is tied to the same migration history. Many residents maintain family ties in other provinces and travel to their hometowns during Eid al-Adha, while others leave for coastal or rural holiday destinations. The holiday itself ran from May 27 to 30, while Turkey’s extended public holiday break covered May 23-31. Cumhuriyet reported that the fall in traffic and public transport use during the break was visible enough for remaining residents to say they wished the city could always be that calm.
Pınar Pelin Giritlioğlu, a board member of the Chamber of City Planners of the Union of Chambers of Turkish Engineers and Architects (TMMOB), told Cumhuriyet that İstanbul’s 2009 provincial environmental plan had projected a population of 16 million for 2030, a threshold already exceeded.
Giritlioğlu said “unnatural” growth driven by mega projects outside planning targets had pushed the city beyond that framework and warned that projects such as Kanal İstanbul could add further pressure.
She said reverse migration had already begun among some students, white-collar workers, retirees and public employees, largely because İstanbul has become too expensive for many residents. Remote workers with the option to leave have also started moving out, she said.
“İstanbul has become very expensive for workers,” Giritlioğlu said, adding that the city, once attractive for public employees, has become a place many no longer want to be assigned.
She said the emerging tendency to leave İstanbul should be treated as a planning opportunity rather than an unmanaged crisis.
“The 20 million threshold is critical. İstanbul’s resources are no longer enough for its population,” Giritlioğlu said.
She also warned that any effort to reduce population pressure must be planned at the local, regional and national levels and should not turn into a process that displaces long-term residents in order to open space for wealthier newcomers.
“The first target should be to reduce the population gradually and in a planned way,” she said.
Water policy expert Dursun Yıldız, a member of the scientific board for the İstanbul Planning Agency’s environmental plan work, told Cumhuriyet that İstanbul’s water problem could no longer be treated as a narrow water-management issue.
A large share of the city’s water needs is met through inter-basin transfers, including systems that bring water from outside İstanbul’s own catchment areas. Yıldız said the European side of the city in particular faces pressure from rapid population growth, distorted urbanization and insufficient planning.
“The water problem in İstanbul is no longer only a water-management problem,” Yıldız said. “It has also become a spatial planning, population-density management and increasingly a reverse-migration management problem.”
He said land-use planning and water-resource planning must be handled together because transportation and construction projects can trigger new development, put pressure on water basins and weaken the natural structure of catchment areas.
As the city grows, Yıldız said, its water security becomes more dependent on supplies from other basins. He argued that the pressure could be reduced only by strengthening other Anatolian cities economically, distributing industry more evenly, supporting medium-sized cities and encouraging planned reverse migration.
Yıldız described reverse migration as a “national spatial balancing strategy,” particularly for İstanbul and Ankara, where population growth has put pressure on infrastructure and natural resources.
The debate also has a disaster-risk dimension. İstanbul sits near the North Anatolian Fault and is widely expected by scientists to face a major earthquake. Urban planners have long warned that high population density, congested transportation corridors and uneven access to safe housing could complicate evacuation, emergency response and recovery after a major quake.
Giritlioğlu said that in the event of the expected İstanbul earthquake, evacuating the population would be a major problem, making population pressure not only an urban comfort issue but also a disaster-management concern.
The experts stopped short of calling for rapid depopulation, arguing instead for planned economic and spatial policies: developing employment outside the city, strengthening medium-sized provinces, improving regional infrastructure and discouraging new projects that pull more people and capital into İstanbul.