Many people left Europe’s cities in the pandemic. What will bring them back?

When the coronavirus exploded across Europe in March, it realigned city life, shifting office workers to their homes, shuttering the hospitality sector and reshuffling life for millions.

Unshackled from offices — many for the first time in their working lives — city dwellers throughout Europe began to leave, some to avoid the virus but others to escape cramped and pricey apartments and to connect more with the natural world.

Now, nearly a year after the first lockdowns and with months more restrictions looming, the easy assumption that most of the Covid-19 exiles would naturally return once the virus was tamed is being questioned. In the reverse of the old song, the question now is not how you keep them down on the farm, but how you dissuade them from moving there for good.

For city planners and urban design experts, that means beginning to grapple with problems that have long plagued many of these cities — housing affordability, safe transportation and access to green space — and have grown more urgent in the pandemic.

More broadly, cities will have to address desires about connecting with nature and “reconnecting with life,” said Philipp Rode, the executive director of L.S.E. Cities, a research center at the London School of Economics.

A similar urban exodus has occurred in the United States during the pandemic, with affluent New Yorkers retreating to second homes and Silicon Valley techies scattering across the country. In fact, it might be even more pronounced in the United States than in Europe.

“Broadly speaking, place loyalty in Europe is significantly higher than in the U.S.,” Dr. Rode said, pointing to past studies showing that even among cities in economic decline, those in Europe suffered relatively less population loss. “A lot of these places have very deep histories, very deep culture.”

Nevertheless, many European cities are introducing things like pedestrian and cycle-friendly commuting options and expanded green spaces. Milan, hit hard by the first wave of the virus, has designated more than 20 miles of cycling lanes as well as “parklets” in former parking lots.