Jennifer Bradley is a fellow with the Brookings Institution Metropolitan Policy Program. Her work focuses on land use and economic development in Great Lakes metropolitan areas.

People in Cleveland, Detroit, Flint and Youngstown, and in Bilbao, Leipzig and Turin, have plenty of ideas about what cities can do with vacant and abandoned land: urban agriculture; watershed restoration and stream daylighting; side-lot programs; extensive park networks; public arts zones; new museums.

What if the government used a fraction of the billions it spends to subsidize home-building on 'unbuilding' projects instead?

What we need is a new mindset. Physical growth has been a powerful American narrative, embodied in huge public expenditures from the Louisiana Purchase to the Interstate Highway System and the mortgage interest deduction. The nation now needs a parallel commitment to physical ungrowth. Ungrowth is not surrender but a phase of urban evolution.

Remaking a city is breathtakingly expensive, and the market won’t do it. Indeed, the lack of a robust land market is part of the problem in shrinking cities. It costs about $10,000 to demolish a single-family home in Detroit; about 12,000 vacant homes there need demolition. And clearing the land is just the beginning. Philanthropy has stepped up in Detroit and elsewhere, but the need exceeds most foundations’ resources.

Last year, the federal government allocated $836 million to clean up and reuse old General Motors sites. That should be the first of many federal investments.

The federal government spends $104 billion a year subsidizing home-building through the mortgage interest deduction. What if it took 10 percent, or even 1 percent, of that money to help places unbuild and reinvent? At the very least, cities should be able to reallocate money they already get from the federal government and use it for unbuilding.

When the federal government poured money into shaping cities through highway building, urban renewal and public housing, the results were expert-approved, fast and brutal. Ungrowth needs to be bottom up, slow and exquisitely careful. It will take a long time to convince residents of battered cities that the new city landscapes dreamed up by their neighbors, city planners, foundations, academics and outsiders are worth uprooting their lives for. Americans have been spending for growth for centuries. Our commitment to ungrowth, and new ideas about how cities change and what they look like, needs to be sustained for decades.