[The American Conservative’s New Urbs project asked experts to respond to Benjamin Schwarz’s May/June 2016 cover story critiquing adult urban playgrounds. This is the first of two comments on “Cities Without Children.”]

Our cities are entering a defining moment. The young professionals lured into dense, walkable neighborhoods have resurrected our urban cores and many of their adjoining neighborhoods. But with this success has come the perception that cities are back, and that we have undone decades of damage from poor planning policies and urban sprawl.

The reality is that city streets may be teeming with activity, but they are deficient in diversity and sustainability. Planners or elected officials have failed to create urban communities that are made for everyone, which as Benjamin Schwarz detailed, betrays a central principle of the very Jane Jacobs we often cite as our precedent and inspiration.

The resurgence of cities was founded on the pursuit of hipness. Now there was an alternative to the suburbs, which had begun to show their wear and tear and were no longer enchanting to an emerging generation, one that valued place over material objects. Later this growth continued on a more complex set of principles, that urban revitalization benefits the health, economics, and environment of both the city and its inhabitants. Living in the city became less about being cool, and more about taking better care of the environment, our wallets, and our well being. And we, planners and city officials, have elected to exclude a very large segment of the population from these benefits.

We focused on a single demographic, enamored by their ability to fill a coffee shop or a public plaza, while giving little thought as to how they could remain in our cities as they age, change, or grow. Nearly every city in the country, large and small, entered into the bidding war for young professionals, seeking short-term wins while they failed to consider the long-term investment that these citizens actually represented.

We are not likely to lure very many families from their suburban homes into our urban centers. That would require a substantial lifestyle change that many would not be comfortable making. But resident retention should be a vital strategy for all cities, particularly as the millennials age and their household compositions evolve. Recent birth trends have shown that the oldest of millennials have begun to have children, and the younger members of the largest cohort in American history will follow suit. With costs rising, and housing options limited, it is reasonable to believe that many of these households, those who helped resurrect our cities, may very well leave just as they are hitting their peak earning years and seeking neighborhood stability.

The needs of these young households are complex, but it is clear that their presence strengthens communities. Everyone benefits from good schools, which attract top talent, improve property values, and provide a valuable community resource. Diverse housing options, those including more than studio and one-bedroom apartments, can create a natural lifecycle in a neighborhood that allows residents to remain and invest in their community. Quality parks provide more than just paved plazas or green space to walk dogs, they create recreation opportunities for everyone. And ultimately, all of these resources are more efficiently distributed and provided in a denser, walkable environment. We may find that if cities take down the “18+ only” sign that exists in our urban neighborhoods, we can reclaim the type of neighborhood vitality, investment, and character that Jane Jacobs describes and that so many people still long for.

Given the complex needs of families, and the lure of inexpensive suburban housing, it will take good public policy to establish the true urban vibrancy that cities, urbanists, and planners pursue. This does not mean an axe-wielding set of policies that drive every family household to the city. That is how we established the suburbs and all but eliminated the option of families living in cities.

Rather, we need a carefully constructed set of incentives that creates opportunities and options. Incentives should encourage diverse housing options and functional design that satisfies the “missing middle” emerging in every city across the country. Means should be sought to encourage collaboration between cities and school districts to properly manage siting and shared resources. Cities must market themselves and educate families that urban neighborhoods are an economically efficient, safe, healthy, and viable living alternative—the inverse of traditional thinking.

The fastest growing birth rate is occurring amongst the oldest millennials, and ultimately most will choose to have children. Maybe later in life, and maybe fewer, but the largest generation in America will produce a significant number of children, and providing them with living options that benefit the health of cities and families should be a priority. As a result, planners and city officials may just end up with the level of urban vitality that they have been pursuing so strongly. Otherwise cities will see a surplus of empty one-bedroom apartments and a commercial market that becomes less and less relevant.

Creating living options in urban, walkable neighborhoods for families, particularly those in the middle class, is not about satisfying a unique market niche or a particular political agenda. Several surveys have indicated that families would be willing to make sacrifices in order to remain in urban neighborhoods or believe that having a family should not require leaving the city.

We should create opportunities for families and children to enjoy the benefits of cities in the same way that we market them to young professionals. Our existing policies have eliminated this option.

Bradley Calvert is a city planner in the Seattle metropolitan region and is a parent living in Downtown Seattle. “New Urbs” is supported by a grant from the Richard H. Driehaus Foundation.