The trouble with city planning is that it's about the future, while any city's crankiest constituents prefer the present or, in some cases, the past.

That irony seems especially potent just now, as 167 local governments across the Twin Cities region prepare documents aimed at telling the Metropolitan Council how they plan to grow between now and 2040.

The how-to-grow question is dividing metro communities perhaps as never before. Especially in Minneapolis, where officials drafted a provocative plan (on which public comments close Sunday) pushing the envelope on density citywide — but also in St. Paul and in inner suburban districts like Southdale in Edina and West End in St. Louis Park — the market is pushing urban-style infill development to a point never before seen in these parts.

Around every corner, it seems, our low-slung outpost on the northern prairie is looking more like a city. Surface parking lots that once dominated the commercial landscape are filling up with buildings, most of them residential, some of them taller than 20 stories. Along busy transit streets, new housing-over-retail buildings are popping up by the dozens.

The push for infill is modest here compared with what's going up in Denver, Seattle, San Diego and other faster-growing peer cities, but the causes and effects are similar. Market forces that once drove development almost exclusively outward are now also driving it upward — and in denser concentrations.

Since 2010, more than 60 percent of our metro population growth has come in the urban core or in the already-developed suburbs. Three of every five new homes built have been in multifamily settings. New households are consuming land at only one-third the rate of the previous decade. Those trends are major departures from past patterns. No longer are we growing almost solely at the edge and almost solely via the single-family home.

Not everyone is happy about this new, more balanced growth pattern. Political forces in the far suburbs, accustomed to reaping all the benefits of growth, blame not the market but the Met Council, some even calling for its abolition.

Meanwhile, some city and inner-suburban neighborhoods are mobilizing against the prospect of taller buildings, busier streets and more neighbors. Minneapolis' 2040 draft has drawn daggers for floating the idea of allowing fourplexes even in the leafiest, most established single-family neighborhoods.

"This threatens our most valuable and unique asset," one resident wrote on the city's official comment site. "There seems to be a conscious decision to destabilize residential neighborhoods," wrote another. "I will move out of my lifelong city if this goes through," another writer promised.

Among the most common objections: Fears about speculators, absentee landlords, neglectful renters, falling property values and a scarcity of parking spaces, as well as suspicions that city leaders are trying to employ zoning to solve our notorious racial disparities. "Social engineering is destroying the quality of life in this city," one writer concluded.

"This really isn't about density," said John Adams, veteran geographer at the University of Minnesota. "It's about a perceived threat to the social status that the middle-class home and its context represents."

Plans to further densify commercial nodes and transit corridors have drawn less resistance. Still, there's an obvious distaste in some quarters for the urbanized form. "Not everyone can ride bikes or take transit," commented one writer, injecting more than a little resentment toward younger, more enthusiastic urbanites. Indeed, there's a generational tone to many complaints.

Mayor James Hovland of Edina told of an older man approaching him after a meeting saying, "Everything was fine until you came along." The man then complained bitterly about "skyscrapers" rising in the Southdale district. Said Hovland, "Some people are offended even by the idea of a six-story building going up four blocks away."

Libby Starling, the Met Council's director of regional planning, described a tension between older and newer residents in places where infill is underway. "People make a big investment in their home and they develop a special attachment to their neighborhood," she said, "and they want that neighborhood to stay exactly the same as when they moved in, back when they were the newcomers."

Heather Worthington, Minneapolis' director of long-range planning, also sympathizes with the emotions involved. "We're picking a scab here," she said. "This is where people live. It's hard."

But she and others also detect a darker side to the discussion: anxieties tied to the populist, fear-driven politics now gripping much of the U.S. and western Europe — fears about newcomers, falling living standards, loss of cultural cohesion and a desire to turn back the clock and recapture the past.

In the end, however, city planning can't be about nostalgia. "This is about 2040. If we're not thinking about the next generations, what are we here for?" asked Worthington. "I like to ask people to think about their favorite 5-year-old."

Indeed, cities would be foolish not to anticipate and accommodate a future that lies so clearly before them. There is no mystery, after all, about the demographic, economic, environmental and cultural trends that are driving the market to offer denser choices in the coming years:

• An aging population with more than double the share of singles and empty-nesters by 2040.

• Smaller households due largely to aging and to falling birthrates among whites.

• A growing population of color with comparatively less inherited capital for home buying (our nonwhite metro population percentage will grow from 24 to 39 percent by 2040).

• Persistent income inequality and job insecurity due mainly to automation.

• An increasing need and preference for housing affordability, walkability and proximity to jobs, shopping and transit.

• A desire by governments to use land and infrastructure more efficiently while maximizing tax base, as well as a desire by some residents for healthier lifestyles on smaller ecological footprints.

Of all these driving forces, perhaps the most telling statistic is this: Near the height of the baby boom in 1960, half of metro households consisted of parents and children; by 2040, that share will fall to 20 percent. It should come as no surprise, then, that three-quarters of homes built between now and 2040 are expected to be attached or multifamily.

We live in an age of denial, however. Two wildcards could alter this outcome and derail an otherwise sensible development trend.

One is technology. No one knows how autonomous vehicles — whether cars, buses or trains — will influence development patterns by 2040. Predictions vary on whether new technologies will reward density, sprawl or both.

A second wildcard is politics. At the moment, extremists on the left and right seem bent on restoring the sprawl model. Liberals in Minneapolis, for example, have energized the antidensity crowd by overstepping on their fourplex idea. They should scale it back and redouble their emphasis on upzoning transit corridors and moribund industrial sites.

They've erred also by trying to inject social justice into the zoning code. With lower housing costs than the national average, the Twin Cities has less an affordable housing problem than a low-income problem. It would seem more productive to attack poverty through education, job training and social skills rather than to anger middle-class taxpayers.

Conservatives, meanwhile, are busy killing any attempts to supply the infrastructure needed to support a denser lifestyle choice. They see balance and variety as an enemy and, despite demographic trends, want desperately to bring back the autocentric sprawl model, as most clearly seen in their attempts to stop expansion of the Twin Cities' transit system. Indeed, the oil-based billionaires Charles G. and David H. Koch are pouring millions of dollars into stopping transit investments nationwide.

That's an unfortunate turn. With one driver for dozens, even hundreds of commuters, transit is already close to providing autonomous travel. Thriving cities in 2040 will be those that offer balance, choice and variety in housing and transportation. A diverse economy has been key to the Twin Cities' success for five decades. Likewise, a diverse cityscape, one that includes density, will make a better partner for a warming planet and a better competitor for jobs and prosperity.

Steve Berg is a Minneapolis writer and urban design consultant.