By their nature, cities are dynamic and ever-changing, shaking off the past and constantly reinventing themselves to face the future. But something seemed to happen to U.S. cities over the last decade, a kind of stasis in the face of rapid change. That may seem counter-intuitive, considering just how much urban America changed, from the introduction of new technologies and startups to building booms, increased gentrification, and rising rents. But time and time again, cities were more reactive than active.

Perhaps it wasn’t as much stasis as it was putting off tough decisions. Arguably, U.S. cities found themselves in a reactive stance throughout the 2010s: trying to bounce back from the recession and housing market crash, trying to decipher and regulate new technologies, working to create affordability and equity, and figuring out how to move away from business as usual in the face of the climate crisis.

For the most part, cities and their leaders muddled through all of these changes. Has there been an occasional flash of brilliance, brave stance, or progressive policy? Of course. But have cities truly made tough, bold, brave choices to embrace the future? Look at the New York City subway, arguably the symbol of urban America. Its problems have been evident for years, and yet no leaders have shown the guts to fix it. Or take the homelessness crisis in Los Angeles, San Francisco, and so many of our other big cities. How many politicians stepped up to build more supportive and affordable housing at the scale the crisis demands?

The 2020s will be just as, if not more, uncertain than the previous 10 years, with many of the same issues at the forefront. But the time for putting off hard choices may be at an end. Municipal governance will require bold action to take on the challenges we face, especially the reckoning with climate change and an ever-warmer planet. Here are the key issues that city leaders will be forced to confront over the next decade.

Car-free or car-focused

This will be the central question mayors, planners, and citizens ask about how they govern and where they live. Will we double down on cars and car-centric development during a decade of increasingly bad climate crises, traffic congestion, and air pollution, or will we reposition city transportation and development to prioritize pedestrian access and safety? The arrival of autonomous vehicles and the increasing availability of electric vehicles seem to point to a middle route, a future of safer cars and less pollution that doesn’t require a wholesale shift in how our cities look.

But that attitude—that we can wait, that the current system requires a modification, not an overhaul—both puts off tough decisions and ignores the rapid and successful rise of car-free urban policy. The last few years have seen a portfolio of initiatives already take shape in major cities across the globe, including emissions-free zones, congestion pricing, bus rapid transit, and bike sharing. It’s been proven that walkable urban areas are more valuable, in terms of both real estate and commercial activity. We know air pollution is a critical crisis, and that transportation emissions have become the largest source of carbon emissions in our cities. The predicted rapid rise in e-bike sales suggests a hunger among many for a car-free transit alternative. City leaders, and national leaders, will need to overhaul our transit funding system, stop widening highways, and think about more sustainable planning and zoning to make such a big leap. But increasingly, doing nothing seems like a dead end.

The rise of the self-powered city

Earlier this year, a report by the C40 coalition of cities working to limit carbon emissions and climate change, titled “The Future of Urban Consumption in a 1.5ºC World,” found that 85 percent of the emissions related to goods and services in these cities are generated outside city limits. Cities have enormous economic reach and a significant environmental footprint, made much worse by the significant amount of carbon burned elsewhere to provide power. That’s why this decade will see increasing shifts towards energy efficiency⁠—see New York’s green building code, or Berkeley’s decision to ban natural gas in new buildings⁠—especially for cities serious about cutting their emissions (numerous U.S. cities have signed pledges to switch to all-renewable power).

Tyson Woeste, venture partner with Fifth Wall, a firm that invests in real estate technology, says efficiency will be big business. “The real estate industry consumes 40 percent of all energy globally, emits 30 percent of total carbon dioxide, and uses 40 percent of all raw materials,” he says. “Construction and demolition account for 25 to 35 percent of all waste generated in certain markets. So if we want to make progress in the looming climate crisis, our first order of business needs to be radical change across the real estate business.”

But, in what may be one of the greenest steps cities can take, many will push policies and developments that will not just decrease power usage within city limits, but increase local power generation. We’re at a point where need and technology meet: Solar power is getting cheaper, urban solar installations are getting more common (especially community solar projects that allow renters to tap into renewable energy), and pilot programs are underway to create urban energy microgrids.

That last point may be one of the most salient; in the face of climate change and the kind of power shutoffs seen in places like Northern California, cities will want more control over electricity generation and distribution. Audrey Lee, a vice president at Sunrun, a company that installs renewable power systems, says that with increasing wildfire risk in California, she has already seen more and more customers looking to set up solar panel and battery systems. She predicts that rooftop solar with a battery backup will be cheaper than electricity in a few years (especially compared to paying to fuel a diesel generator when the grid fails). Will cities see this technology as an opportunity to cut emissions and become more sustainable?

Can we live together?

One of the biggest challenge for cities going forward will be density, and the pursuit of cities that provide more housing for everyone. Upzoning, or changing building regulations to allow for taller, denser construction as well as more units in a single lot, will remain one of the most contentious issues facing city leaders, as residents in single-family neighborhoods continue to push back against efforts to densify and diversify.

It’s an especially important debate because so many other issues are directly intertwined with the pursuit of more housing within city limits: equity and economic mobility, cutting carbon emissions, and building a 21st-century transportation system. Minneapolis’s radical 2040 plan, which upzoned the entire city, Oregon’s statewide ban on single-family zoning, and California’s continued struggle to pass related legislation around transit-oriented development are merely the first chapters in what will likely be a city-by-city battle to change how and where we build homes in the future. This is why YIMBYism (or yes in my backyard, a political movement supporting more and denser housing construction) may be an enduring part of progressive urban politics for years to come.

Deciding what to save, and what to leave behind

The 2010s were the decade when high-profile hurricanes, California wildfires, and Midwest flooding made undeniably clear that climate change was happening in the present. As that process accelerates in the 2020s, it will mean changing patterns of rainfall, more flooding (especially in the Midwest), more storms, and ultimately less land. For many cities, especially low-lying coastal cities such as New York and New Orleans, that means the beginning of very difficult decisions. Some, like Miami, will begin investing in infrastructure, including sea walls, pumps, and other devices to keep the water at bay. Others may look at managed retreat, abandoning seafront communities and neighborhoods when the cost of fortifying, providing services, and constantly rebuilding is too much.

It’s not just about investing in protections such as sea walls, though estimates from the Union of Concerned Scientists suggest that by 2045, flooding accelerated by climate change will lead to $135 billion in property damage and force 280,000 Americans to adapt or relocate. Cities will grapple with numerous challenges that ripple out from the rising waters. How do you protect landmarks threatened by floods? How do you replace property tax revenue from lost waterfront property? How do you stem the tide of what many researchers and advocates have called “climate gentrification,” the displacement of poor communities by rich investors seeking the high ground? Where will climate refugees live? The increasing human toll of the climate crisis will require the federal government to quickly rethink how our system of flood insurance and community re-development funding is prioritized and disbursed, and will test how cities react to this slow-moving but accelerating crisis.

The increasing challenge of staying cool

The climate will clearly be the defining issue for the next decade of urban life. And rising temperatures may increasingly define where and when we can exist in the urban environment. Cities are experiencing more days of record-breaking heat, leading to long stretches of 100 degree–plus days in cities like Austin and historically rare heat waves in places like Northern Europe. Over time, as average temperatures continue to rise, this means more heat-related stress and illness, decreased foot traffic and economic activity at midday, and fewer hours for work. Cities like Phoenix are seeing activity shift to early mornings and nights as summers get hotter. The rhythm of life itself may begin to shift in response to hotter days and nights, meaning a corresponding shift in city services and operations.

Like so many of these changes, a rising thermometer means a rising threat of climate injustice. Historically disinvested communities—which already lack the parks, tree cover, and shade structures that can provide relief from hotter and hotter days—will suffer more and more from overheating and related health issues. Reducing carbon emissions to limit climate change is the most important step, but other aspects of urban design, such as installing reflective pavements and planting trees, need to be stepped up to help everyone cope with a future of blisteringly hot days.

Seniors in the city

One of the most significant demographic shifts, the silver tsunami of aging and retiring baby boomers and other generations will impact the nation at large, and cities in particular. By 2038, according to research by the Harvard Joint Center for Housing Studies, the number of households aged 70 to 79 will hit 10.7 million and the number of 80-and-over households is projected to reach 17.5 million, accounting for 12 percent of households in the U.S, 57 percent of which will consist of one person living alone.

This has big implications for cities. How will seniors access transit and healthcare services? Will they age in place and hold onto their homes longer, and if so, what happens when the affordable single-family housing stock isn’t passed down to the next generation? There’s also a huge income disparity among older adults who will be retiring in the future, presenting additional challenges to providing healthcare and social services.

Economic inequity, job concentration, and AI

Americans face extreme income inequality today. But perhaps even more worrisome is how economic inequality has bred spatial inequality. According to recent Brookings Institute research, in 2017 more than half of U.S. innovation jobs (defined as employment in 13 of the nation’s highest-tech, highest-R&D industries) were concentrated in just 41 counties. That has created a tale-of-two-cities situation, where metros such as San Francisco face skyrocketing costs of living, patently ridiculous real estate prices, and a crisis of displacement, affordability, and homelessness, which others in former industrial hubs, especially those in economically depressed rural areas, struggle to build stable, diverse, high-tech prosperity for all. It also explains the Amazon HQ2 debacle, as well as the current morass over Foxconn’s promised factory: Cities are desperate when it comes to attracting high-tech jobs, since many see it as the only game in town.

According to many experts, in the future, artificial intelligence (AI) may push even more workers out of their jobs, threatening even more inequality and make it more incumbent for cities to focus on economic development. Mark Muro at the Brookings Institution tells Curbed that while the economic advances and trends of the 2010s favored concentrated innovation districts in cities, and worked against manufacturing in rural areas, the coming age of AI will disrupt plans across the board.

“It is a city story,” Muro says. “While robotics and automation will be in small cities, AI is going to impact different types of jobs and professions, including those held by downtown office workers and millennial office staff, more urban professional services.”

Muro’s report doesn’t explicitly tie the rise of AI to job loss, only suggesting that it will disrupt many industries. But that means the fate of cities will be tied even more explicitly to their embrace of technology and equity; can investment in innovation and education create stable, high-paying, high-tech careers? ProPublica’s Alec MacGillis wrote recently that “growing regional inequality is the story of our moment.” Will cities be able to harness technology to reverse this trend?

Will the eyes in the sky found in Chinese cities go international?

The historically unprecedented growth of Chinese cities—as well as the impressive extension of mass transit and high-speed rail within and between them—was a defining story of the 2010s. The wealth and economic activity generated there reshaped wide swaths of the world economy, and will continue to do so. But another aspect of Chinese urbanism is also poised to rapidly spread: a high-tech melding of facial recognition, machine learning, cheap video cameras, and state-sanctioned surveillance.

As the New York Times and others have noted, Chinese leaders have built the most technologically advanced surveillance system in history, and not only are poised to expand it, but have also made big moves to export it. And before Americans and others in the West label this system dystopian, we should first look at ourselves and our own cities, and how a homegrown surveillance system is rapidly taking root.

Between facial recognition technology (which has been used in public housing), home security cameras such as Ring (which work very closely with law enforcement), and the melding of machine learning, computer vision, and commerce found in high-tech stores such as Amazon Go, the U.S. is also raising important civil rights questions. American cities may be the testing ground of whether these technologies will get implemented responsibly, with proper safeguards, or go unchecked.