5 big ideas for fixing global cities’ most daunting challenges

This article is part of a Fortune Special Report on Rethinking the City.

Cities are complex organisms, which means no aspect of urban life operates in a vacuum. Systems are interdependent, problems tend to have multiple causes, and potential solutions are usually multi-faceted, too.

Fortune spoke with a range of experts, specializing in housing, urban design, transportation, and more. We asked what they see as the biggest challenges facing our largest metropolises, and how they believe these problems can be solved.

Their answers probe the past to anticipate the future—and look around the globe to find possible solutions. And indeed, no matter how seemingly insurmountable the problem, chances are that somewhere in the world, there’s a city that’s making strides toward fixing it.

The problem: outdated tech

The solution: As the amount of data urban centers produce, capture, and rely on to guide public policy continues to mushroom, it’s time to rethink cities’ approach to software, says Ben Cerveny, president of the Foundation for Public Code. Most are either trying to build their own—despite limited resources and expertise—or relying on third-party products they don’t know how to, or can’t, adapt or update. One solution: sharing tools with one another; he cites Barcelona’s Decidim, a platform for involving citizens in decision-making, as an example. Cerveny also advocates for an open software-development process. Not only does going open-source offer cities access to fresh ideas, he says, but it helps policymakers better understand the software itself. After all, says Cerveny, “software will almost always be the way that policy is implemented in the future.” —Lydia Belanger

The problem: climate change

The solution: The idea that there’s any single way to fight climate change is part of the problem. In reality, the effects are already unfolding, and cities must make a variety of “tough choices around where, what, and who to protect,” says Jonathan Woetzel, leader of McKinsey’s Cities Special Initiative. He points to India’s national cooling plan as a model; in addition to attempting to cut emissions, it promotes “cool roofs” and other building changes designed to make high temperatures more bearable. Cities will also need to create policies that encourage citizens to change their behavior to adapt to new climate realities, he says (think shifting school vacations). And bigger metropolises must share best practices—and financial resources—with their smaller neighbors, says Woetzel: “We have to collaborate to meet these challenges.” —Emma Hinchliffe

The problem: inefficient buses

The solution: Buses, which are cheaper and less complicated for cities to install than trains, are an essential aspect of public transportation, yet ridership is declining. In the U.S., for example, bus commutes dropped 11% from 2000 to 2018. To get more butts in bus seats—and more cars off the road—a 2018 study from McGill University researchers finds that cities must reverse the current trend of shrinking bus service and routes. A more futuristic fix: electric buses, which are quieter, more comfortable, and, most important, more eco-friendly, says Institute for Transportation and Development Policy spokesperson Jemilah Magnusson. In Shenzhen, China, the fully electric fleet of more than 16,000 buses has reduced annual CO2 emissions by 1.4 million tons, according to the ITDP. For more, see our story on Shenzhen in this issue. —L.B.

The problem: lack of affordable housing

The solution: There is not a single U.S. city where a full-time employee earning minimum wage can afford to rent a two-bedroom apartment, according to the National Low Income Housing Coalition. While employers like Amazon and Microsoft have taken steps to tackle the issue, Affordable Housing Institute CEO David A. Smith thinks there’s potential for business to pitch in on a far larger scale. He points to the Community Reinvestment Act of 1977, which pushed banks to provide more credit to local low- and moderate-income borrowers. A similar law aimed at encouraging employers to provide funding for housing development could have a huge impact, he says, “provided it’s enacted collaboratively with industry.” —L.B.

The problem: urban isolation

The solution: Society is battling a “loneliness epidemic,” says former U.S. Surgeon General Vivek Murthy, and urban sprawl is a major contributor. Three-quarters of the residential land in most cities is zoned exclusively for detached, single-family homes, says Ellen Dunham-Jones, director of Urban Design at Georgia Tech School of Architecture. And when cities do build apartment buildings, they tend to be massive in order to maximize efficiency, she says. The catch: Both building styles leave residents isolated and, often, anonymous to neighbors. To build urban connections, planners are increasingly looking to retrofit unused industrial spaces like parking lots and loading docks into shared spaces, says Dunham-Jones. An example: Tulsa turned a polluted former trucking depot into a park and an area for community activities that draw about 3,000 people a week. —L.B.