For Petra Berschin, a bookstore owner in Heidelberg, Germany, the fight against climate change begins at her doorstep—literally. Berschin lives in Heidelberg’s Bahnstadt district, one of the world’s largest carbon-neutral neighborhoods. Home to 6,500 residents, Bahnstadt is a model for sustainable urban living, with every building—public and private—designed to strict energy efficiency standards. Thanks to highly insulated structures, the average Bahnstadt building uses 80% less energy for heating than buildings in other districts in Heidelberg, according to the city. By some estimates, the homes in the district emit just 0.13 metric tons per resident for energy use annually—significantly below Heidelberg’s citywide average of 2 metric tons.

Bahnstadt is one of many neighborhoods around the world organizing to fight carbon emissions at the grassroots level. As of November 2024, 145 countries have announced or are considering net-zero emissions targets, covering nearly 90% of global greenhouse gas emissions, but they are subject to changes in leadership and priorities. Neighborhoods, on the other hand, can persevere through changing political tides and experiment with novel approaches to lowering emissions. So far 22 cities have joined the global carbon-neutral cities alliance. 

In Bahnstadt, climate consciousness is a way of life. Berschin, 55, cycles or walks for errands and has introduced eco-friendly practices in her bookstore, from energy-efficient lighting to sustainable wrapping materials. “The climate crisis is the defining issue of our time,” she says—a sentiment shared across the neighborhood.

The community’s infrastructure reflects this commitment. Over 3,000 smart meters track energy usage, while two-thirds of rooftops are covered with greenery to reduce urban heat and manage stormwater. A network of bike paths and a tramline connects Bahnstadt to the city center, minimizing car dependency.

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Bahnstadt’s success draws on the lessons of Germany’s “smart cities,” a movement born in the early 2010s when urban planners began consolidating data to inform planning decisions. Cities began collecting real-time data, and lots of it. The implications for climate advocates were revolutionary. For the first time, neighborhoods could not only measure and visualize their carbon emissions but also advocate for change using a language that no one could ignore: hard numbers.

“Every citizen can better engage in designing a joint vision and now knows where we want to go together and what [they] can personally do to contribute to meeting those goals,” says Matthias Woiwode von Gilardi who led Germany’s Smart Cities Coordination Office. Over the last five years,the country increased the number of smart city projects sixfold to over 400. “Neighborhoods have the benefit of being smaller, where things can be piloted and tested in a more controllable system, in which causal effects can be better identified.” These “regulatory sandboxes” as he calls it, allow officials and residents to evaluate what works and can scale elsewhere.

Across the Atlantic, a neighborhood suffering from surges of rainfall and flooding was stepping into a sandbox of its own. Bordered by a landfill to the southeast and Interstate 94 to the north, the Bryant community of Ann Arbor, Mich., was an unlikely candidate to become a trailblazer in carbon neutrality. But the working-class community of 262 single-family homes is on track to be America’s first carbon-neutral neighborhood, according to the city government. Just three years ago, Bryant was what city planners call energy-burdened. Many residents lived in houses with poor insulation, and utility bills consumed up to 30% of their incomes, according to city officials.  An outdated drainage system could not cope with the now frequent bouts of rain, leading to constant flooding.

But Derrick Miller, executive director of Community Action Network which manages the Bryant Community Center, saw these obstacles as an opportunity. In 2020, when the city of Ann Arbor announced it wanted to achieve carbon neutrality by the end of the decade, Miller offered Bryant as a starting point. “We landed on the Bryant neighborhood not because it would have been easy but because it would be difficult and complex. We wanted experiences that would be transferable to other communities,” he says.

Read more: Climate-Proof Towns Are Popping Up Across the U.S.

The transformation began with door-to-door visits to assess energy usage. Using local and federal grants, contractors upgraded insulation, replaced windows, installed solar panels, and introduced geothermal energy systems to reduce household carbon emissions one by one. Miller and his team transformed the community center into a learning lab for residents to understand how to use the new technologies in their homes.

As households witnessed their utility bills drop—sometimes by nearly 90% according to Miller—word spread that the people going door to door were here to help. “There’s that snowball effect,” he says. “What we thought was crazy just three years ago is absolutely doable.”

While the projects that work in Bahnstadt or Bryant aren’t transferable to every community, their influence extends beyond neighborhood borders. “The way we think about our impact is less about scale and more about spread,” says Rafael Robles, a developer in Chicago. Robles’s company, Duo Development, created a co-working space in one of the city’s poorest neighborhoods of North Lawndale after listening to neighbors’ requests for places to work that don’t require expensive, environmentally-unfriendly commutes to other parts of the city. The complex, which hosts workshops and exhibitions, is inspiring developers and residents to reconsider the neighborhood as a target for sustainable investment. “Some of these small-scale efforts are going to be really important because they set a new precedent,” he says. “We want people, including the residents who live here, to see it and say, okay, I can do that too.”

Neighborhood initiatives also show residents that going carbon neutral doesn’t have to equal deprivation. In fact, it can result in a quality-of-life upgrade. Felony and Cory Mewton remember the day the community center representatives in Bryant knocked on their door last year. The home they had lived in for 12 years used to take hours to cool in the summer, leaving them sweltering in the heat.

“If someone has a solution, I’m willing to give it a try,” says Felony. The Mewtons agreed to renovate their home to lower its emissions, and within a year, contractors encapsulated their crawl space, upgraded insulation, and installed a new furnace—at no cost to the family. So the Mewtons did what any good neighbor would do. They talked about it. “People thought it was too good to be true, but we knew it was legit, so we told them and tried to get them on board.” As the news circulated, more neighbors wanted to keep up with the Mewtons. 

To date, the Bryant Community Center has facilitated upgrades for 40 homes, with another 30 households waiting their turn. It also secured enough funding to lower emissions in an additional 100 homes in the neighborhood. In the end, proximity proved essential to convincing the most skeptical residents. “If there’s a problem, they know where to go,” says Felony. “There’s always someone to talk to, and they’re never far away.”