“Save the World” is a bit of a cliché in tech. This is because we try to use design to mitigate the inefficiencies that limit how directly we can address our problems. Cities can actually be approached in the same way. When the aggregate of our individual actions causes problems, the behaviors we facilitate through design are extremely important. When we build cities that encourage environmentally degrading behavior, the impact is substantial.

In 1950, the population of San Francisco was 775,357. In 1990, it was 777,360. At first glance, one might conclude that San Francisco didn’t grow during that time, but this is just an illusion. San Francisco proper may have grown by only 0.2%, but the nine-county Bay Area grew by almost 90%, from 3,638,939 to 6,783,760. The majority of this growth has been in areas we know today to be suburbs, but our elders remember as pastures, farmland, orchards, and natural open space. We’ve spent the past half century growing outward instead of inward and upward, and this is a problem.

Source: US Census. “Suburban Bay Area” is defined as the 9-county Bay Area except San Francisco, Oakland, and Berkeley.

This pattern of development is fundamentally unsustainable. Urban dwellings, with smaller interiors and shared walls, need less energy to heat and cool than single-family homes because they bleed energy less into the surrounding air. This means less power usage per resident. What’s more, the suburban Eastern and Southern Bay Area today are less temperate than the urban core, even before accounting for development patterns. Antioch, CA, which grew by roughly 60% between 1990 and 2010, has an average July high of 91.1 degrees, and an average December low of 37.4. As a result, energy usage is naturally far higher per-resident than in the milder San Francisco and Oakland. That natural disadvantage is then made worse by Antioch’s single family homes that lose energy through all four exterior walls plus the roof. A San Francisco or Oakland apartment cozies up with its neighboring units, retaining more energy.

Suburban development looks even less sustainable when you consider transportation habits. Urban environs facilitate transit use, but suburbs are ill-suited to high-capacity transit. By the virtue of their low density, you have fewer people traveling between more arbitrary points. In low-density developments, people travel further to complete the same tasks. UC Berkeley finds that urban areas of San Francisco and Oakland have as little as ⅓ the carbon emissions per resident compared to places like Antioch. When people live in low-density areas, the result is inevitable: more driving, and by extension, more carbon emissions. If we want to get people out of their cars, we need to stop suppressing how many people can live in cities.

In the same way that the urban Bay Area is greener than the suburbs, the entire California coast holds the same advantages over to the sprawling and booming metropolitan areas of America’s Sun Belt. Cities like Phoenix, Las Vegas, and Dallas have a significant advantage in attracting workers because they offer relatively affordable housing. These cities have adopted a suburban, decentralized development strategy, with few restrictions on outward growth. Although they accommodate population growth with enough housing construction to keep prices in check, they do so in a way that’s unnecessarily taxing on the environment. If we want to make green living attractive to all Americans, we need to price it competitively.

The artificial suppression of urban housing in the Bay Area drives up prices, limiting our region’s ability to absorb more population, and forcing potential residents to live in less environmentally sustainable alternatives. Anti-growth urban policies are a deterrent against sustainable living.

Suburbanization is the environment’s greatest threat, and as America’s population continues to grow, we must stop discouraging its alternatives. This necessarily means making room for new residents in the few cities that have the right tools to enable a sustainable lifestyle. The Bay Area prides itself on its stewardship for our planet, and if we want to be taken seriously, we need to put our money where our mouth is. We need to overhaul the regulatory systems that artificially suppress sustainable development. When people from elsewhere ask us if there’s any room here for them to come live the same green lifestyle as us, we owe it to ourselves, our neighbors, and the planet to say “Yes.”