Vancouver, B.C., is North America's uncontested smart-growth leader: Among Northwestern cities, it has the greatest population density; the highest rates of cycling, walking and transit riding; and the fewest cars per capita. Its more than 2.3 million people have the highest life expectancy and the lowest teen birth and poverty rates. Ninety percent of Vancouver's power is hydroelectric, and the city regularly uses wind and solar. Its high-density neighborhoods (14,000 people per square mile) are clustered around high-rises, multifamily dwellings, restaurants, groceries, shops and parks, with wide sidewalks to encourage walking and short blocks that slow traffic. The extensive mass transit system includes high-capacity diesel buses, electric trolleys, light rail and an elevated train service. There are hundreds of miles of bike trails. As a result, Vancouver has the lowest per capita carbon emissions of any major city in the Western Hemisphere.

The Canadian metropolis didn't become an eco-friendly flagship by accident. Vancouver kept its neighborhoods intact and avoided the nightmare of suburban sprawl because it never built extensive freeways in the 1960s, when every other major urban area in North America was tearing up its central core. That wasn't because Vancouver's civic leaders had greater insight into the ultimate consequences of so-called urban renewal than their counterparts. In fact, bulldozers were eagerly revving their engines, ready to rip up significant chunks of the city.

A case can be made that it didn't happen, at least in part, because of a true butterfly effect: In the mid-1930s, Mary Lee Chan, a Chinese Canadian woman with a strong stubborn streak, refused to marry the man her father had selected. She was born in Vancouver in 1915, but her father decided it would be easier to raise his children in China because of persistent racism in Canada. After the family settled in Guang-dong Province near Hong Kong, Lee Wo Soon, as she was then named, fell in love with her teacher, Wah Goh Chan, and became a teacher herself – and refused the arranged marriage. "My grandfather believed girls should be educated because this was the way of the future, but he never expected this," recalled her daughter, Shirley Chan. "My mother was a strong personality and stood up to him even though it went against tradition."

After World War II, in the wake of the revelations about the Nazi atrocities, a chastened Canada repealed its Chinese exclusion laws. China was then in turmoil, torn by a civil war that would sweep the Communists into power in 1949. Lee Wo Soon returned to Vancouver, pregnant with Shirley, and worked three jobs, mostly in the garment industry, to save enough money to send for her husband and their eldest daughter. Wah Goh joined her two years later, barely escaping before the Red Army took over. They became Mary Lee and Walter Chan, putting down roots in largely Chinese Strathcona, the city's oldest residential neighborhood, settled in the late 19th century when Vancouver was a Wild West boomtown and the entry point for successive immigrant waves. While Mary continued her garment work, Walter juggled factory shifts and worked at the general store owned by Mary's father and brother – a social nexus where the close-knit Chinese community congregated and could buy imported goods from their native land.

But in 1959, a San Francisco-based consulting firm suggested building a network of freeways through the inner city, and Vancouver announced plans to raze vast swaths of Strathcona to make way for apartment buildings and a highway along the nearby waterfront. Newspapers heralded it as a much-needed slum cleanup that would revitalize the city's stagnant central business district. "The plan was to demolish the community in three phases – they would disperse the Chinese, who would be relocated to public housing projects, which would break up extended families and destroy natural communities, and then they would turn the land over to developers," recalled Shirley Chan. "When my parents first heard about the renewal program, they thought the government would get rid of the blight. 'Oh, good,' they thought, 'we'll just put more money into our house.' They even hired people to make repairs. But they didn't understand that their block was scheduled for demolition."

By 1965, more than 15 blocks had been leveled, displacing more than 3,000 mostly ethnic Chinese, who were warehoused in concrete high-rises on the city's edges. When the final phase began in 1968, with plans to flatten 600 more houses, the Chans faced eviction. "You can't stop it," Shirley, then a 21-year-old college student, told her parents. "The decisions have already been made." Undaunted, Mary Lee went door-to-door with a plastic shopping bag draped over her arm, dragging Shirley with her to translate, asking neighbors to sign petitions, join protests, and donate to a legal defense fund. The scholarly Walter, weakened by a genetic liver disease that would eventually take his life, stayed home and wrote a steady stream of articles for the Chinese language newspaper that rallied the community.

The Chans turned out to be formidable foes.

More than 800 people showed up at City Hall to protest. At a 1968 social planning department meeting, Mary and Shirley Chan met Darlene Mazari, who had been hired by the city to help people relocate. But when Mazari realized that these Chinese families were being robbed of everything they had worked for, she joined forces with them. The Chans' three-story Edwardian home quickly became the focal point for the Strathcona Property Owners and Tenants Association (SPOTA), which was founded that winter. Hundreds of people became involved. Many of them still didn't speak English and had once been too timid to take on the still very British and lily-white City Hall – but now, they organized fundraising events and lobbied local politicians.

Mazari recruited Mike Harcourt, then a 26-year-old storefront lawyer fresh out of school, to be SPOTA's pro bono legal advisor. "Shirley and Darlene told me, 'You've been hired to stop the freeway,' " he recalled. " 'You'll just be taking on the city government; the provincial government; the auto, oil, gas, and transportation industries; and the real estate developers. But other than that, don't worry about it.' "

Harcourt provided legal counsel to hundreds of elderly Chinese who had never before challenged authority, but were so incensed that they planned to stand in front of bulldozers and mobilize busloads of protesters. In the face of such intense opposition, the city capitulated, and Harcourt helped to negotiate the final agreement that led to the neighborhood's rehabilitation rather than its demolition. The fight swept progressives into political power, including Harcourt, who was elected to the city council in 1973, then became mayor in 1980, and later premier of British Columbia. Shirley Chan served as his mayoral chief of staff for more than five years – the first woman in Vancouver history to hold that position – and went on to a four-decade-long career in public service. Walter died at age 67 in 1973, while Mary Lee lived almost three decades more, until 2002. She remained active in her community well into her 80s, but never remarried. The Canadian government has designated the Chan House, at 658 Keefer Street in Strathcona, a historical site.

Their against-all-odds victory was the catalyst for many changes, including completely revamped zoning regulations that allowed housing, restaurants and shops in the city's downtown, not just office buildings, and the creation of a central area plan that transformed old industrial sites into thriving residential communities like False Creek North and Coal Harbour, former rail yards and shipping centers on the Vancouver peninsula. Today, Coal Harbour, a centrally located neighborhood within walking distance of downtown and Stanley Park, offers magnificent vistas and a waterfront park. False Creek North, a high-density community of about 50,000 residents, was an Olympic Village for the 2010 Winter Games athletes and boasts both a soaring steel-and-glass municipal science center and a popular boat marina.

"The Strathcona Property Owners and Tenants Association is the single most significant reason why Vancouver is such a profoundly livable city today," recalled Harcourt, who recently coauthored City Making in Paradise: Nine Decisions That Saved Vancouver. "It was our turning point – otherwise Vancouver would have been another failed city with an elevated freeway that would have wiped out two heritage areas and split and scarred three neighborhoods, and the central business district would be another sterile place that emptied out at 5 o'clock. We became ground zero of a whole different way of looking at what a city can and should be, and initiated the notion of citizen engagement and livable cities, rather than the old and now discredited urban model that chased people out of perfectly good neighborhoods and created dead downtowns."

This essay was excerpted and adapted from Fevered: Why a Hotter Planet Will Hurt Our Health and How We Can Save Ourselves (Rodale, 2013).

A former Los Angeles Times staff writer, Linda Marsa is a Discover contributing editor and has written for Parade, Popular Science and Pacific Standard, among others. Her work was included in Best American Science Writing, 2012.