STEVE KLINEBERG, a sociologist at Rice University, mentions a couple of events that made Houston’s leaders take notice of a looming problem. One was the day, in 1999, when their city overtook Los Angeles as America’s most polluted—evidence that the rise in asthma attacks among the city’s children, and the students passing out on football pitches, were no coincidence. Another was when Houston came up short in its bid to compete to host the 2012 Olympics. No one on the United States Olympics Committee voted for it, despite the fact that Houston had a brand-new stadium and had promised to turn an old sports field into the world’s largest air-conditioned track-and-field arena.

At a casual glance, Houston looks much as it ever did: a tangle of freeways running through a hodgepodge of skyscrapers, strip malls and mixed districts. A closer inspection, though, shows signs of change. The transport authority, which branched into light rail in 2004, is now planning three new lines, adding more than 20 miles of track. Most of the traffic lights now boast LED bulbs, rather than the incandescent sort. More than half the cars in the official city fleet are hybrid or electric, and in May a bike-sharing programme began. Every Wednesday a farmers’ market takes place by the steps of city hall.

Other changes are harder to see. The energy codes for buildings have been overhauled and the city is, astonishingly, America’s biggest municipal buyer of renewable energy; about a third of its power comes from Texan wind farms.

Houston, in other words, is going green. Laura Spanjian, the city’s director of sustainability, says that businesses are increasingly likely to get on board if they can see the long-term savings or the competitive advantages that flow from creating a more attractive city. She adds an important clarification: “We’re not mandating that they have to do this.” That would not go down well. Houston is the capital of America’s energy industry, and its leaders have traditionally been wary of environmental regulation, both at home and abroad.

In fact the city has been sceptical of regulations in general, and even more of central planning. Houston famously has no zoning, which helps explain why the city covers some 600 square miles. It is America’s fourth-largest city by population, but less than half as densely populated as sprawling Los Angeles. People are heavily dependent on cars, the air quality is poor and access to green space is haphazard. At the same time, Houston has jobs, a low cost of living and cheap property. Many people have accepted that trade-off. Between 2000 and 2010 the greater metropolitan area added more than 1.2m people, making it America’s fastest-growing city.

Still, the public is taking more interest in sustainability, and for a number of reasons. As the city’s population has swelled, the suburbs have become more crowded. Some of the growth has come from the domestic migration of young professionals with a taste for city life. And despite living in an oil-industry hub, the people of Houston are still aware of the cost of energy; during the summer of 2008, when petrol prices hovered around $4 a gallon, the papers reported a surge of people riding their bicycles to bus stops so that they could take public transport to work.

The annual Houston Area Survey from Rice’s Kinder Institute also shows a change. This year’s survey found that 56% think a much better public transport system is “very important” for the city’s future. A similarly solid majority said the Metro system should use all its revenue for improvements to public transport, rather than diverting funds to mend potholes. In the 1990s, most respondents were more concerned about the roads.

People’s views about houses have changed, too. In 2008 59% said they would prefer a big house with a big garden, even if that meant they had to use their car to go everywhere. Just 36% preferred a smaller house within walking distance of shops and workplaces. By 2012, preferences were running the other way: 51% liked the idea of a smaller house in a more interesting district, and only 47% said they wanted the lavish McMansion.