"I'm just one woman, and the developers have great power. If they want to squash you, they can."

Her name is Norma Sánchez, and she founded Angels of the Estuary, a grassroots organization that opposed the digging of a marina near San José del Cabo by Vaughn's Grupo Questro. It was dug anyway, part of the $1-billion Puerto Los Cabos development now in full swing. A bridge being built just upstream of the San José Estuary will bring the expected tourists and residents to four planned communities and what resembles a giant, boat-filled keyhole punched into the desert's green verge, where crops were formerly grown. The marina has berths for 400-plus boats, including, according to the website, "luxury mega yachts," and will have the usual suspects: golf courses, hotels, spas, beach clubs, condos.

Many of the town's former residents have sold out and moved to the outskirts, or away, as Sánchez has. Her soft brown eyes, under the brim of the straw hat, belie determination but also a touch of fatigue. She's been sobered by the loss of her particular development battle to a well-oiled legal machine and what she considers the government's inability, and unwillingness, to monitor the rising tide of concrete.

"There are better ways to build than by disrupting whole towns, using up a lot of scarce water, and creating huge waste issues. Why can't developers understand that they can still make money if they do the right thing environmentally?"

We're walking across a blindingly white beach on the west side of the estuary, through what amounts to a living mirage: fresh water, dense marsh grass, gallinules and other aquatic birds, and a distant row of palms that seem to sway in the rising thermals. "This is a very important place," she says. "It has fresh water where that's rare, and provides habitat for waterfowl and many other species," including people.

The effect of saltwater let in by the nearby marina is still an open question. Baja's small but tenacious Mexican Center for Environmental Law up in La Paz assisted Sánchez in opposing it, and several international organizations weighed in, among them Greenpeace, whose activists chained themselves to heavy earthmoving equipment in 2006 in an unsuccessful attempt to prevent the marina dig.

The marina, and Puerto Los Cabos, had the early backing of the Mexican government's Fonatur (National Fund for the Development of Tourism), the powerful agency that identifies potential tourist spots and provides infrastructure, all at public expense. These projects are then handed over to the private sector, part of a strategy that has produced some economic benefits for the country but also led to social and environmental problems like those in woefully overbuilt Cancún and other well-worn tourist venues. "Fonatur," says Sánchez, "is a partner in all these developments."