I AGREE, AND I SHOULD confess that I'm not exactly neutral. As someone who resides in the West, I don't see conservation as an abstraction. I live in Missoula, Montana, downriver from the nation's largest cluster of Superfund sites, and when I hear that obstruction in Washington has further delayed their cleanup, I get angry. I worked for ten years as a river guide and Outward Bound instructor in the Utah canyons, and when President Bush relaxed regulations for gas exploration, I watched the results up close: 32-ton thumper trucks stomping a landscape that said more about God than a thousand cathedrals. After that I moved east to work for Howard Dean's presidential campaign. We all know how that turned out.

So when I began following Mark and Tom Udall, I hoped they would fill their fathers' shoes. An unfair expectation, perhaps, but such is the downside of being born into a dynasty. I wanted them to rise up and lead—partly because I liked their politics and pedigree, but also because at a time when environmentalism has been sequestered in big coastal cities, I think its next wave of leaders has to come from the rural West. It will never get anywhere—and didn't for years—without support in the states whose resources and landscapes inspired the whole idea of conservation in the first place.

The Udalls epitomize that western ethic. "Stewart and Mo had a land connection," Randy Udall told me. "They grew up in this rural conservative Mormon community, and they got this stuff at some sort of visceral level. If you're not connected in a primal, natural way with the land, then you're gonna screw up."

Mark and Tom aren't the only ones in the current crop of Udalls to work in conservation. Randy's nonprofit, CORE,cooperates with local government to promote renewable energy and enact green laws. Another brother, 50-year-old Brad, a former Grand Canyon boatman, is director of Western Water Assessment, a joint program of the University of Colorado and the National Oceanic and Atmospheric Administration.

Though the best-known Udalls have been staunch Democrats, the family has a Republican side. The split dates back to the days of Mormon polygamy—and the three wives and 15 children of David King Udall. His first wife, Eliza, gave him nine children, including Levi, a Democrat who became chief justice of the Arizona Supreme Court and fathered Stewart and Mo. His second wife, Ida, had six kids, including Jesse, a Republican who succeeded his half brother as chief justice and whose grandson is Gordon Smith, a two-term Republican senator from Oregon. Unlike his cousins, Smith is a practicing Mormon. He has turned out to be a conservationist himself, defying his party on key environmental issues like ANWR. "When Gordon voted against drilling," Mark told me, "I sent him a note that said, 'My dad would be proud.'"

I wanted to meet the last member of that storied generation, so in April I traveled to Santa Fe, New Mexico, to see Stewart Udall. At 88, the patriarch has a full head of silver hair and a glint in his eye. "I've been a pretty hearty type," he said, tapping his cane, when he met me at the door of his hillside adobe home. That was a bald understatement. Though he'd broken his hip over the winter, three years earlier he'd rafted through the Grand Canyon and hiked out. He lost his wife, Ermalee, in 2001, and has lived alone since, next door to Tom and his wife, attorney Jill Cooper.

It was a clear spring day; through the living-room window, we watched the sun drop. "I grew up about 300 miles over there," Stewart said, waving toward the horizon in a casual way that made me think he hadn't strayed too far in his mind from St. Johns, Arizona, the dusty town on the Little Colorado River where his grandfather settled. Stewart had been a Mormon missionary, an Air Force gunner in World War II, and a U.S. representative. During his term at Interior, the National Park Service added Canyonlands and three other parks, six monuments, nine recreation areas, 20 historic sites, and 56 wildlife refuges. He also found time to write a book, The Quiet Crisis, debunking the "myth of superabundance," that Old West idea that we could never deplete our water, trees, and minerals.

Which isn't to say he was on the green side of every debate. "The Udalls come out of an ethic that is very Old Testament," Gordon Smith told me. "If they didn't divert rivers and irrigate fields, they died."

Early on, this notion led Stewart and Mo to support massive engineering projects like Glen Canyon Dam, the Central Arizona Project (a 336-mile aqueduct that diverts the Colorado River), and even dams in the Grand Canyon. But their positions evolved in the late sixties, reflecting a national shift of values triggered in part by the Sierra Club's protests against dams on the Colorado. After a family float trip through the Grand Canyon in 1967, Stewart used his influence to kill the dams.

"I presented [the Central Arizona Project] in four different Congresses as a way to rescue farmers," Stewart told me, his voice rising. "Farmers were going to get all the water. Then the bill passed—and this whole sprawl! Phoenix is trying to be another Los Angeles, and the longer it goes on the more it makes me sick."

Stewart is alarmed about the state of the environment today, particularly global warming, and he's not optimistic about Congress's ability to stop it. In his day, he said, conservation wasn't as partisan, and many of its proponents were Republicans. "Then we hit a stone wall with Reagan," he said. "And the current president has been the worst in our nation's history in terms of conservation. Mark and Tom were on the committees, but what could they do? You have to have executive leadership."