In his most recent book, Collapse: How Societies Choose to Fail or Succeed, Jared Diamond examines the rise and fall of civilizations ranging from Easter Island in Polynesia to the pre-Columbian Mayan and Anasazi. All of them faced a similar combination of problems: climate change, rapid population growth and resource depletion among them. And all of them failed to rise to the challenge, because they were more or less rigid societies unable to adapt when change became necessary.

It’s a long, fascinating read, even when the Pulitzer-prize-winning author stretches to connect the lessons learned in these ancient schools of hard knocks to the problems facing the West today. He devotes a whole chapter to southwestern Montana, his current home, delving into issues High Country News readers know by heart — the demise of agriculture, mining and logging, the deterioration of native forests and grasslands, the rise of the class-splitting amenity economy.

Montana may seem an odd choice, as Diamond says, with an environment and economy that hardly seem on the brink of collapse. But early stress signs are visible, he warns, not the least of which is the state’s heavy reliance on government subsidies and outside wealth; more than half of Montana residents’ income doesn’t come from their work in the state.

"If Montana were an isolated island, as Easter Island in the Pacific Ocean was in Polynesian times before European arrival," Diamond writes, "its present First World economy would already have collapsed, nor could it have developed that economy in the first place."

It’s a thought-provoking perspective. Still, I wish Diamond had chosen another Western state to make his case, one more obviously under stress — such as Arizona, the subject of this issue’s cover story. As HCN correspondent Matt Jenkins writes, Arizona’s population has zoomed from 3.6 million to more than 6 million since 1990; demographers predict another doubling by the year 2055. The majority will live in the Phoenix area, which receives a scant seven inches of rain a year.

It sounds like the perfect recipe for a Diamond-style "collapse": a rapidly growing desert megalopolis with an economy centered on the construction of more than 45,000 new homes every year, many of them on former prime agricultural lands. But, as Jenkins notes, most of Phoenix’s business and political leaders believe this boom can continue indefinitely.

The key to their confidence is the Central Arizona Project, which sends Colorado River water to Phoenix and Tucson. A drought in Arizona — even one as severe as this winter’s — is of little account as long as the CAP canal brims with Rocky Mountain snowmelt, and as long as the farmers and tribes who own much of that water are willing to sell or lease it.

Phoenix’s boosters are likely encouraged by the way the West has endured the severe drought of the past several years. During the summer of 2002, for example, Denverites willingly dried up their lawns and public golf courses, saving more than enough water to get by and demonstrating that the region still has plenty of slack in its water-supply systems.

So why should we worry? Well, as Diamond says, unforeseen bumps in the road can quickly upset a society’s fortunes, no matter how wealthy and optimistic that society is. A deepening of the drought in the Colorado River Basin, or an international conflagration that cuts off vital supplies of fuel or food, could shrivel up Arizona’s boom in a hurry, turning all those new subdivisions into ghost towns.

Few of us like to plan for the worst. But we should do it anyway. As Jared Diamond says, successful societies are the ones that have "the courage … to make bold, courageous, anticipatory decisions at a time when problems have become perceptible, but before they have reached crisis proportions."

In the West, that time is now.