The next manifest destiny

Photo by Vincent Laforet, National Geographic Magazine

It's beginning to look as though the spectacular economic boom in America's arid west - the golf courses in the desert, the huge dams, the miles and miles of tract housing, the strip malls with palm-and-lawn landscaping - coincided with the wettest century of the past millennium, according to an article by Robert Kunzig in the latest National Geographic Magazine.

So now things are getting back to normal, which is way too dry for the West's new arrivals: Lake Powell is half empty and wildfires in suburban subdivisions have become an annual event. The alfalfa farmers in the desert are getting militant. Your southwestern country clubs are getting nervous.

The West's recovery from the past century's bout of relative dampness is actually likely to go speeding right past "normal" and enter into a few centuries' worth of mega-drought, thanks to effects of global climate change that are already taking hold. The warming globe is baking the moisture out of the air in the world's desert regions and making their climates even drier, even as it relocates that moisture north to wallop more temperate latitudes with increased precipitation and more powerful storms.

In Western mountains, which typically attract enough moisture to sustain forests, increased heat and drought and decreasing snowpack are exposing forests to more and more wildfires, while the trees that don't burn are left to contend with exploding infestations of pine beetles and other pests. The West's sky islands, isolated remnants of ice-age ecosystems that survive high up in desert mountains, are retreating further uphill every year as their forests seek the cooler air they need to survive. Like spruce-fir forests in New England, most of these ecosystems will shrink to nothing when they reach the summits of their mountains.

A landscape ecologist for a federal land agency says that "the projections are that Joshua trees may not survive in Joshua Tree National Park. Sequoias may not survive in Sequoia National Park. What do you do? Do you irrigate these things? Or do you let a 2,000-year-old tree die?"