Everyone who comes to southern California learns to be afraid of the Big One, the earthquake that will level everything. But even major tremors do not present such an immediate, visceral and terrifying threat as wildfires, which strike with shocking regularity and are getting worse.

This week's inferno, raging all the way from the Santa Barbara foothills to the Mexican border, has many immediate causes – notably, freakishly strong desert winds that have acted like a blowtorch on a region undergoing an unprecedented drought – but it is also part of a long-standing clash between natural weather cycles and the whims of human development.

"This is mother nature versus human nature," said Bill Patzert, a renowned climatologist with the Jet Propulsion Laboratory. "It's about too much development and too much fire suppression building up fuel over the past 50 years... In some ways this is the great war that will be fought here in the 21st century."

It has been four years since the previous devastating fire, which killed 23 people and destroyed thousands of homes in the same outer suburbs under threat now – on the mountainous edges of San Diego and the great Los Angeles metropolis. In Malibu, where this week's fires started with a couple of downed power lines, houses get torched every two to three years. Three times over the last century, the star-studded beach community has been consumed entirely.

The last time southern California underwent a significant pattern of drought and fire, though, it was the 1950s and the population of the region was no more than three million. Now the region is home to 20 million people – many of whom are building houses on the chaparral-covered hills and mountains where fire is part of the natural cycle.

This fire season has been at least three years in the making, ever since record rainfall in 2004 spurred a major growth in vegetation. That vegetation has been drying out ever since, because the record rain was followed by the worst drought. Last year, LA received less than five inches of rain, putting it on a par with Death Valley, five hours' drive away in the Mojave desert.

The region has been tinder-dry for months. Back in April, the largest area of public land in Los Angeles, Griffith Park, went up in flames, threatening the city zoo, the city observatory and the Hollywood sign, among other landmarks. Over the summer, though, the region largely dodged a bullet, with no major fires despite a continuing dearth of rain. If disaster was going to strike, this was the obvious time of year, because it is the beginning of the season when hot, dry desert winds known as Santa Anas blow in from Nevada and Utah. Usually, Santa Anas are mild and last a day at most. This time, they have lasted three days and gusted with the force of a minor hurricane – what Dr Patzert calls "Godzilla-sized" Santa Anas.

"The Santa Ana season goes through January and February," Dr Patzert said. "We're still super-duper dry. So this might just be a preview of coming attractions."

(By Andrew Gumbel, The Independent, 24/10/2007)