If a tree falls in a forest and no one is around to hear it, does it make a sound?

The answer is yes, if it happened in New Mexico's Jemez River Basin on June 26, 2011, at 1 p.m. local time.

The tipping of one tree as it creaked and fell hinted at a crackle soon to come, a fast-burning wildfire. Ultimately, the fire blazed through a large part of a 1.5 million-acre national forest.

On the day the fire started, strong, unpredictable winds blew through the trees, rustling leaves and creaking dead wood. Perhaps in a gust, a lone tree fell. On the way down, it took out a power line and sparked a fire that, by high noon the next day, had burned 43,000 acres, an acre every two seconds.

At sundown that next day, the Las Conchas fire, as it came to be called, still ran wild. The toll had climbed to more than 61,000 acres of forest. Egged on by north winds, it jumped the trails of the Pajarito Mountain ski area. Then it turned and raged south, threatening the town of Cochiti, N.M.

Within four days, it had singed more than 103,000 acres, making it the largest fire in New Mexico history at the time.

The forest and the watershed--the critical zone--left behind ...

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