EVERY HILL A THRILL: The Imperial Sand Dunes Recreation Area attracts increasingly large crowds of off-roaders seeking roller-coaster-style excitement on the near-vertical drifts of the largest dunes in North America.Land battle heats up dunes By Daniel B. Wood GLAMIS, CALIF. – When they look out across the largest sand dunes in North America, Jeneiene and Daniel Patterson see paradise. The 45-by-15-mile sprawl of granulated humps is a botanical Eden. Ironwood, smoke trees, and desert buckwheat provide a happy, if hot, habitat for flitting songbirds, darting lizards, stalking puma, and lumbering tortoises. "This is a biological wonderland," says Mr. Patterson, a...