Folk singer Joan Baez delivered a surprise serenade to two environmental activists who have spent months perched in towering redwoods owned by Pacific Lumber Co.

"Air a little thin up there?'' Baez shouted to the protesters, who were more than 150 feet above the ground. She then began singing, "Ain't going to let nobody push me around, gonna build a brand-new world.''

The two activists are protesting Pacific Lumber's plans to harvest timber in the area. They complain the logging plans threaten old-growth redwood trees and the health of forest ecosystems.

Baez, whose hits include "The Night They Drove Old Dixie Down,'' was in the area for two shows at Humboldt State University.

The 61-year-old singer dropped by Monday to offer her support. She made a similar visit to Humboldt County in 1999 to meet Julia "Butterfly'' Hill, who spent two years in a redwood she dubbed "Luna."