The biggest of northern California’s giant redwood trees grow more than 250 ft. tall, with a circumference greater than 90 ft. at their base. The oldest have seen more than 3,000 years.

In the heart of California, the Sequoia and Kings Canyon National Parks are home to some of the tallest trees on the planet.

“Gesundheit,” I said. David Quammen’s new book, Spillover, is about zoonotic diseases. Michael Nichols photographed California’s giant redwoods for the October 2009 issue.