A redwood tree grove at Roberts Regional Recreation area in Oakland, California. | Smith Collection/Gado via Getty Images A grove of coast redwood trees is a forest of forests. Individual trees can live for thousands of years, and as they grow, their canopies develop mats of soils and ferns, creating something like a second forest floor hundreds of feet above the ground. These elevated ecosystems are home to creatures like the wandering salamander, which can spend its entire life cycle on top of a single tree, and the marbled murrelet, a seabird whose nesting habits were a mystery unt...