Book excerpt: A new vision is sweeping through ecological science: The dense web of dependencies that makes up an ecosystem has gained an added dimension-the dimension of time. Every field, forest, and park is full of living organisms adapted for relationships with creatures that are now extinct. In a vivid narrative, Connie Barlow shows how the idea of "missing partners" in nature evolved from isolated, curious examples into an idea that is transforming how ecologists understand the entire flora and fauna of the Americas. This fascinating book will enrich and deepen the experience of anyone who enjoys a stroll through the woods or even down an urban sidewalk. But this knowledge has a dark side too: Barlow's "ghost stories" teach us that the ripples of biodiversity loss around us now are just the leading edge of what may well become perilous cascades of extinction.