"Driftwood, wood carried by water from the forest to the sea, is a critically important source of habitat and food for the marine ecosystem, including the deep-sea floor. Even during its seaward journey, driftwood is both habitat and a source of food for a multitude of plants and animals, both aquatic and terrestrial. In addition, some driftwood controls stream velocities, stabilizes stream banks, makes waterfalls and pools, and creates and protects fish spawning areas. Other driftwood protects the encroachment of vegetation on floodplains and allows forests to expand... The natural processes by which wood disappears from streams and rivers have positive effects on the ecosystem. Human activities, on the other hand, such as cleaning streams, logging, and firewood cutting, have had negative effects..."--Preface.