Ebb and Flow: Tides and Life on Our Once and Future Planet is well titled. It tells the story of tides, why they matter, what causes them, and how they have changed over time. The author, Tom Koppel, is not an analyst or theoretician of tides but a man of inquisitive mind and substantial beachcombing and sailing experience. He tells his stories in an engaging style, be they of gathering clams on tidal flats or harrowing escapes from tidal races. They are woven into a well-paced and thoughtful narrative, never straying far from the tidal theme. Most of the chapters combine two elements-typically, a story of how tides have played a denning role in the lives of a coastal people, and a discussion of the related natural history. For example, Chapter 9 begins with the story of how certain coastal Native Americans harvest a small fish (eulachon), describes the involvement of tides, and then broadens the discussion to include tides in coastal ecosystems generally. This format suits the topic well, successfully drawing in the reader and maintaining interest.
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