Trees are living chronometers of the environment, faithfully recording histories of climate and forest disturbances in the properties of their annual rings. Worldwide, thousands of chronologies have been developed, extending unbroken for hundreds or even thousands of years. Beyond trees, a wide range of aquatic organisms including fish, bivalves, corals, and even some marine mammals form annual increments - and can be surprisingly long-lived. Members of several fish species have been aged at more than 100 years while at least one species of marine clam lives to be more than 500.
