The Endangered Species Act (ESA) has a stated purpose of conserving species identified as endangered or threatened with extinction, and conserving ecosystems on which they depend. It is perennially controversial because the protections provided can make it the visible policy focal point for underlying situations involving the allocation of scarce or diminishing lands or resources, especially in instances where societal values may be changing. In response to past controversies, Congress has repeatedly considered minor amendments and major changes to the act. This book describes the major features and controversies of the ESA as background for consideration of possible amendments in the 113th Congress.