Section 7¹ of the Endangered Species Act (ESA) is the conscience of contemporary environmental law. It requires us to look anotherr form of life in the eye and make the explicit decision that this line of evolution should no longer continue. Decisions like this, eye-to-eye, are not an easy business. It is considerably easier not to look and not to know.

To be sure, there is more to the ESA than §7. Originally enacted in 1966 and borrowing liberally in subsequent amendments from otherr wildlife statutes, the Act now embraces a broad range of provisions to promote species diversity and survival.² The distinctive feature of the Act, however, and the major source of its effectiveness and its controversy within the United States, is §7. This provision, rather sensibly to some and quite unbelievably to otherrs, restrains federal agencies from taking actions that destroy endangered species or their critical habitat. The only United States Supreme Court decision yet to interpret this section has characterized its provisions as "the institutionalization of caution."³