being the sacred capital of the Cherokee Nation as early as the 16th century and the latter providing the linguistic basis from which the State of Tennessee derives its name."

In this area of the Little Tennessee River the Tennessee Valley Authority, a wholly owned public corporation of the United States, began constructing the Tellico Dam and Reservoir Project in 1967, shortly after Congress appropriated initial funds for its development. Tellico is a multipurpose regional development project designed principally to stimulate shoreline development, generate sufficient electric current to heat 20,000 homes, and provide flatwater recreation and flood control, as well as improve economic conditions in "an area characterized by underutilization of human resources and outmigration of young people." Hearings on Public Works for Power and Energy Research Appropriation Bill, 1977, before a Subcommittee of the House Committee on Appropriations, 94th Cong., 2d Sess., pt. 5, p. 261 (1976). Of particular relevance to this case is one aspect of the project, a dam which TVA determined to place on the Little Tennessee, a short distance from where the river's waters meet with the Big Tennessee. When fully operational, the dam would impound water covering some 16,500 acres-much of which represents valuable and productive farmland-thereby converting the river's shallow, fast-flowing waters into a deep reservoir over 30 miles in length.

The Tellico Dam has never opened, however, despite the fact that construction has been virtually completed and the

2 See Brief for the Eastern Band of Cherokee Indians as Amicus Curiae 2. See also Mooney, Myths of the Cherokee, 19 Bureau of American Ethnology Ann. Rep. 11 (1900); H. Timberlake, Memoirs, 1756-1765 (Watauga Press 1927); A. Brewer & C. Brewer, Valley So Wild: A Folk History (East Tenn. Historical Soc. 1975).

Public Works Appropriation Act, 1967, 80 Stat. 1002, 1014.

Tellico Dam itself will contain no electric generators; however, an interreservoir canal connecting Tellico Reservoir with a nearby hydroelectric plant will augment the latter's capacity.

dam is essentially ready for operation. Although Congress has appropriated monies for Tellico every year since 1967, progress was delayed, and ultimately stopped, by a tangle of lawsuits and administrative proceedings. After unsuccessfully urging TVA to consider alternatives to damming the Little Tennessee, local citizens and national conservation groups brought suit in the District Court, claiming that the project did not conform to the requirements of the National Environmental Policy Act of 1969 (NEPA), 83 Stat. 852, 42 U. S. C. § 4321 et seq. After finding TVA to be in violation of NEPA, the District Court enjoined the dam's completion pending the filing of an appropriate environmental impact statement. Environmental Defense Fund v. TVA, 339 F. Supp. 806 (ED Tenn.), aff'd, 468 F. 2d 1164 (CA6 1972). The injunction remained in effect until late 1973, when the District Court concluded that TVA's final environmental impact statement for Tellico was in compliance with the law. Environmental Defense Fund v. TVA, 371 F. Supp. 1004 (ED Tenn. 1973), aff'd, 492 F. 2d 466 (CA6 1974).5

A few months prior to the District Court's decision dissolving the NEPA injunction, a discovery was made in the waters of the Little Tennessee which would profoundly affect the Tellico Project. Exploring the area around Coytee Springs, which is about seven miles from the mouth of the river, a University of Tennessee ichthyologist, Dr. David A. Etnier, found a previously unknown species of perch, the snail darter, or Percina (Imostoma) tanasi. This three-inch, tannish-colored fish,

5 The NEPA injunction was in effect some 21 months; when it was entered TVA had spent some $29 million on the project. Most of these funds have gone to purchase land, construct the concrete portions of the dam, and build a four-lane steel-span bridge to carry a state highway over the proposed reservoir. 339 F. Supp., at 808.

The snail darter was scientifically described by Dr. Etnier in the Proceedings of the Biological Society of Washington, Vol. 88, No. 44, pp. 469-488 (Jan. 22, 1976). The scientific merit and content of Dr. Etnier's

whose numbers are estimated to be in the range of 10,000 to 15,000, would soon engage the attention of environmentalists, the TVA, the Department of the Interior, the Congress of the United States, and ultimately the federal courts, as a new and additional basis to halt construction of the dam.

Until recently the finding of a new species of animal life would hardly generate a cause célèbre. This is particularly so in the case of darters, of which there are approximately 130 known species, 8 to 10 of these having been identified only in the last five years." The moving force behind the snail darter's sudden fame came some four months after its discovery, when the Congress passed the Endangered Species Act of 1973 (Act), 87 Stat. 884, 16 U. S. C. § 1531 et seq. (1976 ed.). This legislation, among other things, authorizes the Secretary of the Interior to declare species of animal life "endangered" and to

8

paper on the snail darter were checked by a panel from the Smithsonian Institution prior to publication. See App. 111.

"In Tennessee alone there are 85 to 90 species of darters, id., at 131, of which upward to 45 live in the Tennessee River system. Id., at 130. New species of darters are being constantly discovered and classified-at the rate of about one per year. Id., at 131. This is a difficult task for even trained ichthyologists since species of darters are often hard to differentiate from one another. Ibid.

• An "endangered species" is defined by the Act to mean "any species which is in danger of extinction throughout all or a significant portion of its range other than a species of the Class Insecta determined by the Secretary to constitute a pest whose protection under the provisions of this chapter would present an overwhelming and overriding risk to man." 16 U. S. C. § 1532 (4) (1976 ed.).

""The act covers every animal and plant species, subspecies, and population in the world needing protection. There are approximately 1.4 million full species of animals and 600,000 full species of plants in the world. Various authorities calculate as many as 10% of them—some 200,000-may need to be listed as Endangered or Threatened. When one counts in subspecies, not to mention individual populations, the total could increase to three to five times that number.'" Keith Shreiner, Associate Director and Endangered Species Program Manager of the U. S. Fish and Wildlife Service, quoted in a letter from A. J. Wagner, Chairman, TVA, to

identify the "critical habitat" of these creatures. When a species or its habitat is so listed, the following portion of the Act-relevant here becomes effective:

"The Secretary [of the Interior] shall review other programs administered by him and utilize such programs in furtherance of the purposes of this chapter. All other Federal departments and agencies shall, in consultation with and with the assistance of the Secretary, utilize their authorities in furtherance of the purposes of this chapter by carrying out programs for the conservation of endangered species and threatened species listed pursuant to section 1533 of this title and by taking such action necessary to insure that actions authorized, funded, or carried out by them do not jeopardize the continued existence of such endangered species and threatened species or result in the destruction or modification of habitat of such species which is determined by the Secretary, after consultation as appropriate with the affected States, to be critical." 16 U. S. C. § 1536 (1976 ed.) (emphasis added).

Chairman, House Committee on Merchant Marine and Fisheries, dated Apr. 25, 1977, quoted in Wood, On Protecting an Endangered Statute: The Endangered Species Act of 1973, 37 Federal B. J. 25, 27 (1978).

9 The Act does not define "critical habitat," but the Secretary of the Interior has administratively construed the term:

"Critical habitat' means any air, land, or water area (exclusive of those existing man-made structures or settlements which are not necessary to the survival and recovery of a listed species) and constituent elements thereof, the loss of which would appreciably decrease the likelihood of the survival and recovery of a listed species or a distinct segment of its population. The constituent elements of critical habitat include, but are not limited to: physical structures and topography, biota, climate, human activity, and the quality and chemical content of land, water, and air. Critical habitat may represent any portion of the present habitat of a listed species and may include additional areas for reasonable population expansion." 43 Fed. Reg. 874 (1978) (to be codified as 50 CFR § 402.02).

In January 1975, the respondents in this case 10 and others petitioned the Secretary of the Interior 11 to list the snail darter as an endangered species. After receiving comments from various interested parties, including TVA and the State of Tennessee, the Secretary formally listed the snail darter as an endangered species on October 8, 1975. 40 Fed. Reg. 47505– 47506; see 50 CFR § 17.11 (i) (1976). In so acting, it was noted that "the snail darter is a living entity which is genetically distinct and reproductively isolated from other fishes." 40 Fed. Reg. 47505. More important for the purposes of this case, the Secretary determined that the snail darter apparently lives only in that portion of the Little Tennessee River which would be completely inundated by the reservoir created as a consequence of the Tellico Dam's completion. Id., at 47506.12

10 Respondents are a regional association of biological scientists, a Tennessee conservation group, and individuals who are citizens or users of the Little Tennessee Valley area which would be affected by the Tellico Project.

11 The Act authorizes "interested person[s]" to petition the Secretary of the Interior to list a species as endangered. 16 U. S. C. § 1533 (c) (2) (1976 ed.); see 5 U. S. C. § 553 (e) (1976 ed.).

12 Searches by TVA in more than 60 watercourses have failed to find other populations of snail darters. App. 36, 410-412. The Secretary has noted that "more than 1,000 collections in recent years and additional earlier collections from central and east Tennessee have not revealed the presence of the snail darter outside the Little Tennessee River." 40 Fed. Reg. 47505 (1975). It is estimated, however, that the snail darter's range once extended throughout the upper main Tennessee River and the lower portions of its major tributaries above Chattanooga-all of which are now the sites of dam impoundments. See Hearings on Public Works for Water and Power Development and Energy Research Appropriation Bill, 1978, before a Subcommittee of the House Committee on Appropriations, 95th Cong., 1st Sess., pt. 4, pp. 240-241 (1977) (statement of witness for TVA); Hearings on Endangered Species Act Oversight, before the Subcommittee on Resource Protection of the Senate Committee on Environment and Public Works, 95th Cong., 1st Sess., 291 (1977); App. 139.