academic environmental studies   macalester college
The Endangered Species Act




How it works


Recovery Plans and Delisting

Critical Habitat

Habitat Conservation Plans

Controversy: Is the ESA Effective?

Criticism of the ESA--from both sides

 Is the ESA biologically unsound?

Private landowners


Links and References


Origins of the Endangered Species Act

Since President Richard M. Nixon signed the Endangered Species Act into law in 1973, it has not only been called one of the most important pieces of environmental legislation, but also one of the most controversial. From the snail darter controversy in the 1970s to the current debate surrounding the listing of the polar bear, the Endangered Species Act has come under fire sfrom every direction. Is the ESA biologically unsound? Does the Act encroach on private property rights? Are science and politics too close for comfort? It remains to be seen what will happen when the Act comes up for reauthorization, but many valuable lessons can be learned from case studies and previous legislation.

The Endangered Species Act, intended to protect species and “the ecosystems upon which they depend,” arose during an era of social and political engagement and environmental activism. Congress passed legislation first in 1966 to protect vertebrates and expanded its scope in 1969. In 1972, President Richard Nixon called for a comprehensive action plan, and on December 28, 1972, he signed the Act into law. The Act currently protects plants and invertebrates, as well as vertebrates. It does not protect fungi.

Importance of Biodiversity 

The term "biodiversity" refers to the variety of life forms and ecosystems present on the Earth, as well as to the variability of genetic makeup. It also refers to interactions among these life forms. The basic value of biodiversity was identified by the National Research Council: "The Earth's non-human biota are crucial to humans' long-term survival. We depend on the photosynthetic capability of green plants for the oxygen that we breathe for virtually all our food and energy requirements." Biodiversity is also important for other reasons, among them ecological, economic and cultural. In addition to contributing to the world's carbon and oxygen cycles, ecologically, biodiversity also contributes to the water cycle, the nitrogen cycle and the energy cycle. Each one is crucial for life to persist, moderating the Earth's temperature and maintaining a hospitable climate, and providing us with food, clean water and breathable air. Biodiversity also has immense economic value, from food and drink to medicine and industrial materials. Conservation biologists also argue for the intrinsic value of biodiversity. Humans, the say, are a part of nature.  In his seminal work, A Sand Country Almanac (1949), Aldo Leopold argues,

We know now what was unknown to all the preceding caravan of generations: that men are only fellow-voyagers with other creatures in the odyssey of evolution... Above all we should, in the century since Darwin, have come to know that man, while now captain of the adventuring ship, is hardly the sole object of its quest, and that prior assumptions to this effect arose from the simple necessity of whistling in the dark.

Rachel Carson, author of Silent Spring (1962), argues for the existence of a species merely because of its very presence in the long history of evolution when she asks, "Can any civilization wage relentless war on life without destroying itself and without losing the right to be called civilized?"

The processes of endangerment, recovery and extinction

All species, regardless of population size or how fast their population is growing, are subject to extinction. According to Beissinger and Perrine, "catastrophic events, such as prolonged or intense droughts, floods, freezes, or even thermonuclear war or a meteor slamming into Earth may result in the death of all individuals of a population or species" (52). Extinction and extirpation (local extinction) has been occurring on varying scales for the entire history of the Earth. According to the most recent estimates, the 3-10 million species currently on Earth only represents 2-4 percent of all the species that have ever lived (Jablonski 1991, 1995).

Biologists often divide the process of endangerment into three phases (see right). At some point in its history, a species will likely be at its carrying capacity, K. As the species' numbers drop, it goes into the Declining Phase. Different populations may become very small throughout a species' range, and individually they may go extinct or recover. The population's viability may decline as the result of a steady loss of genetic diversity during this Bottleneck Phase. The smaller the bottleneck size and the longer it stays in the bottleneck phase, the greater loss of genetic diversity the species will experience. Ultimately, the population will either enter the Recovery Phase or go extinct.

Extinction events are usually divided into two general types: deterministic and stochastic. Deterministic forces include 'habitat destruction, overharvesting, or pollution," among others (Beissinger and Perrine, 53). Stochastic factors are chance events. There are four main types of stochastic that can affect the likelihood of extinction: genetic stochasticity, demographic stochasticity, environmental stochasticity, and catastrophe (Shaffer 1981). According to Beissinger and Perrine, “genetic stochasticity refers to the mortality and loss of fitness that can result from the expression of deleterious recessive genes resulting from inbreeding of close relatives, and the loss of genetic diversity that can occur...from genetic drift.' Demographic stochasticity is 'the chance that normal birth and death processes will become unbalanced when populations are reduced in size.” Environmental stochasticity "refers to the year-to-year variation in birth and death rates that naturally occurs, often as a result of changes in resources or weather." Catastrophes, like hurricanes, fire, extreme cold can affect populations of any size. The Endangered Species Act primarily concerns itself with deterministic events, but there is more and more pressure from conservation biologists to consider environmental stochasticity as well as catastrophic events in the protection of biodiversity.

Politics and the ESA

The ESA protects endangered animals from any governmental agency, corporation or citizen from taking' (killing or harming) without a permit. According to Section 7(a).2., federal agencies are forbidden from authorizing, funding, or carrying out any action that may "jeopardize the continued existence of” an endangered species. The listed species' habitat is also protected under the Act, a provision that requires "critical habitat" be designated, including areas necessary for the recovery of the species (Section 3.5.A.). Federal agencies are also forbidden from authorizing, funding, or carrying out any action which "destroys or adversely modifies" critical habitat (also part of Section 7(a).2.).

The Endangered Species Act is administered by the United States Fish and Wildlife Service (USFWS), who have responsibility for freshwater fish and all other species, and NOAA Fisheries, who is responsible for marine species. Species occurring in both habitats, like sea turtle, are jointly managed. Section 11 of the Act allows citizens to sue the government to enforce the law. In such a situation, each of the branches of the United States government may intervene, including Congress, the Supreme Court and the President.

"Nothing is more priceless and more worth of preservation than the rich array of animal life with which our country has been blessed. It is a many-faceted treasure, of value to scholars, scientists, and nature lovers alike, and it forms a vital part of the heritage we all share as Americans."
           -President Richard M. Nixon, as he signed Endangered Species Act into law, 1973

rachel carson             aldo

Rachel Carson and Aldo Leopold, proponents and scholars of biodiversity


adapted from Bessinger and Perrine


Macalester College · 1600 Grand Avenue, St. Paul, MN 55105  USA · 651-696-6000
Comments and questions to