What Does the Term 'Endangered Species' Mean?

An endangered species is a species of wild animal or plant that is in danger of extinction throughout all or a significant portion of its range. A species is considered threatened if it is likely to become endangered within the foreseeable future.

What Is the Difference Between Threatened and Endangered Species?

According to the U.S. Endangered Species Act:

• "Endangered" refers to a species that is in danger of extinction throughout all or a significant portion of its range.
• "Threatened" refers to a species that is likely to become endangered within the foreseeable future throughout all or a significant portion of its range.

On the International Union for Conservation of Nature and Natural Resources (IUCN) Red List, "threatened" is a grouping of 3 categories:

• Critically Endangered
• Endangered
• Vulnerable

What Factors Cause a Species to Become Endangered?

• Destruction, modification, or restriction of habitat resulting from human activity such as agriculture, urban development, mining, deforestation, and pollution
• Human exploitation of a species for commercial, recreational, scientific, educational, or other purposes that results in critically diminished population numbers
• Competition and/or displacement by invasive species
• Disease or predation by other animals to the extent that populations decline significantly

Who Decides That a Species Is Endangered?

• The IUCN is the global authority on endangered species determination. The IUCN compiles information from a network of conservation organizations to rate which species are most endangered, and this information is published in the IUCN Red List of Threatened Species.
• IUCN Regional Red Lists assess the risk of extinction to species in over 100 countries and regions around the world.
• In the United States, the U.S. Fish and Wildlife Service and the National Marine Fisheries Service work together to identify species that are in the greatest need of the protection provided by the Endangered Species Act.

How Does a Species Become Listed as Endangered?

The IUCN Red List conducts a detailed Assessment Process to evaluate extinction risk based on criteria such as rate of decline, population size, area of geographic distribution, and degree of population and distribution fragmentation.

Information included in the IUCN assessment is obtained and evaluated in coordination with IUCN Species Survival Commission specialist groups (authorities responsible for a specific species, group of species, or geographic area). Species are categorized and listed as followed:

• Extinct (EX) - No individuals remaining.
• Extinct in the Wild (EW) - Known only to survive in captivity, or as a naturalized population outside its historic range.
• Critically Endangered (CR) - Extremely high risk of extinction in the wild.
• Endangered (EN) - Very high risk of extinction in the wild.
• Vulnerable (VU) - High risk of extinction in the wild.
• Near Threatened (NT) - Likely to become endangered in the near future.
• Least Concern (LC) - Lowest risk. Does not qualify for a more at risk category. Widespread and abundant taxa are included in this category.
• Data Deficient (DD) - Not enough data to make an assessment of its risk of extinction.
• Not Evaluated (NE) - Has not yet been evaluated against the criteria.

Federal Listing Process

Before an animal or plant species in the United States can receive the protection from the Endangered Species Act, it must first be added to the List of Endangered and Threatened Wildlife or the List of Endangered and Threatened Plants.

A species is added to one of these lists via a petition process or a candidate assessment process. By law, any person may petition either the Secretary of the Interior or the Secretary of Commerce (depending on which agency has jurisdiction) to add a species to or remove a species from the lists of endangered and threatened species. The candidate assessment process is then conducted by biologists from either the U.S. Fish and Wildlife Service or the National Oceanic and Atmospheric Administration's National Marine Fisheries Service.