Endangered Species Categories

The United States passed the Endangered Species Act (ESA) in 1973 and the Marine Mammal Protection Act (MMPA) in 1972. The ESA and MMPA are fragmented among four different federal agencies. The ESA is administered by two federal agencies, the United States Fish and Wildlife Service (FWS) and the National Oceanic and Atmospheric Administration (NOAA). NOAA handles marine species, and the FWS has responsibility over freshwater fish and all other species. Species that occur in both habitats (e.g. sea turtles and Atlantic sturgeon) are jointly managed. The MMPA is administered by both the Department of Commerce (cetaceans-whales, porpoises, and dolphins, and pinnipeds-seals and sea lions; but not walruses) and the Department of the Interior (sea otters, polar bears, walruses, and manatees).

IUCN (International Union for Conservation of Nature and Natural Resources) was founded by the United Nations in 1948 (IUCN, the International Union for Conservation of Nature). It is composed of 86 countries, plus 120 government agencies, 902 NGO's (non-governmental agencies), and more than 10,000 scientists and experts from 147 countries. Headquarters are in Switzerland. The IUCN's mission is to influence, encourage and assist societies throughout the world to conserve the integrity and diversity of nature and to ensure that any use of natural resources is equitable and ecologically sustainable. The IUCN Red List (IUCN Red List) is the world's most comprehensive inventory of the global conservation status of plant and animal species. It uses a set of criteria to evaluate the extinction risk of thousands of species and subspecies. These criteria are relevant to all species and all regions of the world. With its strong scientific base, the IUCN Red List is recognized as the most authoritative guide to the status of biological diversity. The overall aim of the Red List is to convey the urgency and scale of conservation problems to the public and policy makers, and to motivate the global community to try to reduce species extinctions.

The following description of the categories is simplified to give an idea of the qualifications for each category and how they differ. These descriptions are not complete; for more detailed information see page 17 at IUCN Red List Book. The first 3 categories are for species which are faced with global extinction and are all Threatened.

Critically Endangered (CR): at extremely high risk for Extinct in the Wild

• >90% decrease in the number living in the last 10 years or the last 3 generations, where causes are reversible and understood, and have ceased; or an 80% decrease in number where the causes are either reversible, understood, or have ceased
• Geographic range is <38.6 square miles (half the size of Washington, D.D.), or occupancy is <3.8 square miles; with continuing decline or extreme fluctuations, or the location is severely fragmented
• The population is less than 250 mature individuals and has either decreased 25 % in the last 3 years or the last one generation; or the population is less than 50 mature individuals.
• Probability of extinct in the wild is at least 50% within 10 years or 3 generations.

Endangered (EN): at a very high risk for Extinct in the Wild

• >70% decrease in the number living in the last 10 years or the last 3 generations, where causes are reversible and understood, and have ceased; or a 50% decrease in number where the causes are either reversible, understood, or have ceased
• Geographic range is <1,930 square miles (slightly bigger than Rhode Island 1,545 square miles) and less than 5 locations, or occupancy is <193 square miles; with continuing decline or extreme fluctuations, or the location is severely fragmented
• The population is less than 2,500 mature individuals and has either decreased 20 % in the last 5 years or the last two generations; or the population is less than 250 mature individuals.
• Probability of extinct in the wild is at least 20% within 20 years or 5 generations.

Vulnerable (VU): at a high risk for Extinct in the Wild

• >50% decrease in the number living in the last 10 years or the last 3 generations, where causes are reversible and understood, and have ceased; or a 30% decrease in number where the causes are either reversible, understood, or have ceased
• Geographic range is <7,722 square miles (smaller than New Jersey 8,721 square miles) and less than 10 locations, or occupancy is <772 square miles; with continuing decline or extreme fluctuations, or the location is severely fragmented
• The population is less than 10,000 mature individuals and has either decreased 10% in the last 10 years or the last three generations; or the population is less than 1,000 mature individuals.
• Probability of extinct in the wild is at least 10% within 100 years.

Near Threatened (NT):

• These species are close to threatened in the near future, or would be without specific ongoing conservation measures, but does not qualify for CR, EN, or VU.

Least Concern:

• These species have been evaluated and been determined to not qualify for CR, EN, VU, or NT, and have a low risk of extinction. The species is widespread and abundant.

Data Deficient

• These species have insufficient data to make a determination, but it is acknowledged that there is a possibility that additional data will show that the specie is threatened.

Summary of October 2008 IUCN Red List Findings

The 2008 Red List has 44,838 species listed which is believed to represent only 2.5% of the world's species (animal and plant).