Critically endangered

Criteria

To be defined as critically endangered in the Red List, a species must meet any of the following criteria (A–E):

A) Reduction in population size based on any of the following:

1. An observed, estimated, inferred or suspected population size reduction of ≥ 90% over the last 10 years or three generations, whichever is the longer, where the causes of the reduction are reversible AND understood AND ceased, based on (and specifying) any of the following:

• a. direct observation
• b. an index of abundance appropriate for the taxon
• c. a decline in area of occupancy, extent of occurrence or quality of habitat
• d. actual or potential levels of exploitation
• e. the effects of introduced taxa, hybridisation, pathogens, pollutants, competitors or parasites.

2. An observed, estimated, inferred or suspected population size reduction of ≥ 80% occurred over the last 10 years or three generations, whichever is the longer, where the reduction or its causes may not have ceased OR may not be understood OR may not be reversible, based on (and specifying) any of (a) to (e) under A1.

B) Geographic range in the form of either B1 (extent of occurrence) OR B2 (area of occupancy) OR both:

1. Extent of occurrence estimated to be less than 100 km², and estimates indicating at least two of a-c:

• a. Severely fragmented or known to exist at only one location.
• b. Continuing decline, inferred, observed or projected, in any of the following:
  • i. extent of occurrence
  • ii. area of occupancy
  • iii. area, extent or quality of habitat
  • iv. number of locations or subpopulations
  • v. number of mature individuals
• c. Extreme fluctuations in any of the following:
  • i. extent of occurrence
  • ii. area of occupancy
  • iii. number of locations or subpopulations
  • iv. number of mature individuals

2. Area of occupancy estimated to be less than 10 km², and estimates indicating at least two of a-c:

• a. Severely fragmented or known to exist at only one location.
• b. Continuing decline, inferred, observed or projected, in any of the following:
  • i. extent of occurrence
  • ii. area of occupancy
  • iii. area, extent or quality of habitat
  • iv. number of locations or subpopulations
  • v. number of mature individuals
• c. Extreme fluctuations in any of the following:
  • i. extent of occurrence
  • ii. area of occupancy
  • iii. number of locations or subpopulations
  • iv. number of mature individuals

C) Population estimated to number fewer than 250 mature individuals and either:

1. An estimated continuing decline of at least 25% within ten years or three generations, whichever is longer, OR

2. A continuing decline, observed, projected, or inferred, in numbers of mature individuals AND at least one of the following (a-b):

• a. Population structure in the form of one of the following:
  • i. no subpopulation estimated to contain more than 50 mature individuals, OR
  • ii. at least 90% of mature individuals in one subpopulation
• b. Extreme fluctuations in the number of older individuals

D) Population size estimated to number fewer than 50 mature individuals.

E) Quantitative analysis showing the probability of extinction in the wild is at least 50% within 10 years or three generations, whichever is the longer.

Causes

The current extinction crisis is witnessing extinction rates that are occurring at a faster rate than that of the natural extinction rate. It has largely been credited towards human impacts on climate change and the loss of biodiversity. This is along with natural forces that may create stress on the species or cause an animal population to become extinct.

Currently, the biggest reason for species extinction is human interaction resulting in habitat loss. Species rely on their habitat for the resources needed for their survival. If the habitat gets destroyed, the population will see a decline in their numbers. Activities that cause loss of habitat include: pollution, urbanization, and agriculture. Another reason that plants and animals become endangered is due to the introduction of invasive species. Invasive species invade and exploit a new habitat for its natural resources as a method to outcompete the native organisms, eventually taking over the habitat. This can lead to either the native species' extinction or causing them to become endangered, which also eventually causes extinction. Plants and animals may also go extinct due to disease. The introduction of a disease into a new habitat can cause it to spread amongst the native species. Due to their lack of familiarity with the disease or little or even no resistance, the native species can die off.

Examples

There are thousands of species categorized as critically endangered, including over 4,000 animals. Some of the most notable and known examples of critically endangered animals include mammals like the Vaquita, Amur leopard, Saola, Sumatran orangutan and several species of pangolin; birds like the Kākāpō and California condor; fish like the Devils Hole pupfish; reptiles like the Hawksbill sea turtle and Yangtze giant softshell turtle; amphibians like the Axolotl, Chinese giant salamander and Panamanian golden frog; and arachnids like the peacock tarantula. The Wollemi pine is considered one of the most notable examples of critically endangered plants in the world.