Vulnerable species are at risk of becoming extinct in the wild or extinct. The IUCN currently identifies over 10,000 species as vulnerable. For a species to be considered vulderable it must meet any of the following criteria:
- A taxon’s population size is reduced by 50 percent or more over 10 years or three generations, whichever is longer, and scientists understand that the reduction causes are reversible and have stopped. For example, let’s pretend there is a bird species that traditionally had a population of 2000. Over 10 years, it drops to 1000 because a logging company demolished its habitat. If lawmakers establish regulations that bar the logging company from continuing to fell trees in the area, then the IUCN will list the bird species as “endangered” because they understand the reason for the decline, and it is stopped.
- A taxon’s population size is reduced by 30 percent or more over 10 years or three generations, whichever is longer. However, conservationists don’t understand the reduction cause or know if it is reversible. For example, let’s say there is a bird species that traditionally had a population size of 2000. Over 10 years, it drops to 1400. Scientists, however, can’t figure out why they’re dying off. In this case, the IUCN would list it as “endangered” because the decimation is evident, but it can’t figure out why.
- A taxon’s population size is reduced by 30 percent or more over 10 years or three generations, whichever is longer, and the animal is also battling habitat shrinkage or another threat.
The area where a species can live is reduced to 20,000 square kilometers or less, or the area where it currently and actually occupies is reduced to 2,000 square kilometers, and at least two of the following criteria are also true:
- The population is not known to exist at more than 10 locations.
- Scientists observe or predict that the habitat in question will continue to shrink or be degraded, and there’s also a decline in subpopulations or the number of reproducing adults.
- Scientists observe extreme fluctuations in the number of locations, subpopulations, or the number of reproducing adults.
Dangerously Low Number of Adults
- A taxon’s population only has 10,000 or fewer adults left, and a 10 percent decline is anticipated within 10 years or three generations, whichever is longer. If none of the taxon’s subpopulations contain more than 1,000 adults, or all the adults live in one subpopulation.
- Scientists observe extreme fluctuations in the number of mature adults in a taxon’s population.
Dangerously Low Overall Population Size
- Only 1,000 or fewer individuals of a taxon remain.
- A population with a viable but restricted habitat area is vulnerable to human activities within a very short period and thus may become critically endangered or extinct in the near future.
Expected Rapid Decline
Research indicates that there’s a 10 percent or greater chance that the taxon will be extinct in the wild within 100 years