What do we call a species whose numbers are so low that the species is at risk of extinction?

The term for a species whose numbers are so low that it faces a high risk of extinction is "endangered species." This classification is part of a wider system of categorizing species based on their conservation status, which helps in prioritizing efforts for their protection and recovery.

An endangered species typically has a population that has declined significantly, often due to habitat loss, overexploitation, disease, or environmental changes. This designation reflects an urgent need for conservation efforts to prevent extinction, often involving legal protections and resource allocation to ensure the survival of the species.

Other classifications, such as vulnerable or threatened species, indicate varying levels of risk, with vulnerable being less critical than endangered, and threatened encompassing any species that is likely to become endangered in the near future. The concept of at-risk species is a broader term that may encompass those that are vulnerable, threatened, or endangered but does not specify the immediate risk of extinction as clearly as "endangered" does.