Sustainability of flora and fauna is related to the concept of biological diversity, or biodiversity.

Biodiversity is the principle which seeks to preserve for posterity the species of flora and fauna in an ecosystem.

Loss of biodiversity leads to ecological unsustainability.

Species extinction leads to loss of biodiversity.

Species are listed as "endangered" to avoid extinction.

The International Union for the Conservation of Nature (IUCN) maintains a website listing the status of endangered species.