Abstract
The Caspian Sea is the largest enclosed body of water in the world. The Caspian Sea has been isolated for so long and as a result, has high percentage of endemic species and the uniqueness of the biological diversity. Among Caspian species several are of conservation concern and have been included into the IUCN Red Book. Several factors are contributing to the decline of species in the region. These factors include natural processes such as sea level fluctuation and human activities such as pollution, overexploitation of resources and the impacts of introduced species. The current paper investigated threats to the biodiversity of the Caspian and extracted threatened species in the region from the latest IUCN Red List (IUCN, 2007). Species with economical values such as sturgeons and Caspian seal are specially endangered due to over exploitation, poaching and pollution. Among migratory birds, species like Siberian Crane, White-headed Duck and Red-Breasted Goose are of endangered bird species in the region. In order to improve the environment of the Caspian Sea, the countries that share the benefits need to work together and develop a set of actions to protect the biodiversity of the Caspian and its ecosystem against the environmental problems.