According to UNESCO, the site is of universal importance because of its biodiversity with rich and distinct flora and fauna: 37% of Socotra’s 825 plant species, 90% of its reptile species and 95% of its land snail species do not occur anywhere else in the world. The site also supports globally significant populations of land and sea birds (192 bird species, 44 of which breed on the islands while 85 are regular migrants), including a number of threatened species. The marine life of Socotra is also very diverse, with 253 species of reef-building corals, 730 species of coastal fish and 300 species of crab, lobster and shrimp.
The main island, Socotra, is 1,400 square miles (a bit larger than Hong Kong but smaller than Rhode Island). It consists of a jagged many-peaked granite mountain range, Jabal Haggeher, which rise to 1,526 meters in Jabal Skand, steeply on the north side and more gently, with six parallel valleys, on the south; limestone plateaus in the east and west, and an interior basin plain.
Writing about the island for The New York Times in 2007, Alan Burdick noted: "Some 250 million years or more ago, when all the planet’s major landmasses were joined and most major life-forms were just a gleam in some evolutionary eye, Socotra already stood as an island apart. Ever since, it has been gathering birds, seeds and insects off the winds and cultivating one of the world’s most unusual collections of organisms. In addition to frankincense, Socotra is home to myrrh trees and several rare birds. Its marine life is a unique hybrid of species from the Red Sea, the Indian Ocean and the western Pacific. In the 1990s, a team of United Nations biologists conducted a survey of the archipelago’s flora and fauna. They counted nearly 700 endemic species, found nowhere else on earth; only Hawaii and the Galapagos Islands have more impressive numbers."
The Galapagos Islands have a total of 543 plant species, including 229 endemic species. Socotra, in comparison, has 825 plant species, 307 of which are endemic. Galapagos has 57 bird species and 460 fish species. Socotra has 192 bird species and 730 fish species. Socotra is also rich in coral species (283, compared with Australia's Great Barrier Reef's 400 species).
"Socotra," UNESCO concludes, "is not suffering from many of the threats affecting other oceanic islands. This refl ects a number of factors, including the relative isolation of Socotra (until 1989 the island was also politically isolated) and the relatively low resident population on the island. The total population of Socotra is 50,000 (out of 22 million in Yemen). People and nature have a very close relationship on Socotra. Traditional patterns of use involving nomadic herding have evolved over thousands of years and have strongly infl uenced the biodiversity of Socotra."