Tigris–Euphrates river system through the central plain and combine at Al-Qurnah to form the Shatt al-Arab and discharge into the Persian Gulf. The region has historical importance as part of the Fertile Crescent region, in which civilization is believed to have first emerged. The ecoregion is characterized by two large rivers, the Tigris and Euphrates. The rivers have several small tributaries which feed into the system from shallow freshwater lakes, swamps, and marshes, all surrounded by desert. The hydrology of these vast marshes is extremely important to the ecology of the entire upper Persian Gulf. Historically, the area is known as Mesopotamia. As
Euphrates it survives due to human interference, research suggests that the Euphrates Valley would have supported a riverine forest. Species characteristic of this type of forest include the Oriental plane, the Euphrates poplar, the tamarisk, the ash and various wetland plants. Among the fish species in the Tigris–Euphrates basin, the family of the Cyprinidae are the most common, with 34 species out of 52 in total. Among the Cyprinids, the mangar has good sport fishing qualities, leading the British to nickname it "Tigris salmon." The "Rafetus euphraticus" is an endangered soft-shelled turtle that is limited to the Tigris–Euphrates river system. The