Much of the state's lands were formed from sediment washed down the Mississippi River, leaving enormous deltas and vast areas of coastal marsh and swamp.[self-published source] These contain a rich southern biota; typical examples include birds such as ibis and egrets. There are also many species of tree frogs, and fish such as sturgeon and paddlefish. In more elevated areas, fire is a natural process in the landscape, and has produced extensive areas of longleaf pine forest and wet savannas. These support an exceptionally large number of plant species, including many species of orchids and carnivorous plants. Louisiana has more Native American tribes than any other southern state, including four that are federally recognized, ten that are state recognized, and four that have not yet received recognition.
Some Louisiana urban environments have a multicultural, multilingual heritage, being so strongly influenced by a mixture of 18th-century French, Haitian, Spanish, Native American, and African cultures that they are considered to be exceptional in the US. Before the American purchase of the territory in 1803, the current Louisiana State had been both a French colony and for a brief period, a Spanish one. In addition, colonists imported numerous African people as slaves in the 18th century. Many came from peoples of the same region of West Africa, thus concentrating their culture. In the post-Civil War environment, Anglo-Americans increased the pressure for Anglicization, and in 1921, English was for a time made the sole language of instruction in Louisiana schools before a policy of multilingualism was revived in 1974. There has never been an official language in Louisiana, and the state constitution enumerates "the right of the people to preserve, foster, and promote their respective historic, linguistic, and cultural origins."