years, sugar cane cultivation in this region was the mainstay of Brazil's economy, being superseded only when coffee production developed in the late 19th century. Sugar cane is cultivated on large estates whose owners maintain tremendous political influence. Agreste Since the escarpment does not generate any further rainfall on its slopes from the lifting of the trade winds, annual rainfall decreases steadily inland. After a relatively short distance, there is no longer enough rainfall to support tropical rainforest, especially since the rainfall is extremely erratic from year to year. This transitional zone is known as the agreste and because it is located on the steep escarpment, was not generally used whilst flatter land was abundant. Today, with irrigation water available, however, the agreste, as its name suggest, is a major farming region. Despite containing no major city, it contains well developed medium large cities such as Caruaru, Campina Grande and Arapiraca. Sertão ("Backlands") In Portuguese, the word sertão (, meaning "backcountry" or "outback") first referred to the vast hinterlands of Asia and South America that Lusitanian explorers encountered. In Brazil, the geographical term referred to backlands away from the Atlantic coastal regions where the Portuguese first settled in South America in the early sixteenth century. Geographically, the Sertão consists mainly of low uplands that form part of the Brazilian Highlands. Most parts of the sertão are between 200 and 500 meters above sea level, with higher elevations found on the eastern edge in the Planalto da Borborema, where it merges into a sub-humid region known as agreste, in the Serra da Ibiapaba in western Ceará and in the Serro do Periquito of central Pernambuco. In the north, the Sertão extends to the northern coastal plains of Rio Grande do Norte state, whilst in the south it fades out in the northern fringe of Minas Gerais. Because the Sertão lies close to the equator, temperatures remain nearly uniform throughout the year and are typically tropical, often extremely hot in the west. However, the sertão is distinctive in its low rainfall compared to other areas of Brazil. Because of the relatively cool temperatures in the South Atlantic Ocean, the intertropical convergence zone remains north of the region for most of the year. Consequently, conditions are very dry for most of the year. Although annual rainfall averages between 500 and 800 millimeters over most of the sertão and 1300 millimeters on the northern