Barbados situated just east of the Caribbean Sea, is an independent island nation in the western Atlantic Ocean. At roughly 13° North of the equator and 59° West of the prime meridian, the country lies in the southern Caribbean region, where it is considered a part of the Lesser Antilles island-chain. Its closest island neighbours are Saint Vincent & the Grenadines and Saint Lucia to the west. To the south lies Trinidad and Tobago—with which Barbados now shares a fixed official maritime boundary and also the South American mainland. Barbados's total land area is about 430 square kilometres and is primarily low-lying, with some higher regions in the country's interior. The geological composition of Barbados is thought to be of non-volcanic origin and is predominantly composed of limestone-coral formed by subduction of the South American plate colliding with the Caribbean plate. The island's climate is tropical, with constant trade winds off the Atlantic Ocean serving to keep temperatures mild. Some more undeveloped areas of the country contain tropical woodland and scrubland. Other parts of the interior which contribute to the agriculture industry are dotted with large sugarcane estates and wide, gently sloping pastures, with views down to the coast.Barbados has one of the highest standards of living and literacy rates worldwide. Barbados's human development index ranking is consistently among the top 50 in the world. For example, in 2006, it was ranked 31st in the world, and third in the Americas, behind Canada and the United States.