The exploitation of the Caribbean landscape dates back to the Spanish conquistadors starting in the 1490s, who forced indigenous peoples held by Spanish settlers in encomienda to mine for gold. The more significant development came when Christopher Columbus wrote back to Spain that the islands were made for sugar development. The history of Caribbean agricultural dependency is closely linked with European colonialism which altered the financial potential of the region by introducing a plantation system. Much like the Spanish exploited indigenous labour to mine gold, the 17th century brought a new series of oppressors in the form of the Dutch, the English, and the French. By the middle of the 18th century sugar was Britain's largest import which made the Caribbean that much more important as a colony.