Because of European explorers, the slave trade became focused on the New World rather than moving slaves across the Sahara. Most of the slaves were sent to cotton, sugar, and tobacco plantations in the Americas. Cotton, sugar, and tobacco cash crops, being very profitable for the Europeans. Slaves were treated especially harshly in the sugar plantations of the tropics, where it was believed that working them to death was cheaper than keeping them alive. Slaves were treated better in North America, where not as many cash crops were produced. As the Europeans explored the New World, they established colonies and plantations. There, they grew very profitable goods such as sugar, tobacco, and cotton. Since these crops are tropical, most of the plantations where they grew were established in the tropics of the Americas. The richest sugar colony, for example, was located in the Caribbean, in Haiti, to be specific. With the rise of these plantations and colonies, there was a need for labor. The Portuguese, who had explored much of the African coast, were the first to begin the Atlantic slave trade. About 2.4 million slaves were brought on ships to the Greater Antilles, the region around Cuba and Haiti. North America also farmed tobacco and cotton. At first indentured servants were used to work on plantations. However, slaves from Africa became a cheaper source, and so they were imported to labor. Not as many slaves were imported to North America as to the tropics of the Americas, probably because the slaves in North America had high birth rates. These high birth rates were likely because slaves in North America were treated better than in the tropics, where a main philosophy of plantation owners was to work the slaves until they died. Despite the trading of slaves across the Atlantic, trade across the Sahara desert still continued, with around 1 million slaves being traded to places like Cairo, Tripoli, and Tunis.