As the British North American colonies developed however, it was not uncommon for the elite aristocracy to deny their indentured servants the land they were promised in their contracts. This created an array of issues as the former indentured servants began to defy the local colonial governments and occupy native land. The colonial aristocracy felt threatened by the newly freed servants demand for land and quickly realized the problems of indentured servitude. Landowners then turned to African slaves as a more profitable and ever-renewable source of labor; considering that the slaves were in fact immune to most diseases and capable of working in harsh climates, growing labor-intensive crops such as tobacco, sugar, rice and indigo. As a result, the shift from the use of white indentured servants to African slavery had begun. The slave trade developed as a part of the trans-Atlantic interactions between the British North American colonies and Europe, and Africans were transported primarily across the Middle Passage. By the eighteenth century, slavery was an accepted form of labor throughout the colonies and was particularly commonplace in the south. African slaves quickly became the preferred source of labor and played a pivotal role in the Atlantic slave trade