Final answer:
The abolition of the encomienda system resulted in the growth of the transatlantic slave trade as Spanish and Portuguese settlers sought a new labor source for their plantations and mines.
Step-by-step explanation:
The long-term consequence of the Spanish abolishing the encomienda system was not the economic prosperity in the colonies, the rise of indigenous leadership, or the decline of Spanish influence in the Americas, but rather C) The growth of the transatlantic slave trade. The encomienda system had subjected Indigenous peoples to severe labor conditions but proved to be an unreliable labor source due to high mortality from disease and mistreatment. Consequently, to maintain the labor-intensive agricultural and mining operations, particularly on sugar cane plantations, the Spanish and Portuguese turned to the African slave trade as an alternative source for robust and plentiful labor, laying the foundations of a race-based slavery system in the New World.