The decline of native populations in the 1500s and 1600s was primarily due to the spread of European diseases, such as smallpox, measles, and influenza, which the indigenous people had not previously been exposed to and had not developed immunity against. Additionally, European colonization brought about conflicts and violence between European settlers and native populations, often resulting in warfare, displacement, and forced assimilation. Therefore, the most accurate answer to this question is "Europeans claimed the land and diseases spread."
Simple as that, look it up for more information.
Thanks,
Eddie Echevarria
#SP90