Answer:
If you're asking about the decline in the indigenous population after the arrival of European settlers in the Americas, then five factors are as follows:
1. Diseases brought by Europeans decimated the indigenous population, since they had no natural immunity to viruses such as smallpox.
2. Many indigenous people were killed by the settlers, as they where no match for the guns and horses that the Europeans brought.
3. Many natives where forced into slavery and terrible living conditions, causing further death.
4. In some cases, the European conquers turned the indigenous tribes against each other, inciting further violence.
5. The displacement of Native Americans by settlers as they pushed further and further into the continent also resulted in a decline in the population.
