Final answer:
The arrival of Europeans in the Americas introduced diseases that devastated native populations and altered ecosystems via the Columbian Exchange.
Step-by-step explanation:
The arrival of Europeans to the Americas had several profound impacts on both the environment and the native societies. The introduction of European diseases, such as smallpox, to which the indigenous peoples had no immunity, caused massive mortality rates, particularly among the very young and the old.
This led to the loss of entire generations, along with their knowledge and traditions. The depopulation had cascading effects on the structure of native societies, economies, and the environment.
Furthermore, Europeans brought with them new flora and fauna, as part of what is known as the Columbian Exchange. This included crops and animals that would significantly alter the American landscape and ecosystems.
Plants and animals from the Americas likewise profoundly impacted European diets and agriculture. The European settlers also introduced new concepts of personal property and different warfare technologies, which led to changes in land use and contributed to conflict and the displacement of native peoples.
Collectively, these changes fundamentally transformed both continents, shaping a 'new world' that was neither fully European nor entirely native, but a complex mixture of the two, with lasting ecological and societal implications.