1. The period of the earliest Americans:
Early American settlers and colonizers had negative, long lasting effects on many ecosystems. They brought with them new organisms that weren’t native to the area and in turn eliminated other native species. They also carried diseases that the native population wasn’t immune to, harming many of the indigenous communities as well. They quickly learned to look toward new plants for useful recourses, such as food, medicine, and building materials.
I hope this helps :) you can reword it however you need/want