Answer:
The many original diaries, letters, books, and reports by eyewitnesses of Indian fire use from the 1600's to the 1900's have yielded considerable evidence that American Indians did use fire to change ecosystems.
Step-by-step explanation:
The main idea of Introduction to Aboriginal Fire Use in North America is that North American indigenous peoples intentionally used fire to shape and control the landscape. That fact helps us understand how conditions in our ecosystems today were affected by people in the past.
The first sentence of the section named Complex Burning Patterns is the following: The many original diaries, letters, books, and reports by eyewitnesses of Indian fire use from the 1600's to the 1900's have yielded considerable evidence that American Indians did use fire to change ecosystems. This is the sentence that reflects the main idea of the entire text.