Answer: They gave evidence to his assertion that forest logging was on the rise
Explanation:
John Muir was one of America's most famous environmentalists. He was known as the Father of National Parks due to his influence in the setting up of National Parks by the Federal Governments to protect forests and its inhabitants.
John Muir wrote a couple of articles on the need to preserve forests in the United States including ''Hunting Big Redwoods'' where he talked about how rare and old some of these trees were. He spoke of how people had began to cut trees in larger numbers and how more and more forests were now subjected to logging since the Colonists arrived in America.
The map supports his assertion by showing how there are more areas of forest being logged in 1920 than 270 years earlier in 1650.
