John Muir was the famous botanist and conservationist known for his work in the field of ecology. As an advocate for the preservation of natural landscapes, Muir played a significant role in the establishment of national parks in the United States, particularly Yosemite. His writings and activism helped spur the American conservation movement, emphasizing the importance of nature to human well-being. Muir's legacy continues to inspire environmental stewardship and appreciation for the natural world.