The famous environmentalist whose biography focuses on their advocacy for the conservation of nature is John Muir. Known as the "Father of the National Parks," Muir played a critical role in the establishment of protected areas in the United States, including Yosemite National Park. His writings and activism helped raise public awareness about the importance of preserving natural landscapes. Muir’s biography often highlights his passion for the outdoors and his belief in the spiritual and ecological value of nature, inspiring future generations to engage in environmentalism.