Who was the environmental activist who played a critical role in protecting California's forests?

The individual who played a critical role in protecting California's forests is John Muir. He was a prominent naturalist and conservationist in the late 19th and early 20th centuries who advocated for the preservation of the wilderness, particularly in the Sierra Nevada region. Muir's efforts led to the establishment of several national parks, including Yosemite and Sequoia, and he co-founded the Sierra Club, which has been instrumental in environmental conservation. His extensive writings and passionate advocacy helped raise awareness about the importance of preserving natural landscapes for future generations. While Julia Butterfly Hill is known for her activism in the late 20th century, particularly for her efforts to save a single redwood tree in California, she did not have the same extensive impact on forest preservation as Muir. Rachel Carson, though a significant environmental figure for her work on pesticide issues, focused primarily on marine and agricultural ecosystems rather than forests. David Brower was also an influential environmentalist, but he built upon the foundations laid by activists like Muir. Thus, John Muir is the most fitting choice for his foundational contributions to the protection of California's forests.