If this is a multiple choice response or includes a passage, you forgot to attach it, which makes this much harder to answer; however, I can confidently state that both Ralph Waldo Emerson and Henry David Thoreau were heavily involved in advocating for protecting nature historically. Emerson was the leader of the transcendentalist movement and wrote many books and poems about nature. Thoreau was scientist and writer who wrote a novel about the connection between humankind and the natural world. Additionally, both men lived in Concord and reportedly were friends.
I hope this helps. If you edit your question to include any multiple choice answers or attached passages, I can give a more specific response.