Final answer:
The word "advocate" in the given context means a person who actively supports or argues for the protection and conservation of nature.
Step-by-step explanation:
The word "advocate" as used in sentence 1 of the passage, "I want to be a vocal advocate for nature," refers to a person who actively supports or argues for a cause or policy. In this case, the teen hero wants to be a spokesperson for the environment, championing its protection and conservation. Not letting age be a deterrent, the teen exemplifies commitment to a cause by engaging in activities such as river cleanups and political outreach. These actions are reflective of the broader context where figures like John Muir and Rachel Carson have historically spoken out for the conservation of nature due to its inherent value and harmonious relationship with humanity. By advocating for nature, one aligns with the culture of conservation and the ethical standpoint that humans should live in harmony with rather than exploit the natural world.