他的写作和演讲提高了人们对保护自然的重要性的认识，并帮助建立了我们的国家公园系统。
His writing and speaking raised the awareness of the importance of conservation and helped bring about our national park system.
美国的国家公园就是分布于世界各地类似的系统中的典范，其理念就是在保护区内人类只是游客，而不能成为永久居民。
America's system of national parks, a model for similar set-ups around the world, was based on the idea of limiting human presence to passing visits, rather than permanent habitation.
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