The speaker of "Crossing Brooklyn Ferry" is blown-away by, like, everything he sees. He's like a small child in a shopping mall: "Wow! An electric nose-hair trimmer!" He doesn't divide the world up into good and bad, natural and unnatural. Everything fits together as it should. He even thinks the smoky chimneys of the foundries deserve verses of praise. And he comes close to losing it in his raptures of the sea gulls. What we're trying to say is: he's a really, really happy guy.
The speaker makes no distinction between "Man" and "Nature." He believes that man's works are a part of nature.